Easy Magic With Electronics

8086mp

noreply@blogger.com (ASIF 007) — Wed, 05 Sep 2012 12:22:00 +0000

rchitecture of 8086

Unlike microcontrollers, microprocessors do not have inbuilt memory. Mostly Princeton architecture is used for microprocessors where data and program memory are combined in a single memory interface. Since a microprocessor does not have any inbuilt peripheral, the circuit is purely digital and the clock speed can be anywhere from a few MHZ to a few hundred MHZ or even GHZ. This increased clock speed facilitates intensive computation that a microprocessor is supposed to do.

We will discuss the basic architecture of Intel 8086 before discussing more advanced microprocessor architectures.

Internal architecture of Intel 8086:

Intel 8086 is a 16 bit integer processor. It has 16-bit data bus and 20-bit address bus. The lower 16-bit address lines and 16-bit data lines are multiplexed (AD0-AD15). Since 20-bit address lines are available, 8086 can access up to 2 20 or 1 Giga byte of physical memory.

The basic architecture of 8086 is shown below.

Fig 29.1 Basic Architecture of 8086 Microprocessor

The internal architecture of Intel 8086 is divided into two units, viz., Bus Interface Unit (BIU) and Execution Unit (EU).

Bus Interface Unit (BIU )

The Bus Interface Unit (BIU) generates the 20-bit physical memory address and provides the interface with external memory (ROM/RAM). As mentioned earlier, 8086 has a single memory interface. To speed up the execution, 6-bytes of instruction are fetched in advance and kept in a 6-byte Instruction Queue while other instructions are being executed in the Execution Unit (EU). Hence after the execution of an instruction, the next instruction is directly fetched from the instruction queue without having to wait for the external memory to send the instruction. This is called pipe-lining and is helpful for speeding up the overall execution process.

8086's BIU produces the 20-bit physical memory address by combining a 16-bit segment address with a 16-bit offset address. There are four 16-bit segment registers, viz., the code segment (CS), the stack segment (SS), the extra segment (ES), and the data segment (DS). These segment registers hold the corresponding 16-bit segment addresses. A segment address is the upper 16-bits of the starting address of that segment. The lower 4-bits of the starting address of a segment is always zero. The offset address is held by another 16-bit register. The physical 20-bit address is calculated by shifting the segment address 4-bit left and then adding that to the offset address.

For Example:

Code segment Register CS holds the segment address which is 4569 H
Instruction pointer IP holds the offset address which is 10A0 H
The physical 20-bit address is calculated as follows.

Segment address : 45690 H
Offset address :+ 10A0 H
Physical address : 46730 H

MICRO PROCESSORS

noreply@blogger.com (ASIF 007) — Wed, 05 Sep 2012 12:19:00 +0000

What is a Microcontroller?

A Microcontroller is a programmable digital processor with necessary peripherals. Both microcontrollers and microprocessors are complex sequential digital circuits meant to carry out job according to the program / instructions. Sometimes analog input/output interface makes a part of microcontroller circuit of mixed mode(both analog and digital nature).
A microcontroller can be compared to a Swiss knife with multiple functions incorporated in the same IC.

Fig. 1.1 A Microcontroller compared with a Swiss knife

Microcontrollers Vs Microprocessors

A microprocessor requires an external memory for program/data storage. Instruction execution requires movement of data from the external memory to the microprocessor or vice versa. Usually, microprocessors have good computing power and they have higher clock speed to facilitate faster computation.
A microcontroller has required on-chip memory with associated peripherals. A microcontroller can be thought of a microprocessor with inbuilt peripherals.
A microcontroller does not require much additional interfacing ICs for operation and it functions as a stand alone system. The operation of a microcontroller is multipurpose, just like a Swiss knife.
Microcontrollers are also called embedded controllers. A microcontroller clock speed is limited only to a few tens of MHz. Microcontrollers are numerous and many of them are application specific.

Development/Classification of microcontrollers (Invisible)

Microcontrollers have gone through a silent evolution (invisible). The evolution can be rightly termed as silent as the impact or application of a microcontroller is not well known to a common user, although microcontroller technology has undergone significant change since early 1970's. Development of some popular microcontrollers is given as follows.

Intel 4004	4 bit (2300 PMOS trans, 108 kHz)	1971
Intel 8048	8 bit	1976
Intel 8031	8 bit (ROM-less)	.
Intel 8051	8 bit (Mask ROM)	1980
Microchip PIC16C64	8 bit	1985
Motorola 68HC11	8 bit (on chip ADC)	.
Intel 80C196	16 bit	1982
Atmel AT89C51	8 bit (Flash memory)	.
Microchip PIC 16F877	8 bit (Flash memory + ADC)	.

Development of microprocessors (Visible)

Microprocessors have undergone significant evolution over the past four decades. This development is clearly perceptible to a common user, especially, in terms of phenomenal growth in capabilities of personal computers. Development of some of the microprocessors can be given as follows.

Intel 4004	4 bit (2300 PMOS transistors)	1971
Intel 8080 8085	8 bit (NMOS) 8 bit	1974
Intel 8088 8086	16 bit 16 bit	1978
Intel 80186 80286	16 bit 16 bit	1982
Intel 80386	32 bit (275000 transistors)	1985
Intel 80486 SX DX	32 bit 32 bit (built in floating point unit)	1989
Intel 80586 I MMX Celeron II III IV	64 bit	1993 1997 1999 2000
Z-80 (Zilog)	8 bit	1976
Motorola Power PC 601 602 603	32-bit	1993 1995

Bipolar Transister

noreply@blogger.com (ASIF 007) — Fri, 06 Aug 2010 14:25:00 +0000

The Common Base Configuration :

If the base is common to the input and output circuits, it is know as common base configuration as shown in fig. 1.

Fig. 1

For a pnp transistor the largest current components are due to holes. Holes flow from emitter to collector and few holes flow down towards ground out of the base terminal. The current directions are shown in fig. 1.

(I_E = I_C + I_B ).

For a forward biased junction, V_EB is positive and for a reverse biased junction V_CB is negative. The complete transistor can be described by the following two relations, which give the input voltage V_EB and output current I_C in terms of the output voltage (V_CB) and input current I_E.

V_EB = f₁(V_CB, I_E)
I_C= f₂(V_CB, I_E)

The output characteristic:

The collector current I_Cis completely determined by the input current I_E and the V_CB voltage. The relationship is given in fig. 2. It is a plot of I_C versus V_CB, with emitter current I_E as parameter. The curves are known as the output or collector or static characteristics. The transistor consists of two diodes placed in series back to back (with two cathodes connected together). The complete characteristic can be divided in three regions.

Figure 7.2

(1). Active region:

In this region the collector diode is reverse biased and the emitter diode is forward biased. Consider first that the emitter current is zero. Then the collector current is small and equals the reverse saturation current I_CO of the collector junction considered as a diode.
If the forward current I_B is increased, then a fraction of I_E ie. a_dcI_E will reach the collector. In the active region, the collector current is essentially independent of collector voltage and depends only upon the emitter current. Because a_dc is, less than one but almost equal to unity, the magnitude of the collector current is slightly less that of emitter current. The collector current is almost constant and work as a current source.
The collector current slightly increases with voltage. This is due to early effect. At higher voltage collector gathers in a few more electrons. This reduces the base current. The difference is so small, that it is usually neglected. If the collector voltage is increased, then space charge width increases; this decreased the effective base width. Then there is less chance for recombination within the base region.

(2). Saturation region:

The region to the left of the ordinate V_CB = 0, and above the I_E = 0, characteristic in which both emitter and collector junction are forward biased, is called saturation region.
When collector diode is forward biased, there is large change in collector current with small changes in collector voltage. A forward bias means, that p is made positive with respect to n, there is a flow of holes from p to n. This changes the collector current direction. If diode is sufficiently forward biased the current changes rapidly. It does not depend upon emitter current.

(3). Cut off region:

The region below I_E = 0 and to the right of V_CB for which emitter and collector junctions are both reversed biased is referred to cutoff region. The characteristics I_E = 0, is similar to other characteristics but not coincident with horizontal axis. The collector current is same as I_CO. I_CBO_CO. It means collector to base current with emitter open. This is also temperature dependent. is frequently used for I

The Input Characteristic:

In the active region the input diode is forward biased, therefore, input characteristic is simply the forward biased characteristic of the emitter to base diode for various collector voltages. fig. 3. Below cut in voltage (0.7 or 0.3) the emitter current is very small. The curve with the collector open represents the forward biased emitter diode. Because of the early effect the emitter current increases for same V_EB. (The diode becomes better diode).
When the collector is shorted to the base, the emitter current increases for a given V_EB since the collector now removes minority carriers from the base, and hence base can attract more holes from the emitter. This mean that the curve V_CB= 0, is shifted from the character when V_CB = open.

Fig. 3

Equivalent circuit of a transistor: (Common Base)

In an ideal transistor, a_dc= 1. This means all emitter electrons entering the base region go on to the collector. Therefore, collector current equals emitter current. For transistor action, emitter diode acts like a forward bias diode and collector diode acts like a current source. The equivalent circuits of npn and pnp transistors are shown in fig. 4. The current source arrow points for conventional current. The current source is controlled by emitter current.

Common Base Amplifier:

The common base amplifier circuit is shown in Fig. 1. The V_EE source forward biases the emitter diode and V_CC source reverse biased collector diode. The ac source v_in is connected to emitter through a coupling capacitor so that it blocks dc. This ac voltage produces small fluctuation in currents and voltages. The load resistance R_L is also connected to collector through coupling capacitor so the fluctuation in collector base voltage will be observed across R_L.
The dc equivalent circuit is obtained by reducing all ac sources to zero and opening all capacitors. The dc collector current is same as I_E and V_CB is given by
V_CB_CC_C_C. = V - I R

Fig. 1

These current and voltage fix the Q point. The ac equivalent circuit is obtained by reducing all dc sources to zero and shorting all coupling capacitors. r'_e represents the ac resistance of the diode as shown in Fig. 2.

Fig. 2

Fig. 3, shows the diode curve relating I_E and V_BE. In the absence of ac signal, the transistor operates at Q point (point of intersection of load line and input characteristic). When the ac signal is applied, the emitter current and voltage also change. If the signal is small, the operating point swings sinusoidally about Q point (A to B).
Fig .3
If the ac signal is small, the points A and B are close to Q, and arc A B can be approximated by a straight line and diode appears to be a resistance given by
If the input signal is small, input voltage and current will be sinusoidal but if the input voltage is large then current will no longer be sinusoidal because of the non linearity of diode curve. The emitter current is elongated on the positive half cycle and compressed on negative half cycle. Therefore the output will also be distorted.
r'_e is the ratio of ΔV_BE and Δ I_E and its value depends upon the location of Q. Higher up the Q point small will be the value of r' e because the same change in V_BE produces large change in I_E. The slope of the curve at Q determines the value of r'_e. From calculation it can be proved that.

In general, the current through a diode is given by

Where q is he charge on electron, V is the drop across diode, T is the temperature and K is a constant.
On differentiating w.r.t V, we get,

The value of (q / KT) at 25°C is approximately 40.
Therefore,
or,

To a close approximation the small changes in collector current equal the small changes in emitter current. In the ac equivalent circuit, the current �i_C' is shown upward because if �i_e' increases, then �i_C' also increases in the same direction.

Voltage gain:

Since the ac input voltage source is connected across r'_e. Therefore, the ac emitter current is given by

i_e = V_in / r'_e

or, V_in = ie r'_e
The output voltage is given by V_out = i_c (R_C || R_L)

Under open circuit condition v_out = i_c R_c

Fig. 4

Example-1

Find the voltage gain and output of the amplifier shown in fig. 4, if input voltage is 1.5mV.
Fig. 4
Solution:
The emitter dc current I E is given by
Therefore, emitter ac resistance =
or, A_V= 56.6
and, V_out = 1.5 x 56.6 = 84.9 mV

Example-2

Repeat example-1 if ac source has resistance R s = 100 W .

Solution:

The ac equivalent circuit with ac source resistance is shown in fig. 5.

Fig. 5

The emitter ac current is given by

or,

Therefore, voltage gain of the amplifier =

and, V_out = 1.5 x 8.71 =13.1 mV

Common Emitter Curves:

The common emitter configuration of BJT is shown in fig. 1.

