BookMark Magazine ......... Education with Imagination .......

2020-08-08T17:50:00.001-07:00

Aspen Lasers Efficacy Web Site References

2020-08-04T12:05:00.002-07:00

In this set of articles, the efficacy of ultrasound and laser light treatments for brain injury, tendinosis, wound healing, carpal tunnel syndrome, back and shoulder pain, ankle sprain, diabetic neuropathy are discussed.

The article citations are all from Aspen Lasers web site: site: aspenlasers.com efficacy

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a randomized controlled trial for the efficacy of therapeutic ...

aspenlasers.com › wp-content › uploads › 2016/07 › Tendinosis

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by D Roberts

EFFICACY OF THERAPEUTIC CLASS IV LASER. TREATMENT FOR TENDINOSIS. Authors: Delia Roberts, FACSM, Selkirk College, Castlegar, BC, Canada;.

Treatments for Traumatic Brain Injury With ... - Aspen Laser

aspenlasers.com › wp-content › uploads › 2017/11 › STUDY-TBI-LA...

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by LD Morries - ‎Cited by 87 - ‎Related articles

We demonstrate greater clinical efficacy with higher fluence, in contrast to the bimodal model of efficacy previously proposed. In ten patients with chronic TBI ( ...

TREATMENT OF AN ACUTE DIsC HERNIATION REsULTING ...

aspenlasers.com › wp-content › uploads › 2016/07 › Disc-Herniation-...

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To demonstrate the efficacy of High Power Laser. Therapy as a treatment solution for a patient with an acute disc herniation non-responsive to traditional.

Wound Healing - Aspen Laser University

aspenlasers.com › wp-content › uploads › 2016/07 › Wound-Healing

by MD Skopin - ‎Related articles

To investigate the efficacy of low-level exposure to. 980 nm laser light, we have measured cell growth rates following wound induction using an in vitro model of ...

the long term management of diabetic neuropathy with high ...

aspenlasers.com › wp-content › uploads › 2016/07 › Neuropathy-Dia...

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OBJECTIVE: To demonstrate the efficacy of High Power Laser. Therapy as a treatment solution for a patient with chronic non-responsive peripheral neuropathy.

class iv laser therapy: effective for back and neck/shoulder pain

aspenlasers.com › wp-content › uploads › 2016/07

efficacy and safety of the combination and generate preliminary results for a randomized controlled trial. METHODS: Between 9/2009 and 2/2010, a total of 55 ...

Ankle Sprain - Semantic Scholar

aspenlasers.com › wp-content › uploads › 2016/07 › Ankle-Sprain-Cl...

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by M Steve Scher - ‎Related articles

blind randomized controlled trail of the efficacy of using ultrasound to treat lateral ankle sprains. The trail reported that ultrasound is not a better form of treatment ...

treatment of achilles tendinitis with class iv infrared - Aspen ...

aspenlasers.com › wp-content › uploads › 2016/07 › Achilles-Tendini...

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pressure to demonstrate efficacy of treatment the. FDA provided clearance of the use of “Low-Level”. Class III therapeutic lasers in 2002 and “High Power