Fig. 1
In C.E. configuration the emitter is made common to the input and output. It is also referred to as grounded emitter configuration. It is most commonly used configuration. In this, base current and output voltages are taken as impendent parameters and input voltage and output current as dependent parameters
V_BE = f₁ ( I_B, V_CE )
I_C = f₂( I_B, V_CE)

Input Characteristic:

The curve between I_B and V_BE for different values of V_CE are shown in fig. 2. Since the base emitter junction of a transistor is a diode, therefore the characteristic is similar to diode one. With higher values of V_CE_BE is zero and I_B is also zero. collector gathers slightly more electrons and therefore base current reduces. Normally this effect is neglected. (Early effect). When collector is shorted with emitter then the input characteristic is the characteristic of a forward biased diode when V

Fig. 2

noreply@blogger.com (ASIF 007) — Fri, 06 Aug 2010 14:23:00 +0000

Lecture - 6: Bipolar Transistor

When the emitter diode is forward biased and collector diode is reverse biased as shown in fig. 4 then one expect large emitter current and small collector current but collector current is almost as large as emitter current.

Fig. 4
When emitter diodes forward biased and the applied voltage is more than 0.7 V (barrier potential) then larger number of majority carriers (electrons in n-type) diffuse across the junction.
Once the electrons are injected by the emitter enter into the base, they become minority carriers. These electrons do not have separate identities from those, which are thermally generated, in the base region itself. The base is made very thin and is very lightly doped. Because of this only few electrons traveling from the emitter to base region recombine with holes. This gives rise to recombination current. The rest of the electrons exist for more time. Since the collector diode is reverse biased, (n is connected to positive supply) therefore most of the electrons are pushed into collector layer. These collector elections can then flow into the external collector lead.
Thus, there is a steady stream of electrons leaving the negative source terminal and entering the emitter region. The V_EB forward bias forces these emitter electrons to enter the base region. The thin and lightly doped base gives almost all those electrons enough lifetime to diffuse into the depletion layer. The depletion layer field pushes a steady stream of electron into the collector region. These electrons leave the collector and flow into the positive terminal of the voltage source. In most transistor, more than 95% of the emitter injected electrons flow to the collector, less than 5% fall into base holes and flow out the external base lead. But the collector current is less than emitter current.

Relation between different currents in a transistor:

The total current flowing into the transistor must be equal to the total current flowing out of it. Hence, the emitter current I_E is equal to the sum of the collector (I_C ) and base current (I_B). That is,

I_E = I_C + I_B
The currents directions are positive directions. The total collector current I_C is made up of two components.

1. The fraction of emitter (electron) current which reaches the collector ( a_dc I_E )

2. The normal reverse leakage current I_CO
a_dc is known as large signal current gain or dc alpha. It is always positive. Since collector current is almost equal to the I_E therefore αdc I_E varies from 0.9 to 0.98. Usually, the reverse leakage current is very small compared to the total collector current.

NOTE: The forward bias on the emitter diode controls the number of free electrons infected into the base. The larger (V_BE) forward voltage, the greater the number of injected electrons. The reverse bias on the collector diode has little influence on the number of electrons that enter the collector. Increasing V_CB does not change the number of free electrons arriving at the collector junction layer.
The symbol of npn and pnp transistors are shown in fig. 5.

Fig. 5

Breakdown Voltages:

Since the two halves of a transistor are diodes, two much reverse voltage on either diode can cause breakdown. The breakdown voltage depends on the width of the depletion layer and the doping levels. Because of the heavy doping level, the emitter diode has a low breakdown voltage approximately 5 to 30 V. The collector diode is less heavily doped so its breakdown voltage is higher around 20 to 300 V. 0http://ecmagic.blogspot.com

noreply@blogger.com (ASIF 007) — Fri, 06 Aug 2010 14:22:00 +0000

Biploar transistor:www.ecmagic.blogspot.com

A transistor is basically a Si on Ge crystal containing three separate regions. It can be either NPN or PNP type fig. 1. The middle region is called the base and the outer two regions are called emitter and the collector. The outer layers although they are of same type but their functions cannot be changed. They have different physical and electrical properties.
In most transistors, emitter is heavily doped. Its job is to emit or inject electrons into the base. These bases are lightly doped and very thin, it passes most of the emitter-injected electrons on to the collector. The doping level of collector is intermediate between the heavy doping of emitter and the light doping of the base.
The collector is so named because it collects electrons from base. The collector is the largest of the three regions; it must dissipate more heat than the emitter or base. The transistor has two junctions. One between emitter and the base and other between the base and the collector. Because of this the transistor is similar to two diodes, one emitter diode and other collector base diode.

Fig .1

When transistor is made, the diffusion of free electrons across the junction produces two depletion layers. For each of these depletion layers, the barrier potential is 0.7 V for Si transistor and 0.3 V for Ge transistor.
The depletion layers do not have the same width, because different regions have different doping levels. The more heavily doped a region is, the greater the concentration of ions near the junction. This means the depletion layer penetrates more deeply into the base and slightly into emitter. Similarly, it penetration more into collector. The thickness of collector depletion layer is large while the base depletion layer is small as shown in fig. 2.

Fig. 2

If both the junctions are forward biased using two d.c sources, as shown in fig. 3a. free electrons (majority carriers) enter the emitter and collector of the transistor, joins at the base and come out of the base. Because both the diodes are forward biased, the emitter and collector currents are large.

Fig. 3a

Fig. 3b

If both the junction are reverse biased as shown in fig. 3b, then small currents flows through both junctions only due to thermally produced minority carriers and surface leakage. Thermally produced carriers are temperature dependent it approximately doubles for every 10 degree celsius rise in ambient temperature. The surface leakage current increases with voltage.

semiconducter diodes

noreply@blogger.com (ASIF 007) — Fri, 30 Jul 2010 15:33:00 +0000

Space charge capacitance C_T of diode:

Reverse bias causes majority carriers to move away from the junction, thereby creating more ions. Hence the thickness of depletion region increases. This region behaves as the dielectric material used for making capacitors. The p-type and n-type conducting on each side of dielectric act as the plate. The incremental capacitance C_T is defined by

Since

Therefore, (E-1)

where, dQ is the increase in charge caused by a change dV in voltage. C_T is not constant, it depends upon applied voltage, there fore it is defined as dQ / dV.

When p-n junction is forward biased, then also a capacitance is defined called diffusion capacitance C_D (rate of change of injected charge with voltage) to take into account the time delay in moving the charges across the junction by the diffusion process. It is considered as a fictitious element that allow us to predict time delay.

If the amount of charge to be moved across the junction is increased, the time delay is greater, it follows that diffusion capacitance varies directly with the magnitude of forward current.

(E-2)

Relationship between Diode Current and Diode Voltage

An exponential relationship exists between the carrier density and applied potential of diode junction as given in equation E-3. This exponential relationship of the current i_D and the voltage v_D holds over a range of at least seven orders of magnitudes of current - that is a factor of 10⁷.

(E-3)

Where,

i_D= Current through the diode (dependent variable in this expression)
v_D= Potential difference across the diode terminals (independent variable in this expression)
I_O= Reverse saturation current (of the order of 10^-15 A for small signal diodes, but I_O is a strong function of temperature)
q = Electron charge: 1.60 x 10^-19 joules/volt
k = Boltzmann's constant: 1.38 x l0^-23 joules /° K
T = Absolute temperature in degrees Kelvin (°K = 273 + temperature in °C)
n = Empirical scaling constant between 0.5 and 2, sometimes referred to as the Exponential Ideality Factor

The empirical constant, n, is a number that can vary according to the voltage and current levels. It depends on electron drift, diffusion, and carrier recombination in the depletion region. Among the quantities affecting the value of n are the diode manufacture, levels of doping and purity of materials. If n=1, the value of k T/ q is 26 mV at 25°C. When n=2, k T/ q becomes 52 mV.

For germanium diodes, n is usually considered to be close to 1. For silicon diodes, n is in the range of 1.3 to 1.6. n is assumed 1 for all junctions all throughout unless otherwise noted.

Equation (E-3) can be simplified by defining V_T =k T/q, yielding

(E-4)

At room temperature (25°C) with forward-bias voltage only the first term in the parentheses is dominant and the current is approximately given by

(E-5)

The current-voltage (l-V) characteristic of the diode, as defined by (E-3) is illustrated in fig. 1. The curve in the figure consists of two exponential curves. However, the exponent values are such that for voltages and currents experienced in practical circuits, the curve sections are close to being straight lines. For voltages less than V_ON, the curve is approximated by a straight line of slope close to zero. Since the slope is the conductance (i.e., i / v), the conductance is very small in this region, and the equivalent resistance is very high. For voltages above V_ON, the curve is approximated by a straight line with a very large slope. The conductance is therefore very large, and the diode has a very small equivalent resistance.

Fig.1 - Diode Voltage relationship

The slope of the curves of fig.1 changes as the current and voltage change since the l-V characteristic follows the exponential relationship of relationship of equation (E-4). Differentiate the equation (E-4) to find the slope at any arbitrary value of v_Dor i_D,

(E-6)

This slope is the equivalent conductance of the diode at the specified values of v_D or i_D.

We can approximate the slope as a linear function of the diode current. To eliminate the exponential function, we substitute equation (E-4) into the exponential of equation (E-7) to obtain

(E-7)

A realistic assumption is that I_O<< i_D equation (E-7) then yields,

(E-8)

The approximation applies if the diode is forward biased. The dynamic resistance is the reciprocal of this expression.

(E-9)

Although r_d is a function of i_d, we can approximate it as a constant if the variation of i_D is small. This corresponds to approximating the exponential function as a straight line within a specific operating range.

Normally, the term R_f to denote diode forward resistance. R_f is composed of r_d and the contact resistance. The contact resistance is a relatively small resistance composed of the resistance of the actual connection to the diode and the resistance of the semiconductor prior to the junction. The reverse-bias resistance is extremely large and is often approximated as infinity.

Temperature Effects:

Temperature plays an important role in determining the characteristic of diodes. As temperature increases, the turn-on voltage, v_ON, decreases. Alternatively, a decrease in temperature results in an increase in v_ON. This is illustrated in fig. 2, where V_ON varies linearly with temperature which is evidenced by the evenly spaced curves for increasing temperature in 25 °C increments.

The temperature relationship is described by equation

V_ON(T_New ) � V_ON(T_room) = k_T(T_New � T _room) (E-10)

Fig. 2 - Dependence of iD on temperature versus vD for real diode (kT = -2.0 mV /°C)

where,

T_room= room temperature, or 25°C.
T_New= new temperature of diode in °C.
V_ON(T_room ) = diode voltage at room temperature.
V_ON (T_New) = diode voltage at new temperature.
k_T = temperature coefficient in V/°C.

Although k_T varies with changing operating parameters, standard engineering practice permits approximation as a constant. Values of k_T for the various types of diodes at room temperature are given as follows:

k_T= -2.5 mV/°C for germanium diodes
k_T = -2.0 mV/°C for silicon diodes

The reverse saturation current, I_O also depends on temperature. At room temperature, it increases approximately 16% per °C for silicon and 10% per °C for germanium diodes. In other words, I_O approximately doubles for every 5 °C increase in temperature for silicon, and for every 7 °C for germanium. The expression for the reverse saturation current as a function of temperature can be approximated as

(E-11)

where K_i= 0.15/°C ( for silicon) and T1 and T2 are two arbitrary temperatures.

semi conductors

noreply@blogger.com (ASIF 007) — Fri, 30 Jul 2010 15:31:00 +0000

The symbol of diode is shown in fig. 4. The terminal connected to p-layer is called anode (A) and the terminal connected to n-layer is called cathode (K)

Fig.4

Reverse Bias:

If positive terminal of dc source is connected to cathode and negative terminal is connected to anode, the diode is called reverse biased as shown in fig. 5.

Fig.5

When the diode is reverse biased then the depletion region width increases, majority carriers move away from the junction and there is no flow of current due to majority carriers but there are thermally produced electron hole pair also. If these electrons and holes are generated in the vicinity of junction then there is a flow of current. The negative voltage applied to the diode will tend to attract the holes thus generated and repel the electrons. At the same time, the positive voltage will attract the electrons towards the battery and repel the holes. This will cause current to flow in the circuit. This current is usually very small (interms of micro amp to nano amp). Since this current is due to minority carriers and these number of minority carriers are fixed at a given temperature therefore, the current is almost constant known as reverse saturation current I_CO.

In actual diode, the current is not almost constant but increases slightly with voltage. This is due to surface leakage current. The surface of diode follows ohmic law (V=IR). The resistance under reverse bias condition is very high 100k to mega ohms. When the reverse voltage is increased, then at certain voltage, then breakdown to diode takes place and it conducts heavily. This is due to avalanche or zener breakdown. The characteristic of the diode is shown in fig. 6.

Fig.6

Forward bias:

When the diode is forward bias, then majority carriers are pushed towards junction, when they collide and recombination takes place. Number of majority carriers are fixed in semiconductor. Therefore as each electron is eliminated at the junction, a new electron must be introduced, this comes from battery. At the same time, one hole must be created in p-layer. This is formed by extracting one electron from p-layer. Therefore, there is a flow of carriers and thus flow of current.

noreply@blogger.com (ASIF 007) — Fri, 30 Jul 2010 15:28:00 +0000

A pure silicon crystal or germanium crystal is known as an intrinsic semiconductor. There are not enough free electrons and holes in an intrinsic semi-conductor to produce a usable current. The electrical action of these can be modified by doping means adding impurity atoms to a crystal to increase either the number of free holes or no of free electrons.

When a crystal has been doped, it is called a extrinsic semi-conductor. They are of two types

• n-type semiconductor having free electrons as majority carriers

• p-type semiconductor having free holes as majority carriers

By themselves, these doped materials are of little use. However, if a junction is made by joining p-type semiconductor to n-type semiconductor a useful device is produced known as diode. It will allow current to flow through it only in one direction. The unidirectional properties of a diode allow current flow when forward biased and disallow current flow when reversed biased. This is called rectification process and therefore it is also called rectifier.

How is it possible that by properly joining two semiconductors each of which, by itself, will freely conduct the current in any direct refuses to allow conduction in one direction.

Consider first the condition of p-type and n-type germanium just prior to joining fig. 1. The majority and minority carriers are in constant motion.

The minority carriers are thermally produced and they exist only for short time after which they recombine and neutralize each other. In the mean time, other minority carriers have been produced and this process goes on and on.

The number of these electron hole pair that exist at any one time depends upon the temperature. The number of majority carriers is however, fixed depending on the number of impurity atoms available. While the electrons and holes are in motion but the atoms are fixed in place and do not move.

Fig.1

As soon as, the junction is formed, the following processes are initiated fig. 2.

Fig.2

Holes from the p-side diffuse into n-side where they recombine with free electrons.
Free electrons from n-side diffuse into p-side where they recombine with free holes.
The diffusion of electrons and holes is due to the fact that large no of electrons are concentrated in one area and large no of holes are concentrated in another area.
When these electrons and holes begin to diffuse across the junction then they collide each other and negative charge in the electrons cancels the positive charge of the hole and both will lose their charges.
The diffusion of holes and electrons is an electric current referred to as a recombination current. The recombination process decay exponentially with both time and distance from the junction. Thus most of the recombination occurs just after the junction is made and very near to junction.
A measure of the rate of recombination is the lifetime defined as the time required for the density of carriers to decrease to 37% to the original concentration

The impurity atoms are fixed in their individual places. The atoms itself is a part of the crystal and so cannot move. When the electrons and hole meet, their individual charge is cancelled and this leaves the originating impurity atoms with a net charge, the atom that produced the electron now lack an electronic and so becomes charged positively, whereas the atoms that produced the hole now lacks a positive charge and becomes negative.

The electrically charged atoms are called ions since they are no longer neutral. These ions produce an electric field as shown in fig. 3. After several collisions occur, the electric field is great enough to repel rest of the majority carriers away of the junction. For example, an electron trying to diffuse from n to p side is repelled by the negative charge of the p-side. Thus diffusion process does not continue indefinitely but continues as long as the field is developed.

Fig.3

This region is produced immediately surrounding the junction that has no majority carriers. The majority carriers have been repelled away from the junction and junction is depleted from carriers. The junction is known as the barrier region or depletion region. The electric field represents a potential difference across the junction also called space charge potential or barrier potential . This potential is 0.7v for Si at 25^o celcious and 0.3v for Ge.

The physical width of the depletion region depends on the doping level. If very heavy doping is used, the depletion region is physically thin because diffusion charge need not travel far across the junction before recombination takes place (short life time). If doping is light, then depletion is more wide (long life time).

HART Communication

noreply@blogger.com (ASIF 007) — Sun, 11 Jul 2010 05:00:00 +0000

For many years, the field communication standard for process automation equipment has been a milliamp (mA) analog current signal. The milliamp current signal varies within a range of 4-2OmA in proportion to the process variable being represented. Li typical applications a signal of 4mA will correspond to the lower limit (0%) of the calibrated range and 2OmA will correspond to the upper limit (100%) of the calibrated range. Virtually all installed systems use this international standard for communicating process variable information between process automation equipment.

HART Field Communications Protocol extends this 4- 2OmA standard to enhance communication with smart field instruments. The HART protocol was designed specifically for use with intelligent measurement and control instruments which traditionally communicate using 4-2OmA analog signals. HART preserves the 4- signal and enables two way digital communications to occur without disturbing the integrity of the 4-2OmA signal. Unlike other digital communication technologies, the HART protocol maintains compatibility with existing 4-2OmA systems, and in doing so, provides users with a uniquely backward compatible solution. HART Communication Protocol is well-established as the existing industry standard for digitally enhanced 4- 2OmA field communication.

THE HART PROTOCOL - AN OVERVIEW

HART is an acronym for "Highway Addressable Remote Transducer". The HART protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-2OmA. This enables two-way field communication to take place and makes it possible for additional information beyond just the normal process variable to be communicated to/from a smart field instrument. The HART protocol communicates at 1200 bps without interrupting the 4-2OmA signal and allows a host application (master) to get two or more digital updates per second from a field device. As the digital FSK signal is phase continuous, there is no interference with the 4- 2OrnA signal.

HART is a master/slave protocol which means that a field (slave) device only speaks when spoken to by a master. The HART protocol can be used in various modes for communicating information to/from smart field in3truments and central control or monitor systems. HART provides for up to two masters (primary and secondary). This allows secondary masters such as handheld communicators to be used without interfering with communications to/from the primary master, i.e. control/monitoring system. The most commonly employed HART communication mode is master/slave communication of digital information simultaneous with transmission of the 4-2OmA signal. The HART protocol permits all digital communication with field devices in either point-to-point or multidrop network configuration. There is an optional "burst" communication mode where single slave device can continuously broadcast a standard HART reply message.

HART COMMUNICATION LAYERS

The HART protocol utilizes the OSI reference model. As is the case for most of the communication systems on the field level, the HART protocol implements only the Layers 1, 2 and 7 of the OSI model. The layers 3 to 6 remain empty since their services are either not required or provided by the application layer 7

IBOC Technology

noreply@blogger.com (ASIF 007) — Sun, 11 Jul 2010 04:58:00 +0000

The engineering world has been working on the development and evaluation of IBOC transmission for some time. The NRSC began evaluation proceedings of general DAB systems in 1995. After the proponents merged into one, Ibiquity was left in the running for potential adoption. In the fall of 2001,the NRSC issued a report on Ibiquity's FM IBOC. This comprehensive report runs 62 pages of engineering material plus 13 appendices. All of the system with its blend-to analog operation as signal levels changes. The application of the FM IBOC has been studied by the NRSC and appears to be understood and accepted by radio engineers.

AM IBOC has recently been studied by an NRSC working group as prelude to its adoption for general broadcast use .Its was presented during the NAB convention in April. The FM report covers eight areas of vital performance concerns to the broadcaster and listener alike .If all of these concerns can be met as successfully by AM IBOC, and the receiver manufactures rally to develop and produce the necessary receiving equipment. The evaluated FM concerns were audio quality, service area, acquisition performance, durability, auxiliary data capacity, and behavior as signal degrades, stereo separation and flexibility.

The FM report paid strong attention to the use of SCA services on FM IBOC. About half of all the operating FM stations employ one or more SCAs for reading for the blind or similar services. Before going to the description of FM IBOC system, it is important to discuss the basic principles of digital radio, and IBOC technology. In the foregoing sections we see the above-mentioned topics

2. BASIC PRINCIPLES OF DIGITAL RADIO

WHAT IS DIGITAL RADIO?

Digital radio is a new method of assembling, broadcasting and receiving communications services using the same digital technology now common in many products and services such as computers, compact discs (CDs) and telecommunications.
Digital radio can:
" Provide for better reception of radio services than current amplitude modulation (AM) and frequency modulation (FM) radio broadcasts;
" Deliver higher quality sound than current AM and FM radio broadcasts to fixed, portable and mobile receivers; and
" Carry ancillary services-in the form of audio, images, data and text-providing
" Program information associated with the station and its audio programs (such as station name, song title, artist's name and record label),
" Other information (e.g. Internet downloads, traffic information, news and weather), and
" Other services (e.g. paging and global satellite positioning).

A fundamental difference between analog and digital broadcasting is that digital technology involves the delivery of digital bit streams that can be used not only for sound broadcasting but all manner of multimedia services.

Adaptive Optics in Ground Based Telescopes

noreply@blogger.com (ASIF 007) — Sun, 11 Jul 2010 04:53:00 +0000

Adaptive optics is a new technology which is being used now a days in ground based telescopes to remove atmospheric tremor and thus provide a clearer and brighter view of stars seen through ground based telescopes. Without using this system, the images obtained through telescopes on earth are seen to be blurred, which is caused by the turbulent mixing of air at different temperatures.

Adaptive optics in effect removes this atmospheric tremor. It brings together the latest in computers, material science, electronic detectors, and digital control in a system that warps and bends a mirror in a telescope to counteract, in real time the atmospheric distortion.

The advance promises to let ground based telescopes reach their fundamental limits of resolution and sensitivity, out performing space based telescopes and ushering in a new era in optical astronomy. Finally, with this technology, it will be possible to see gas-giant type planets in nearby solar systems in our Milky Way galaxy. Although about 100 such planets have been discovered in recent years, all were detected through indirect means, such as the gravitational effects on their parent stars, and none has actually been detected directly.

WHAT IS ADAPTIVE OPTICS ?

Adaptive optics refers to optical systems which adapt to compensate for optical effects introduced by the medium between the object and its image. In theory a telescope's resolving power is directly proportional to the diameter of its primary light gathering lens or mirror. But in practice , images from large telescopes are blurred to a resolution no better than would be seen through a 20 cm aperture with no atmospheric blurring. At scientifically important infrared wavelengths, atmospheric turbulence degrades resolution by at least a factor of 10.

Space telescopes avoid problems with the atmosphere, but they are enormously expensive and the limit on aperture size of telescopes is quite restrictive. The Hubble Space telescope, the world's largest telescope in orbit , has an aperture of only 2.4 metres, while terrestrial telescopes can have a diameter four times that size.

In order to avoid atmospheric aberration, one can turn to larger telescopes on the ground, which have been equipped with ADAPTIVE OPTICS system. With this setup, the image quality that can be recovered is close to that the telescope would deliver if it were in space. Images obtained from the adaptive optics system on the 6.5 m diameter telescope, called the MMT telescope illustrate the impact.

A 64 Point Fourier Transform Chip

noreply@blogger.com (ASIF 007) — Sun, 11 Jul 2010 04:52:00 +0000

Fourth generation wireless and mobile system are currently the focus of research and development. Broadband wireless system based on orthogonal frequency division multiplexing will allow packet based high data rate communication suitable for video transmission and mobile internet application. Considering this fact we proposed a data path architecture using dedicated hardwire for the baseband processor. The most computationally intensive part of such a high data rate system are the 64-point inverse FFT in the transmit direction and the viterbi decoder in the receiver direction. Accordingly an appropriate design methodology for constructing them has to be chosen a) how much silicon area is needed b) how easily the particular architecture can be made flat for implementation in VLSI c) in actual implementation how many wire crossings and how many long wires carrying signals to remote parts of the design are necessary d) how small the power consumption can be .This paper describes a novel 64-point FFT/IFFT processor which has been developed as part of a large research project to develop a single chip wireless modem.

ALGORITHM FORMULATION

The discrete fourier transformation A(r) of a complex data sequence B(k) of length N
where r, k ={0,1……, N-1} can be described as

Where WN = e-2?j/N . Let us consider that N=MT , ? = s+ Tt and k=l+Mm,where s,l ? {0,1…..7} and m, t ? {0,1,….T-1}. Applying these values in first equation and we get

This shows that it is possible to realize the FFT of length N by first decomposing it to one M and one T-point FFT where N = MT, and combinig them. But this results in in a two dimensional instead of one dimensional structure of FFT. We can formulate 64-point by considering M =T = 8

This shows that it is possible to express the 64-point FFT in terms of a two dimensional structure of 8-point FFTs plus 64 complex inter-dimensional constant multiplications. At first, appropriate data samples undergo an 8-point FFT computation. However, the number of non-trivial multiplications required for each set of 8-point FFT gets multiplied with 1. Eight such computations are needed to generate a full set of 64 intermediate data, which once again undergo a second 8-point FFT operation . Like first 8-point FFT for second 8-point again such computions are required. Proper reshuffling of the data coming out from the second 8-point FFT generates the final output of the 64-point FFT .

Fig. Signal flow graph of an 8-point DIT FFT.

For realization of 8-point FFT using the conventional DIT does not need to use any multiplication operation.

The constants to be multiplied for the first two columns of the 8-point FFT structure are either 1 or j . In the third column, the multiplications of the constants are actually addition/subtraction operation followed multiplication of 1/?2 which can be easily realized by using only a hardwired shift-and-add operation. Thus an 8-point FFT can be carried out without using any true digital multiplier and thus provide a way to realize a low- power 64-point FFT at reduced hardware cost. Since a basic 8-point FFT does not need a true multiplier. On the other hand, the number of non-trivial complex multiplications for the conventional 64-point radix-2 DIT FFT is 66. Thus the present approach results in a reduction of about 26% for complex multiplication compared to that required in the conventional radix-2 64-point FFT. This reduction of arithmetic complexity furthur enhances the scope for realizing a low-power 64-point FFT processor. However, the arithmetic complexity of the proposed scheme is almost the same to that of radix-4 FFT algorithm since the radix-4 64-point FFT algorithm needs 52 non-trivial complex multiplications.

Chip Morphing

noreply@blogger.com (ASIF 007) — Sun, 11 Jul 2010 04:49:00 +0000

1.1. The Energy Performance Tradeoff

Engineering is a study of tradeoffs. In computer engineering the tradeoff has traditionally been between performance, measured in instructions per second, and price. Because of fabrication technology, price is closely related to chip size and transistor count. With the emergence of embedded systems, a new tradeoff has become the focus of design. This new tradeoff is between performance and power or energy consumption. The computational requirements of early embedded systems were generally more modest, and so the performance-power tradeoff tended to be weighted towards power. "High performance" and "energy efficient" were generally opposing concepts.

However, new classes of embedded applications are emerging which not only have significant energy constraints, but also require considerable computational resources. Devices such as space rovers, cell phones, automotive control systems, and portable consumer electronics all require or can benefit from high-performance processors. The future generations of such devices should continue this trend.

Processors for these devices must be able to deliver high performance with low energy dissipation. Additionally, these devices evidence large fluctuations in their performance requirements. Often a device will have very low performance demands for the bulk of its operation, but will experience periodic or asynchronous "spikes" when high-performance is needed to meet a deadline or handle some interrupt event. These devices not only require a fundamental improvement in the performance power tradeoff, but also necessitate a processor which can dynamically adjust its performance and power characteristics to provide the tradeoff which best fits the system requirements at that time.

1.2. Fast, Powerful but Cheap, and Lots of Control

These motivations point to three major objectives for a power conscious embedded processor. Such a processor must be capable of high performance, must consume low amounts of power, and must be able to adapt to changing performance and power requirements at runtime.

The objective of this seminar is to define a micro-architecture which can exhibit low power consumption without sacrificing high performance. This will require a fundamental shift to the power-performance curve presented by traditional microprocessors. Additionally, the processor design must be flexible and reconfigurable at run-time so that it may present a series of configurations corresponding to different tradeoffs between performance and power consumption.

1.3. MORPH

These objectives and motivations were identified during the MORPH project, a part of the Power Aware Computing / Communication (PACC) initiative. In addition to exploring several mechanisms to fundamentally improve performance, the MORPH project brought forth the idea of "gear shifting" as an analogy for run-time reconfiguration. Realizing that real world applications vary their performance requirements dramatically over time, a major goal of the project was to design microarchitectures which could adjust to provide the minimal required performance at the lowest energy cost. The MORPH project explored a number of microarchitectural techniques to achieve this goal, such as morphable cache hierarchies and exploiting bit-slice inactivity. One technique, multi-cluster architectures, is the direct predecessor of this work. In addition to microarchitectural changes, MORPH also conducted a survey of realistic embedded applications which may be power constrained. Also, design implications of a power aware runtime system were explored.

How to study electronics

noreply@blogger.com (ASIF 007) — Thu, 08 Jul 2010 01:51:00 +0000

Education and training

Electronics engineers typically possess an academic degree with a major in electronic engineering. The length of study for such a degree is usually three or four years and the completed degree may be designated as a Bachelor of Engineering, Bachelor of Science, Bachelor of Applied Science, or Bachelor of Technology depending upon the university. Many UK universities also offer Master of Engineering (MEng) degrees at undergraduate level.

The degree generally includes units covering physics, chemistry, mathematics, project management and specific topics in electrical engineering. Initially such topics cover most, if not all, of the subfields of electronic engineering. Students then choose to specialize in one or more subfields towards the end of the degree.

Some electronics engineers also choose to pursue a postgraduate degree such as a Master of Science (MSc), Doctor of Philosophy in Engineering (PhD), or an Engineering Doctorate (EngD). The Master degree is being introduced in some European and American Universities as a first degree and the differentiation of an engineer with graduate and postgraduate studies is often difficult. In these cases, experience is taken into account. The Master's degree may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy consists of a significant research component and is often viewed as the entry point to academia.

In most countries, a Bachelor's degree in engineering represents the first step towards certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa), Chartered Engineer or Incorporated Engineer (in the United Kingdom, Ireland, India and Zimbabwe), Chartered Professional Engineer (in Australia) or European Engineer (in much of the European Union).

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electronic systems. Although most electronic engineers will understand basic circuit theory, the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI but are largely irrelevant to engineers working with macroscopic electrical systems.

Early electronics

noreply@blogger.com (ASIF 007) — Thu, 08 Jul 2010 01:37:00 +0000

In 1893, Nikola Tesla made the first public demonstration of radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of radio communication.^[13] In 1896, Guglielmo Marconi went on to develop a practical and widely used radio system.^[14]^[15]^[16] In 1904, John Ambrose Fleming, the first professor of electrical Engineering at University College London, invented the first radio tube, the diode. One year later, in 1906, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.

Electronics is often considered to have begun when Lee De Forest invented the vacuum tube in 1907. Within 10 years, his device was used in radio transmitters and receivers as well as systems for long distance telephone calls. In 1912, Edwin H. Armstrong invented the regenerative feedback amplifier and oscillator; he also invented the superheterodyne radio receiver and could be considered the father of modern radio.^[17] Vacuum tubes remained the preferred amplifying device for 40 years, until researchers working for William Shockley at Bell Labs invented the transistor in 1947. In the following years, transistors made small portable radios, or transistor radios, possible as well as allowing more powerful mainframe computers to be built. Transistors were smaller and required lower voltages than vacuum tubes to work. In the interwar years the subject of electronics was dominated by the worldwide interest in radio and to some extent telephone and telegraph communications. The terms 'wireless' and 'radio' were then used to refer to anything electronic. There were indeed few non-military applications of electronics beyond radio at that time until the advent of television. The subject was not even offered as a separate university degree subject until about 1960.^[18]

Prior to World War II, the subject was commonly known as 'radio engineering' and basically was restricted to aspects of communications and RADAR, commercial radio and early television. At this time, study of radio engineering at universities could only be undertaken as part of a physics degree. Later, in post war years, as consumer devices began to be developed, the field broadened to include modern TV, audio systems, Hi-Fi and latterly computers and microprocessors. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronic engineering, which then became a stand alone university degree subject, usually taught alongside electrical engineering with which it had become associated due to some similarities.

Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by hand. These non-integrated circuits consumed much space and power, were prone to failure and were limited in speed although they are still common in simple applications. By contrast, integrated circuits packed a large number — often millions — of tiny electrical components, mainly transistors, into a small chip around the size of a coin.^[19]

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 16:47:00 +0000

Basic knowledge
of Electronic parts

I will explain the components to use for the electronic circuits on these pages.

Resistors	Coils
Capacitors	Printed Wiring Boards
Diodes	Relays
Transistors	Wiring materials
Integrated Circuits

Integrated Circuits

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 16:42:00 +0000

An integrated circuit contains transistors, capacitors, resistors and other parts packed in high density on one chip.
Although the function is similar to a circuit made with separate components, the internal structure of the components are different in an integrated circuit.
The transistors, resistors, and capacitors are formed very small, and in high density on a foundation of silicon. They are formed by a variation of printing technology.
There are many kind of ICs, including special use ICs.

The top left device in the photograph is an SN7400. It contains 4 separate "2 input NAND" circuits. There are 7 pins on each side, 14 pins total.
ICs in this form are called Dual In line Package (DIP).
When an IC has only one row of pins, it os called a Single In line Package (SIP).
The number of pins changes depending on the function of IC.

At the bottom left is an IC socket for use with 14 pin DIP ICs.
ICs can be attached directly to the printed circuit board with solder, but it's better to use an IC socket, because you can easily exchange it should the IC fail.

On the top right is an LM386N audio amplifier. It can be used for amplification of low frequency, low power signals. IT has 8 pins and the maximum output is 660mW.

On the bottom right is a TA7368P, which also is for amplification of low frequency electric power. It has a maximum output of 1.1 watts.
It is a 9 pin SIP IC.

Common ICs

Below, the most common ICs are shown. (Those parts that I use most.)
For extensive details on each part, see the corresponding data sheet.
The part numbers of the SN74 series ICs are written with a 74, often followed by LS or HC.
LS (Low power Shottky) indicates low power consumption. HC indicates the device is High speed C-MOS (Complementary-Metal Oxide Semiconductor), and is also a low power consumption IC.
The average current consumption for each type of chip is listed below.
The current shown is for when the device is in a LOW state output. In the case of the LOW state output, current consumption is much greater than in the HIGH state output.

SN7400	-----	22mA
SN74LS00	-----	4.4mA
SN74HC00	-----	0.02mA

Several kinds of ICs are not available in the LS or HC type. For example, SN7445 is not available in LS or HC. It is available only as SN7445, the normal type.

Name	Function	Vcc	Remarks
SN74HC00	Quad 2 Input NAND	+5V	2 input NAND circuits entered 4 pieces
SN74HC04	Hex Inverters	+5V	Inverter circuit entered 6 pieces Details
SN74LS42	BCD to DECIMAL Decoder	+5V	One of output takes LOW state serected by the binary input.
SN7445	O.C. BDC to DECIMAL Decoder/Driver	+5V	Open collector type of 7442 Max current of output is 80mA.
SN74LS47	BCD to Segment Decoder/Driver	+5V	Front View Driving IC of ‚Vsegments LED. Open collector type Max resistance voltage:15V 6 and 9 disply type: Related 74247
SN74HC73	Dual JK-FFs With Clear	+5V	2 pieces of JK-FF
SN74LS90	Decade Counter	+5V	Asynchronous 2 + 5 counter. Async preset : 9 Async clear Related 74290 74390
SN74HC93	4-Bit Binary Counter	+5V	Asynchronous 2 + 8 counter.
SN74HC123	Dual Retriggaerable Single Shot	+5V	Single shot resister holds the output in the required time from the input states goes to ON. The output holding time corresponds to C(capacitor) and R(resistor) connected to the Cext(External capacitor) and Rext(External resistor) respectivly.
SN74LS247	BCD to Segment Decoder/Driver	+5V	Front View 6 and 9 disply type: Related 7447
SN74LS290	Decade Counter	+5V	This type is the same as the SN7490, with a different layout of pins. Related 7490 74390
SN74HC390	Dual Decade Counters	+5V	Type that inserted 2 SN7490. Presetting 9 is omitted . Related 7490 74290
4040B	12Bit Binary Counter (CMOS)	+5V	12-stage Binary counter. It has a clear function. Counts downward with an external clock pulse.
4541B	Progarammable Oscillator/Timer (CMOS)	+5V	Programmable 16 stage binary counter. Used in RC oscillation circuits, power reset, output control circuits. Tap outputs of 8, 10, 13, 16 bits are possible by the control terminal.
NE555	Timer	+4.5 to +16V	Max frequency: 500kHz Temperature drift: 0.005%/°C. Max output current: 200mA. Delay time setting :several micro sec to several hours
LM386N-1	Low frequency electric power amplifier	+4 to 12V	Max output: 660mW Load: 8 to 32-ohm Waiting current: 4mA
LM386N-4	Low frequency electric power amplifier	+5 to 18V	Max output: 1.25W Load: 8 to 32-ohm Waiting current: 4mA
TA7368P	Low frequency electric power amplifier	+2 to +10V	Max output: 1.1W Load: 4 to 16-ohm
uPC319	Voltage comparator	5 to 18V ±5 to ±18V	Standard general use comparator with single power supply/dual power supply operation Other compatible ICs LM319 NJM319 AN1319
7975	Multi-melody IC (CMOS)	+1.5 to +3V	Melody IC that includes 8 pre-programmed melodies. It has 2 sound resources and a settable envelope. Title Green-Sleeves Fur Elise Heavenly Creatures Ich bin ein musikante Valse Favorite Holderia Amaryllis Home On The Range

Three Terminal Voltage Regulator

It is very easy to get stabilized voltage for ICs by using a three terminal voltage regulator.
The power supply voltage for a car is +12V - +14V. At this voltage, some ICs can not operate directly except for the car component ICs. In this case, a three terminal voltage regulator is necessary to get the required voltage.
The three terminal voltage regulator outputs stabilized voltage at a lower level than the higher input voltage. A voltage regulator cannot put out higher voltage than the input voltage. They are similar in appearance to a transistor.

On the left in the photograph is a 78L05. The size and form is similar to a 2SC1815 transistor.
The output voltage is +5V, and the maximum output current is about 100mA.
The maximum input voltage is +35V. (Differs by manufacturer.)

On the right is a 7805. The output voltage is +5V, and maximum output current is 500mA to 1A. (It depends on the heat sink used)
The maximum input voltage is also +35V.

There are many types with different output voltages.
5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V

Component Lead of Three Terminal Voltage Regulator

Because the component leads differ between kinds of regulators,
you need to confirm the leads with a datasheet, etc.

Example of 78L05

Part number is printed on the flat face of the regulator, and indicates the front.

Right side :

Input

Center :

Ground

Left side :

Output

Example of 7805
Part number is printed on the flat face of the regulator, and indicates the front.

Right side : Output
Center : Ground
Left side : Input

Opposite from 78L05.

Wiring materials

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 16:40:00 +0000

Wire is used to electrically connect circuit parts, devices, equipment etc.
There are various kinds of wiring materials. On this page, I introduce the type that is used for the assembly of electronic circuits.

The different types of wire can be divided largely into two categories: single wire and twisted strand wire. It really doesn't matter which kind you use for a given application, but usually, single wire is used to connect devices (resistors, capacitors ect) together on the PWB. (Parts that don't move)
It is also used for jumper wiring.
Twisted strand wire can bend freely, so it can be used for wiring on the PWB, and also to connect discrete pieces of equipment.
If single wire is used to connnect separate equipment, it will break soon, as it is not very flexible.

It is convenient to use the single tin coated wire of the diameter 0.32 mm for the wiring of PWB. If the diameter is larger, soldering becomes a little bit difficult. And if the diameter is too thin, it becomes difficult to bend the wire the way you want it to stay.
It's best to use whatever wire you are comfortable with, and not worry about those things.

If you want to connect separated parts on the PWB, twisted wire covered with soft insulation material is most convenient for wiring.
It's convenient to wire the circuit using different color wires for different purposes. Otherwise, wiring the circuit with many wires the same color gets confusing.

The photograph on the left shows several colors of twisted wire.
It is called 0.12/7PVC.
The pictured wire is comprised of 7 tin coated wires 0.12 mm each in diameter, covered by very thin PVC plastic.

In the photograph to the right is pictured tin coated wire with a diameter of 0.32 mm.
It is convenient to use for wiring components, jumper wiring etc. when you are building a circuit on a universal PWB.
Pictured at the left is polyurethane wire, 0.4 mm in diameter.
It is used for making coils.
There are several kinds of coated wires. Tin coated wire colored silver, polyurethane enameled copper wire(UEW) which has a thin brown color, polyester enameled copper wire (PEW) which is also thin brown, and enameled wire with a burnt brown color.
Coated wire is used for making coil components like a transformers.

The PEW can not be soldered, because the polyester coating will not melt at the soldering temperature. So if you want to solder PEW wire, you need to scrape the enamel off the wire.
In case of the UEW, you do not need to scrape the insulation off the wire, because the polyurethane will melt at the soldering temperature.

In this photograph is a tool used for wiring.
Copper wire can be drawn out from the tip like the core of a pencil.
First, the wire is attached and solderd to the first lead of a given component.
Next, the wire is drawn out from the tool and can be soldered at the desired lead of another component.
The wire is polyurethane coated single wire of 0.2 mm thickness.

Transistors

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 16:38:00 +0000

The transistor's finction is to amplify an electric current.
Many different kinds of transistors are used in analog circuits, for different reasons. This is not the case for digital circuits. In a digital circuit, only two values matter; on or off. The amplification abilitiy of a transistor is not relevant in a digital circuit. In many cases, a circuit is built with integrated circuits(ICs).
Transistors are often used in digital circuits as buffers to protect ICs. For example, when powering an electromagnetic switch (called a 'relay'), or when controlling a light emitting diode. (In my case.)

Two different symbols are used for the transistor.

PNP type and NPN type

The name (standard part number) of the transistor, as well as the type and the way it is used is shown below.

2SAXXXX PNP type high frequency

2SBXXXX PNP type low frequency

2SCXXXX NPN type high frequency

2SDXXXX NPN type low frequency

The direction of the current flow differs between the PNP and NPN type.
When the power supply is the side of the positive (plus), the NPN type is easy to use.

Appearance of the Transistor

The outward appearance of the transistor varies. Here, two kinds are shown.

On the left in the photograph is a 2SC1815 transistor, which is good for use in a digital circuit. They are inexpensive when I buy them in quantity. In Japan it costs 2,000 yen for a pack of 200 pieces. (About 10 US cents/piece in 1998)

On the right is a device which is used when a large current is to be handled. Its part number is 2SD880.

The electrical characteristics of each is as follows.

Item	2SC1815	2SD880
V_CEO(V)	50	60
I_C(mA)	150	3A
P_C(mW)	400	30W
h_FE	70 - 700	60 - 300
f_T(MHz)	80	3

V_CEO	:	The maximum voltage that can be handled across the collector(C) and emitter(E) when the base(B) is open. (Not connected) (It may be shown as V_CE)
I_C	:	The maximum collector(C) current.
P_C	:	Maximum collector(C) loss that continuously can cause it consumed at surroundings temperature (Ta)=25°C (no radiator)
h_FE	:	The current gain to DC at the emitter(E). (I_C/I_B)
f_T	:	The maximum DC switching frequency. (the transision frequency)

Data sheet for 2SC1815

Component Lead of the Transistor

Because the component leads differ between kinds of transistors,
you need to confirm the leads with a datasheet, etc.

Example of 2SC1815 transistor
Part number is printed on the flat face of the transistor, and indicates the front.

Right side : Base
Center : Collector
Left side : Emitter

Example of 2SD880 transistor
Part number is printed on the flat face of the transistor, and indicates the front.

Right side : Emitter
Center : Collector
Left side : Base

2SC1815 is opposite.

Relays

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 16:35:00 +0000

The relay takes advantage of the fact that when electricity flows through a coil, it becomes an electromagnet.
The electromagnetic coil attracts a steel plate, which is attached to a switch. So the switch's motion (ON and OFF) is controled by the current flowing to the coil, or not, respectively.

A very useful feature of a relay is that it can be used to electrically isolate different parts of a circuit.
It will allow a low voltage circuit (e.g. 5VDC) to switch the power in a high voltage circuit (e.g. 100 VAC or more).

The relay operates mechanically, so it can not operate at high speed.

There are many kind of relays. You can select one according to your needs.
The various things to consider when selecting a relay are its size, voltage and current capacity of the contact points, drive voltage, impedance, number of contacts, resistance of the contacts, etc.
The resistance voltage of the contacts is the maximum voltage that can be conducted at the point of contact in the switch. When the maximum is exceeded, the contacts will spark and melt, sometimes fusing together. The relay will fail. The value is printed on the relay.

On the left in the photograph is a small relay with a coil driving voltage of 12 VDC. It has two electrically independant points of contact (switches.)
Although the resistance and permissible voltage and current at the point of contact are indistinct, I think that it will handle several hundred mA.

The relay on the right in the photograph can be used to control a 100 VAC system. Its driving voltage is 3 VDC, and if it is used to control an AC system, the maximum resistance voltage is 125 VAC, and the permissible current limit is 1A. If it is used to control a DC system, the maximum resistance voltage is DC30V, and the permissible current limit is 2A. It has one contact only.

Both types of relay can be mounted on the PWB; the spacing of the component leads is a multiple of 0.1 inches. It can also be mounted on the universal PWB.

The physical dimensions of the relay on the left are width 19.5 mm, height 10 mm, and depth 10 mm.
The one that is on the right has the width 20 mm, height 15 mm, and depth 11 mm.

The relay pictured to the right is able to handle a little larger electric power.
Its driving voltage is 12 VDC, maximum resistance voltage is AC 240V, and the permissible current limit is 5A in case of AC system. In a DC system, the maximum resistance voltage is DC 28V, and the permissible current limit is 5A. It has 2 contacts.

This type of relay can not be mounted on the PWB. It needs a socket, and mounts on the case or some other place with a screw.

The dimensions are width 22 mm, height 35 mm, and depth 20 mm.

Diodes

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 15:41:00 +0000

A diode is a semiconductor device which allows current to flow through it in only one direction. Although a transistor is also a semiconductor device, it does not operate the way a diode does. A diode is specifically made to allow current to flow through it in only one direction.
Some ways in which the diode can be used are listed here.
A diode can be used as a rectifier that converts AC (Alternating Current) to DC (Direct Current) for a power supply device.
Diodes can be used to separate the signal from radio frequencies.
Diodes can be used as an on/off switch that controls current.
This symbol is used to indicate a diode in a circuit diagram.

The meaning of the symbol is (Anode)(Cathode).
Current flows from the anode side to the cathode side.

Although all diodes operate with the same general principle, there are different types suited to different applications. For example, the following devices are best used for the applications noted.

	Voltage regulation diode (Zener Diode) The circuit symbol is . It is used to regulate voltage, by taking advantage of the fact that Zener diodes tend to stabilize at a certain voltage when that voltage is applied in the opposite direction.
	Light emitting diode The circuit symbol is . This type of diode emits light when current flows through it in the forward direction. (Forward biased.)
	Variable capacitance diode The circuit symbol is . The current does not flow when applying the voltage of the opposite direction to the diode. In this condition, the diode has a capacitance like the capacitor. It is a very small capacitance. The capacitance of the diode changes when changing voltage. With the change of this capacitance, the frequency of the oscillator can be changed.

The graph on the right shows the electrical characteristics of a typical diode.

When a small voltage is applied to the diode in the forward direction, current flows easily.
Because the diode has a certain amount of resistance, the voltage will drop slightly as current flows through the diode. A typical diode causes a voltage drop of about 0.6 - 1V (V_F) (In the case of silicon diode, almost 0.6V)
This voltage drop needs to be taken into consideration in a circuit which uses many diodes in series. Also, the amount of current passing through the diodes must be considered.

When voltage is applied in the reverse direction through a diode, the diode will have a great resistance to current flow.
Different diodes have different characteristics when reverse-biased. A given diode should be selected depending on how it will be used in the circuit.
The current that will flow through a diode biased in the reverse direction will vary from several mA to just µA, which is very small.

The limiting voltages and currents permissible must be considered on a case by case basis. For example, when using diodes for rectification, part of the time they will be required to withstand a reverse voltage. If the diodes are not chosen carefully, they will break down.

Rectification / Switching / Regulation Diode

The stripe stamped on one end of the diode shows indicates the polarity of the diode.
The stripe shows the cathode side.
The top two devices shown in the picture are diodes used for rectification. They are made to handle relatively high currents. The device on top can handle as high as 6A, and the one below it can safely handle up to 1A.
However, it is best used at about 70% of its rating because this current value is a maximum rating.
The third device from the top (red color) has a part number of 1S1588. This diode is used for switching, because it can switch on and off at very high speed. However, the maximum current it can handle is 120 mA. This makes it well suited to use within digital circuits. The maximum reverse voltage (reverse bias) this diode can handle is 30V.
The device at the bottom of the picture is a voltage regulation diode with a rating of 6V. When this type of diode is reverse biased, it will resist changes in voltage. If the input voltage is increased, the output voltage will not change. (Or any change will be an insignificant amount.) While the output voltage does not increase with an increase in input voltage, the output current will.
This requires some thought for a protection circuit so that too much current does not flow.
The rated current limit for the device is 30 mA.
Generally, a 3-terminal voltage regulator is used for the stabilization of a power supply. Therefore, this diode is typically used to protect the circuit from momentary voltage spikes. 3 terminal regulators use voltage regulation diodes inside.

Diode bridge

Rectification diodes are used to make DC from AC. It is possible to do only 'half wave rectification' using 1 diode. When 4 diodes are combined, 'full wave rectification' occurrs.
Devices that combine 4 diodes in one package are called diode bridges. They are used for full-wave rectification.

The photograph on the left shows two examples of diode bridges.

The cylindrical device on the right in the photograph has a current limit of 1A. Physically, it is 7 mm high, and 10 mm in diameter.
The flat device on the left has a current limit of 4A. It is has a thickness of 6 mm, is 16 mm in height, and 19 mm in width.

The photograph on the right shows a large, high-power diode bridge.
It has a current capacity of 15A. The peak reverse-bias voltage is 400V.
Diode bridges with large current capacities like this one, require a heat sink. Typically, they are screwed to a piece of metal, or the chasis of device in which they are used. The heat sink allows the device to radiate excess heat.
As for size, this one is 26 mm wide on each side, and the height of the module part is 10 mm.

Light Emitting Diode ( LED )

Light emitting diodes must be choosen according to how they will be used, because there are various kinds.
The diodes are available in several colors. The most common colors are red and green, but there are even blue ones.

The device on the far right in the photograph combines a red LED and green LED in one package. The component lead in the middle is common to both LEDs. As for the remaing two leads, one side is for the green, the other for the red LED. When both are turned on simultaneously, it becomes orange.

When an LED is new out of the package, the polarity of the device can be determined by looking at the leads. The longer lead is the Anode side, and the short one is the Cathode side.

The polarity of an LED can also be determined using a resistance meter, or even a 1.5 V battery.

When using a test meter to determine polarity, set the meter to a low resistance measurement range. Connect the probes of the meter to the LED. If the polarity is correct, the LED will glow. If the LED does not glow, switch the meter probes to the opposite leads on the LED. In either case, the side of the diode which is connected to the black meter probe when the LED glows, is the Anode side. Positive voltage flows out of the black probe when the meter is set to measure resistance.

It is possible to use an LED to obtain a fixed voltage.
The voltage drop (forward voltage, or V_F) of an LED is comparatively stable at just about 2V.

I explain a circuit in which the voltage was stabilized with an LED in "Thermometer of bending apparatus-2".

Shottky barrier diode

Diodes are used to rectify alternating current into direct current. However, rectification will not occur when the frequency of the alternating current is too high. This is due to what is known as the "reverse recovery characteristic."
The reverse recovery characteristic can be explained as follows:
IF the opposite voltage is suddenly applied to a forward-biased diode, current will continue to flow in the forward direction for a brief moment. This time until the current stops flowing is called the Reverse Recovery Time. The current is considered to be stopped when it falls to about 10% of the value of the peak reverse current.
The Shottky barrier diode has a short reverse recovery time, which makes it ideally suited to use in high frequency rectification.

The shottky barrier diode has the following characteristics.

The voltage drop in the forward direction is low.

The reverse recovery time is short.

However, it has the following disadvantages.

The diode can have relatively high leakage current.

The surge resistance is low.

Because the reverse recovery time is short, this diode is often used for the switching regulator in a high frequency circuit.

Printed Wiring Boards

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 15:39:00 +0000

When assembling an electronic circuit, a board is needed on which the components can be mounted and wired together. This board is called a Printed Wiring Board (PWB).
In Japan, the printed wiring board used to be called a "Printed Circuit Board." Nowadays in Japan the name "Printed Circuit Board" is not used because the initials of "Printed Circuit Board" are "PCB." PCB also stands for "Polychlorinated Biphenyls (PCBs)," which is a poison. So in Japan, we refer to the boards as "Printed Wiring Boards." In other countries, they are still refered to as "Printed Circuit Boards," or PCBs.

Making a PWB takes a lot of work, and can be very difficult. For this reason, for many hand-made circuits, I often use a universal PWB.
The universal PWB consists of an insulation board drilled with .8mm holes at 0.1 inch (2.54 mm) intervals. The board is completely covered with these holes from edge to edge. The insulation board is comprised of fiberglass (glass epoxy), paper epoxy, or bakelite plastic.
Centered around each hole on the bottom of the PWB is an (approximately) 2mm copper leaf (known as the "land" or "pad").

To use the board, the parts are mounted on the face of the board, and the component leads are passed through the nearest holes, to project through the bottom of the board, where the wires can be soldered together.
The interval between the holes is 0.1 inches (2.54 mm), so DIP or SIP ICs can be easily mounted.

The photograph shows a PWB made of glass epoxy. The color is green.
Paper epoxy boards have a beige color. In case of bakelite, the color is thin brown.

As for the size of the board, there are several kinds by the number of the holes.
From the left side in the photograph
55 x 40 holes (size 160 x 115 mm)
30 x 25 holes (size 95 x 72 mm)
25 x 15 holes (size 72 x 47 mm)

There are various sizes in addition to what I have shown, so you can select a board according to your needs.
The boards can also be cut to size.

On the top right in the photograph, the back side is shown. The copper leaf on this board has been pre-soldered ("tinned") to make soldering easier, so it has a silver color. If the board has not been pre-soldered, then it is seen to have a copper color.

Capacitors

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 15:31:00 +0000

The capacitor's function is to store electricity, or electrical energy.
The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).
This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only for a moment. You can confirm that the meter's needle moves off of zero, but returns to zero right away.
When you connect the meter's probes to the capacitor in reverse, you will note that current once again flows for a moment. Once again, when the capacitor has fully charged, the current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A "DC cut" filter.)
However, in the case of alternating current, the current will be allowed to pass. Alternating current is similar to repeatedly switching the test meter's probes back and forth on the capacitor. Current flows every time the probes are switched.

The value of a capacitor (the capacitance), is designated in units called the Farad ( F ).
The capacitance of a capacitor is generally very small, so units such as the microfarad ( 10^-6F ), nanofarad ( 10^-9F ), and picofarad (10^-12F ) are used.
Recently, an new capacitor with very high capacitance has been developed. The Electric Double Layer capacitor has capacitance designated in Farad units. These are known as "Super Capacitors."

Sometimes, a three-digit code is used to indicate the value of a capacitor. There are two ways in which the capacitance can be written. One uses letters and numbers, the other uses only numbers. In either case, there are only three characters used. [10n] and [103] denote the same value of capacitance. The method used differs depending on the capacitor supplier. In the case that the value is displayed with the three-digit code, the 1st and 2nd digits from the left show the 1st figure and the 2nd figure, and the 3rd digit is a multiplier which determines how many zeros are to be added to the capacitance. Picofarad ( pF ) units are written this way.
For example, when the code is [103], it indicates 10 x 10³, or 10,000pF = 10 nanofarad( nF ) = 0.01 microfarad( µF ).
If the code happened to be [224], it would be 22 x 10⁴ = or 220,000pF = 220nF = 0.22µF.
Values under 100pF are displayed with 2 digits only. For example, 47 would be 47pF.

The capacitor has an insulator( the dielectric ) between 2 sheets of electrodes. Different kinds of capacitors use different materials for the dielectric.

Breakdown voltage
When using a capacitor, you must pay attention to the maximum voltage which can be used. This is the "breakdown voltage." The breakdown voltage depends on the kind of capacitor being used. You must be especially careful with electrolytic capacitors because the breakdown voltage is comparatively low. The breakdown voltage of electrolytic capacitors is displayed as Working Voltage.
The breakdown voltage is the voltage that when exceeded will cause the dielectric (insulator) inside the capacitor to break down and conduct. When this happens, the failure can be catastrophic.

I will introduce the different types of capacitors below.

Electrolytic Capacitors (Electrochemical type capacitors)

Aluminum is used for the electrodes by using a thin oxidization membrane.
Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin.
The most important characteristic of electrolytic capacitors is that they have polarity. They have a positive and a negative electrode.[Polarised] This means that it is very important which way round they are connected. If the capacitor is subjected to voltage exceeding its working voltage, or if it is connected with incorrect polarity, it may burst. It is extremely dangerous, because it can quite literally explode. Make absolutely no mistakes.
Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.
Electrolytic capacitors range in value from about 1µF to thousands of µF. Mainly this type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc. Because this type of capacitor is comparatively similar to the nature of a coil in construction, it isn't possible to use for high-frequency circuits. (It is said that the frequency characteristic is bad.)

The photograph on the left is an example of the different values of electrolytic capacitors in which the capacitance and voltage differ.
From the left to right:
1µF (50V) [diameter 5 mm, high 12 mm]
47µF (16V) [diameter 6 mm, high 5 mm]
100µF (25V) [diameter 5 mm, high 11 mm]
220µF (25V) [diameter 8 mm, high 12 mm]
1000µF (50V) [diameter 18 mm, high 40 mm]

The size of the capacitor sometimes depends on the manufacturer. So the
sizes shown here on this page are just examples.

In the photograph to the right, the mark indicating the negative lead of the component can be seen.
You need to pay attention to the polarity indication so as not to make a mistake when you assemble the circuit.

Tantalum Capacitors

Tantalum Capacitors are electrolytic capacitors that is use a material called tantalum for the electrodes. Large values of capacitance similar to aluminum electrolytic capacitors can be obtained. Also, tantalum capacitors are superior to aluminum electrolytic capacitors in temperature and frequency characteristics. When tantalum powder is baked in order to solidify it, a crack forms inside. An electric charge can be stored on this crack.
These capacitors have polarity as well. Usually, the "+" symbol is used to show the positive component lead. Do not make a mistake with the polarity on these types.
Tantalum capacitors are a little bit more expensive than aluminum electrolytic capacitors. Capacitance can change with temperature as well as frequency, and these types are very stable. Therefore, tantalum capacitors are used for circuits which demand high stability in the capacitance values. Also, it is said to be common sense to use tantalum capacitors for analog signal systems, because the current-spike noise that occurs with aluminum electrolytic capacitors does not appear. Aluminum electrolytic capacitors are fine if you don't use them for circuits which need the high stability characteristics of tantalum capacitors.

The photograph on the left illustrates the tantalum capacitor.
The capacitance values are as follows, from the left:

0.33 µF (35V)
0.47 µF (35V)
10 µF (35V)

The "+" symbol is used to show the positive lead of the component. It is written on the body.

Ceramic Capacitors
Ceramic capacitors are constructed with materials such as titanium acid barium used as the dielectric. Internally, these capacitors are not constructed as a coil, so they can be used in high frequency applications. Typically, they are used in circuits which bypass high frequency signals to ground.
These capacitors have the shape of a disk. Their capacitance is comparatively small.

The capacitor on the left is a 100pF capacitor with a diameter of about 3 mm.
The capacitor on the right side is printed with 103, so 10 x 10³pF becomes 0.01 µF. The diameter of the disk is about 6 mm.
Ceramic capacitors have no polarity.
Ceramic capacitors should not be used for analog circuits, because they can distort the signal.

Multilayer Ceramic Capacitors

The multilayer ceramic capacitor has a many-layered dielectric. These capacitors are small in size, and have good temperature and frequency characteristics.
Square wave signals used in digital circuits can have a comparatively high frequency component included.
This capacitor is used to bypass the high frequency to ground.

In the photograph, the capacitance of the component on the left is displayed as 104. So, the capacitance is 10 x 10⁴ pF = 0.1 µF. The thickness is 2 mm, the height is 3 mm, the width is 4 mm.
The capacitor to the right has a capacitance of 103 (10 x 10³ pF = 0.01 µF). The height is 4 mm, the diameter of the round part is 2 mm.
These capacitors are not polarized. That is, they have no polarity.

Polystyrene Film Capacitors
In these devices, polystyrene film is used as the dielectric. This type of capacitor is not for use in high frequency circuits, because they are constructed like a coil inside. They are used well in filter circuits or timing circuits which run at several hundred KHz or less.

The component shown on the left has a red color due to the copper leaf used for the electrode. The silver color is due to the use of aluminum foil as the electrode.

The device on the left has a height of 10 mm, is 5 mm thick, and is rated 100pF.
The device in the middle has a height of 10 mm, 5.7 mm thickness, and is rated 1000pF.
The device on the right has a height of 24 mm, is 10 mm thick, and is rated 10000pF.
These devices have no polarity.

Electric Double Layer Capacitors (Super Capacitors)

This is a "Super Capacitor," which is quite a wonder.
The capacitance is 0.47 F (470,000 µF).
I have not used this capacitor in an actual circuit.

Care must be taken when using a capacitor with such a large capacitance in power supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of current when the capacitor is empty. For a brief moment, the capacitor is more like a short circuit. A protection circuit needs to be set up.

The size is small in spite of capacitance. Physically, the diameter is 21 mm, the height is 11 mm.
Care is necessary, because these devices do have polarity.

Polyester Film Capacitors
This capacitor uses thin polyester film as the dielectric.
They are not high tolerance, but they are cheap and handy. Their tolerance is about ±5% to ±10%.

From the left in the photograph
Capacitance: 0.001 µF (printed with 001K)
[the width 5 mm, the height 10 mm, the thickness 2 mm]
Capacitance: 0.1 µF (printed with 104K)
[the width 10 mm, the height 11 mm, the thickness 5mm]
Capacitance: 0.22 µF (printed with .22K)
[the width 13 mm, the height 18 mm, the thickness 7mm]

Care must be taken, because different manufacturers use different methods to denote the capacitance values.

Here are some other polyester film capacitors.

Starting from the left
Capacitance: 0.0047 µF (printed with 472K)
[the width 4mm, the height 6mm, the thickness 2mm]
Capacitance: 0.0068 µF (printed with 682K)
[the width 4mm, the height 6mm, the thickness 2mm]
Capacitance: 0.47 µF (printed with 474K)
[the width 11mm, the height 14mm, the thickness 7mm]

These capacitors have no polarity.

Polypropylene Capacitors
This capacitor is used when a higher tolerance is necessary than polyester capacitors offer. Polypropylene film is used for the dielectric. It is said that there is almost no change of capacitance in these devices if they are used with frequencies of 100KHz or less.
The pictured capacitors have a tolerance of ±1%.

From the left in the photograph
Capacitance: 0.01 µF (printed with 103F)
[the width 7mm, the height 7mm, the thickness 3mm]
Capacitance: 0.022 µF (printed with 223F)
[the width 7mm, the height 10mm, the thickness 4mm]
Capacitance: 0.1 µF (printed with 104F)
[the width 9mm, the height 11mm, the thickness 5mm]

When I measured the capacitance of a 0.01 µF capacitor with the meter which I have, the error was +0.2%.

These capacitors have no polarity.

Mica Capacitors

These capacitors use Mica for the dielectric. Mica capacitors have good stability because their temperature coefficient is small. Because their frequency characteristic is excellent, they are used for resonance circuits, and high frequency filters. Also, they have good insulation, and so can be utilized in high voltage circuits. It was often used for vacuum tube style radio transmitters, etc.
Mica capacitors do not have high values of capacitance, and they can be relatively expensive.

Pictured at the right are "Dipped mica capacitors." These can handle up to 500 volts.
The capacitance from the left
Capacitance: 47pF (printed with 470J)
[the width 7mm, the height 5mm, the thickness 4mm]
Capacitance: 220pF (printed with 221J)
[the width 10mm, the height 6mm, the thickness 4mm]
Capacitance: 1000pF (printed with 102J)
[the width 14mm, the height 9mm, the thickness 4mm]

These capacitors have no polarity.

Metallized Polyester Film Capacitors
These capacitors are a kind of a polyester film capacitor. Because their electrodes are thin, they can be miniaturized.

From the left in the photograph
Capacitance: 0.001µF (printed with 1n. n means nano:10^-9)
Breakdown voltage: 250V
[the width 8mm, the height 6mm, the thickness 2mm]
Capacitance: 0.22µF (printed with u22)
Breakdown voltage: 100V
[the width 8mm, the height 6mm, the thickness 3mm]
Capacitance: 2.2µF (printed with 2u2)
Breakdown voltage: 100V
[the width 15mm, the height 10mm, the thickness 8mm]
Care is necessary, because the component lead easily breaks off from these capacitors. Once lead has come off, there is no way to fix it. It must be discarded.

These capacitors have no polarity.

Variable Capacitors

Variable capacitors are used for adjustment etc. of frequency mainly.

On the left in the photograph is a "trimmer," which uses ceramic as the dielectric. Next to it on the right is one that uses polyester film for the dielectric.
The pictured components are meant to be mounted on a printed circuit board.

When adjusting the value of a variable capacitor, it is advisable to be careful.
One of the component's leads is connected to the adjustment screw of the capacitor. This means that the value of the capacitor can be affected by the capacitance of the screwdriver in your hand. It is better to use a special screwdriver to adjust these components.

Pictured in the upper left photograph are variable capacitors with the following specifications:
Capacitance: 20pF (3pF - 27pF measured)
[Thickness 6 mm, height 4.8 mm]
Their are different colors, as well. Blue: 7pF (2 - 9), white: 10pF (3 - 15), green: 30pF (5 - 35), brown: 60pF (8 - 72).

In the same photograph, the device on the right has the following specifications:
Capacitance: 30pF (5pF - 40pF measured)
[The width (long) 6.8 mm, width (short) 4.9 mm, and the height 5 mm]

The components in the photograph on the right are used for radio tuners, etc. They are called "Varicons" but this may be only in Japan.
The variable capacitor on the left in the photograph, uses air as the dielectric. It combines three independent capacitors.
For each one, the capacitance changed 2pF - 18pF. When the adjustment axis is turned, the capacitance of all 3 capacitors change simultaneously.
Physically, the device has a depth of 29 mm, and 17 mm width and height. (Not including the adjustment rod.)
There are various kinds of variable capacitor, chosen in accordance with the purpose for which they are needed. The pictured components are very small.

To the right in the photograph is a variable capacitor using polyester film as the dielectric. Two independent capacitors are combined.
The capacitance of one side changes 12pF - 150pF, while the other side changes from 11pF - 70pF.
Physically, it has a depth of 11mm, and 20mm width and height. (Not including the adjustment rod.)
The pictured device also has a small trimmer built in to each capacitor to allow for precise adjustment up to 15pF.

Coils

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 15:27:00 +0000

A coil is nothing more than copper wire wound in a spiral.
This symbol is used to indicate a coil in a circuit diagram.
Inductance value is designated in units called the Henry(H). The more wire the coil contains, the stronger its characteristics become. The inductance value can become quite large. If a coil is wound around an iron rod, or ferrite core (strengthened with iron powder), the inductance of the coil will be greatly increased. Coils used in typical electric circuits varely widely in values, ranging from a few micro-henry (µH) to many henry (H).

Coils are sometimes called "inductors." Inductance is the measure of the strength of a coil. Capacitors have capacitance, resistors have resistance, and Inductors (coils) have inductance. When alternating current flows through a coil, the magnetic flux that occurs in the coil changes with the current. When a second coil is put close to the first coil (with the changing flux), alternating voltage is caused to flow in the second coil by an effect known as "mutual induction." Mutual inductance (inductance) is measured in units of the Henry. The changing magnetic flux in a coil affects itself as well as other coils. This is called self induction, the degree of this self induction is called Self Inductance. Self inductance is a measure of a coil's ability to establish an induced voltage as a result of a change in its current. Self inductance is commonly referred to as simply "inductance," and is symbolized by "L". The unit of inductance is the Henry (H).

The definition of "Henry" is "When a current of 1 ampere flows through a given coil in 1 second such that 1 volt is induced to flow in a second coil, the mutual inductance between the coils is said to be 1 Henry." The definition of self inductance is the same, except that the 1 volt is induced in the first coil; there is no second coil.

Characteristic of coils
When wire is coiled, it takes on various characteristics that are different from straight wire. Below I will explain some of the characteristics coils that I know.

Current Stabilization Characteristic
When current begins to flow in the coil, the coil resists the flow. When current decreases, the coil makes current continue to flow (briefly) at the previous rate.
This is called "Lenz's law".
'The direction of induced current in a coil is such that is opposes the change in the magnetic field that procduced it.'

This characteristic is used for the ripple filter circuit of a power supply where it transforms alternating current(AC) to direct current(DC).
When a rectifier is used to make DC from AC, the output of the rectifier without a ripple filter circuit is ripple current. Ripple current is DC that has a large AC component.

A ripple filter circuit often combines coil and capacitors. The coil resists the change of current and capacitors supplement the flow of current by discharging into the circuit if the input voltage drops. Thus, clear, ripple-free DC is obtained from the ripple filter circuit.

Resistor is used instead of coil in simple ripple filter circuit.

Mutual induction
As I wrote above, electric power can be transfered between two coils by mutual induction.

The transformer utilizes this characteristic.
The input coil that gives the electric power is called the primary side, while the output coil that takes out the electric power is called the secondary side.
The output voltage is determined by the ratio of turns of wire between the primary coil and secondary coil.

Some transformers have a tap (or several) on the secondary coil to provide multiple voltage levels.

Electromagnet
When current flows through a conductor, a magnetic field is created. This field is much stronger in a coil. An electromagnet is just like a regular magnet. It attracts iron, nickel, and some other metals.

Relays utilize this characteristic.
When the current flows to the coil of relay, the magnetic field attracts a steel plate, and the switch that is attached to the steel plate goes ON. And the doorbell chime also utilizes electromagnets.

Resonance
When a coil and a capacitor are combined, the resulting circuit has special characteristics. The impedance (resistance to current flow) of the circuit changes with the frequency of the voltage. Current will flow easily at a given frequency, but has difficulty flowing at another frequency.
The tunning circut that select a particular radio station utilizes this characteristic.
Explaning resonance in more detail is very difficult. If you want to know more detail, please read further in a book about electronics.

High Frequency Coils
The photograph shows an example of a small coil component.
The component on the left is wound with thin copper wire to a small barbell-shaped ferrite core, and has a value of 100µH.
It is used for high frequency resonance, or for detering of high frequency.
As for size, the diameter is about 4 mm, the height about 7 mm.
The value of the small coil like this is indicated with a color code, just like a resistor.
The strengh of this type of coil varies from 1µH to several hundred µH.
1µH, 2.2µH, 3.3µH, 3.9µH, 4.7µH, 5.6µH, 6.8µH, 8.2µH, 10µH, 15µH, 18µH, 22µH, 27µH, 33µH, 39µH, 46µH, 56µH, 68µH, 82µH, 100µH other.

The second coil from the left has thin copper wire wound around a stick-shaped ferrite core.
It is used the same as the component above.
The value is 470µH. The diameter of the core is 4 mm, height is 10 mm, and the diameter of the coil is 8 mm.

The two devices on the right in the photograph are high frequency transformers.
They are used for intermediate frequency (455KHz) tuning of transistor radios, or for oscillator circuits.
To shield the coils from magnetic flux, and to prevent the coils from interfering with other circuits, the high frequency coils are housed in a metal case called shield case. This case must be connected to ground.
As for tuning or oscillation, this type of transformer can change its value of inductance.

Adjustment of the Inductance Value

The ferrite core of the coil is made like a screw. The core can be made to move in or out of the coil by turning it with a screwdriver.
A special plastic screwdriver is better to use for adjustment of the coils.
By moving the ferrite core in or out of the coil, the value of the coil's inductance can be changed.
The value of inductance can also be changed by changing the number of turns of wire that comprise the coil, but in fact it is not possible in any practical way. You want try it ?

The tuner of an FM radio handles very high frequencies (about 70MHz to 100MHz). The coils used in the tuning circuit are hollow; i.e. they have no ferrite core. A coil with a ferrite core has too much inductance too be used in such a circuit.
To adjust the inductance value of a hollow coil, the spacing between the loops of the coil is changed.
When you disassemble an FM radio, you may find these coils to appear a bit untidy. Do not try to "fix" the coil by making it a perfect set of loops. The coil has been bent intentionally, in order to be adjusted precisely.

The Toroidal Coil

The toroidal coil consists of copper wire wrapped around a cylindrical core. It is possible to make it so that the magnetic flux which occurs within the coil doesn't leak out, the coil efficiency is good, and that the magnetic flux has little influence on other components.

Resistors-Types of resistors

noreply@blogger.com (ASIF 007) — Sat, 03 Jul 2010 15:12:00 +0000

The resistor's function is to reduce the flow of electric current.
This symbol is used to indicate a resistor in a circuit diagram, known as a schematic.
Resistance value is designated in units called the "Ohm." A 1000 Ohm resistor is typically shown as 1K-Ohm ( kilo Ohm ), and 1000 K-Ohms is written as 1M-Ohm ( megohm ).

There are two classes of resistors; fixed resistors and the variable resistors. They are also classified according to the material from which they are made. The typical resistor is made of either carbon film or metal film. There are other types as well, but these are the most common.
The resistance value of the resistor is not the only thing to consider when selecting a resistor for use in a circuit. The "tolerance" and the electric power ratings of the resistor are also important.
The tolerance of a resistor denotes how close it is to the actual rated resistence value. For example, a ±5% tolerance would indicate a resistor that is within ±5% of the specified resistance value.
The power rating indicates how much power the resistor can safely tolerate. Just like you wouldn't use a 6 volt flashlight lamp to replace a burned out light in your house, you wouldn't use a 1/8 watt resistor when you should be using a 1/2 watt resistor.

The maximum rated power of the resistor is specified in Watts.
Power is calculated using the square of the current ( I² ) x the resistance value ( R ) of the resistor. If the maximum rating of the resistor is exceeded, it will become extremely hot, and even burn.
Resistors in electronic circuits are typicaly rated 1/8W, 1/4W, and 1/2W. 1/8W is almost always used in signal circuit applications.
When powering a light emitting diode, a comparatively large current flows through the resistor, so you need to consider the power rating of the resistor you choose.

Rating electric power

For example, to power a 5V circuit using a 12V supply, a three-terminal voltage regulator is usually used.

However, if you try to drop the voltage from 12V to 5V using only a resistor, then you need to calculate the power rating of the resistor as well as the resistance value.

At this time, the current consumed by the 5V circuit needs to be known.

Here are a few ways to find out how much current the circuit demands.

Assemble the circuit and measure the actual current used with a multi-meter.

Check the component's current use against a standard table.

Assume the current consumed is 100 mA (milliamps) in the following example.

7V must be dropped with the resistor. The resistance value of the resistor becomes 7V / 0.1A = 70(ohm). The consumption of electric power for this resistor becomes 0.1A x 0.1A x 70 ohm = 0.7W.

Generally, it's safe to choose a resistor which has a power rating of about twice the power consumption needed.

Resistance value

As for the standard resistance value, the values used can be divided like a logarithm. ( See

the logarithm table

)

For example, in the case of E3, The values [1], [2.2], [4.7] and [10] are used. They divide 10 into three, like a logarithm.

In the case of E6 : [1], [1.5], [2.2], [3.3], [4.7], [6.8], [10].

In the case of E12 : [1], [1.2], [1.5], [1.8], [2.2], [2.7], [3.3], [3.9], [4.7], [5.6], [6.8], [8.2], [10].

It is because of this that the resistance value is seen at a glance to be a discrete value.

The resistance value is displayed using

the color code

( the colored bars/the colored stripes ), because the average resistor is too small to have the value printed on it with numbers.

You had better learn the color code, because almost all resistors of 1/2W or less use the color code to display the resistance value.

Fixed Resistors

A fixed resistor is one in which the value of its resistance cannot change.

Carbon film resistors

This is the most general purpose, cheap resistor. Usually the tolerance of the resistance value is ±5%. Power ratings of 1/8W, 1/4W and 1/2W are frequently used.

Carbon film resistors have a disadvantage; they tend to be electrically noisy. Metal film resistors are recommended for use in analog circuits. However, I have never experienced any problems with this noise.

The physical size of the different resistors are as follows.

From the top of the photograph
1/8W
1/4W
1/2W

**Rough size**
Rating power (W)	Thickness (mm)	Length (mm)
1/8	2	3
1/4	2	6
1/2	3	9

This resistor is called a Single-In-Line(SIL) resistor network. It is made with many resistors of the same value, all in one package. One side of each resistor is connected with one side of all the other resistors inside. One example of its use would be to control the current in a circuit powering many light emitting diodes (LEDs).

In the photograph on the left, 8 resistors are housed in the package. Each of the leads on the package is one resistor. The ninth lead on the left side is the common lead. The face value of the resistance is printed. ( It depends on the supplier. )

Some resistor networks have a "4S" printed on the top of the resistor network. The 4S indicates that the package contains 4 independent resistors that are not wired together inside. The housing has eight leads instead of nine. The internal wiring of these typical resistor networks has been illustrated below. The size (black part) of the resistor network which I have is as follows: For the type with 9 leads, the thickness is 1.8 mm, the height 5mm, and the width 23 mm. For the types with 8 component leads, the thickness is 1.8 mm, the height 5 mm, and the width 20 mm.

Metal film resistors

Metal film resistors are used when a higher tolerance (more accurate value) is needed. They are much more accurate in value than carbon film resistors. They have about ±0.05% tolerance. They have about ±0.05% tolerance. I don't use any high tolerance resistors in my circuits. Resistors that are about ±1% are more than sufficient. Ni-Cr (Nichrome) seems to be used for the material of resistor. The metal film resistor is used for bridge circuits, filter circuits, and low-noise analog signal circuits.

From the top of the photograph
1/8W (tolerance ±1%)
1/4W (tolerance ±1%)
1W (tolerance ±5%)
2W (tolerance ±5%)

**Rough size**
Rating power (W)	Thickness (mm)	Length (mm)
1/8	2	3
1/4	2	6
1	3.5	12
2	5	15

Variable Resistors

There are two general ways in which variable resistors are used. One is the variable resistor which value is easily changed, like the volume adjustment of Radio. The other is semi-fixed resistor that is not meant to be adjusted by anyone but a technician. It is used to adjust the operating condition of the circuit by the technician. Semi-fixed resistors are used to compensate for the inaccuracies of the resistors, and to fine-tune a circuit. The rotation angle of the variable resistor is usually about 300 degrees. Some variable resistors must be turned many times to use the whole range of resistance they offer. This allows for very precise adjustments of their value. These are called "Potentiometers" or "Trimmer Potentiometers."

In the photograph to the left, the variable resistor typically used for volume controls can be seen on the far right. Its value is very easy to adjust.

The four resistors at the center of the photograph are the semi-fixed type. These ones are mounted on the printed circuit board.

The two resistors on the left are the trimmer potentiometers.

This symbol

is used to indicate a variable resistor in a circuit diagram.

There are three ways in which a variable resistor's value can change according to the rotation angle of its axis.

When type "A" rotates clockwise, at first, the resistance value changes slowly and then in the second half of its axis, it changes very quickly.

The "A" type variable resistor is typically used for the volume control of a radio, for example. It is well suited to adjust a low sound subtly. It suits the characteristics of the ear. The ear hears low sound changes well, but isn't as sensitive to small changes in loud sounds. A larger change is needed as the volume is increased. These "A" type variable resistors are sometimes called "audio taper" potentiometers.

As for type "B", the rotation of the axis and the change of the resistance value are directly related. The rate of change is the same, or linear, throughout the sweep of the axis. This type suits a resistance value adjustment in a circuit, a balance circuit and so on.

They are sometimes called "linear taper" potentiometers.

Type "C" changes exactly the opposite way to type "A". In the early stages of the rotation of the axis, the resistance value changes rapidly, and in the second half, the change occurs more slowly. This type isn't too much used. It is a special use.

As for the variable resistor, most are type "A" or type "B".

CDS Elements

Some components can change resistance value by changes in the amount of light hitting them. One type is the Cadmium Sulfide Photocell. (Cd) The more light that hits it, the smaller its resistance value becomes.

There are many types of these devices. They vary according to light sensitivity, size, resistance value etc.

Pictured at the left is a typical CDS photocell. Its diameter is 8 mm, 4 mm high, with a cylinder form. When bright light is hitting it, the value is about 200 ohms, and when in the dark, the resistance value is about 2M ohms.
This device is using for the head lamp illumination confirmation device of the car, for example.

Other Resistors

There is another type of resistor other than the carbon-film type and the metal film resistors. It is the wirewound resistor.

A wirewound resistor is made of metal resistance wire, and because of this, they can be manufactured to precise values. Also, high-wattage resistors can be made by using a thick wire material. Wirewound resistors cannot be used for high-frequency circuits. Coils are used in high frequency circuits. Since a wirewound resistor is a wire wrapped around an insulator, it is also a coil, in a manner of speaking. Using one could change the behavior of the circuit. Still another type of resistor is the Ceramic resistor. These are wirewound resistors in a ceramic case, strengthened with a special cement. They have very high power ratings, from 1 or 2 watts to dozens of watts. These resistors can become extremely hot when used for high power applications, and this must be taken into account when designing the circuit. These devices can easily get hot enough to burn you if you touch one.

		The photograph on the left is of wirewound resistors. The upper one is 10W and is the length of 45 mm, 13 mm thickness. The lower one is 50W and is the length of 75 mm, 29 mm thickness. The upper one is has metal fittings attached. These devices are insulated with a ceramic coating.

		The photograph on above is a ceramic (or cement) resistor of 5W and is the height of 9 mm, 9 mm depth, 22 mm width.

Thermistor ( Thermally sensitive resistor )

The resistance value of the thermistor changes according to temperature.
This part is used as a temperature sensor.

There are mainly three types of thermistor.

NTC(Negative Temperature Coefficient Thermistor)

: With this type, the resistance value decreases continuously as the temperature rises.

PTC(Positive Temperature Coefficient Thermistor)

: With this type, the resistance value increases suddenly when the temperature rises above a specific point.

CTR(Critical Temperature Resister Thermistor)

: With this type, the resistance value decreases suddenly when the temperature rises above a specific point.

The NTC type is used for the temperature control.

The relation between the temperature and the resistance value of the NTC type can be calculated using the following formula.

R	: The resistance value at the temperature T
T	: The temperature [K]
R₀	: The resistance value at the reference temperature T₀
T₀	: The reference temperature [K]
B	: The coefficient

As the reference temperature, typically, 25°C is used.

The unit with the temperature is the absolute temperature(Value of which 0 was -273°C) in K(Kelvin).

25°C are the 298 kelvins.

Resistor color code

Color	Value	Multiplier	Tolerance (%)
Black	0	0	-
Brown	1	1	±1
Red	2	2	±2
Orange	3	3	±0.05
Yellow	4	4	-
Green	5	5	±0.5
Blue	6	6	±0.25
Violet	7	7	±0.1
Gray	8	8	-
White	9	9	-
Gold	-	-1	±5
Silver	-	-2	±10
None	-	-	±20

Example 1
(Brown=1),(Black=0),(Orange=3)
10 x 10³ = 10k ohm
Tolerance(Gold) = ±5%

Example 2
(Yellow=4),(Violet=7),(Black=0),(Red=2)
470 x 10² = 47k ohm
Tolerance(Brown) = ±1%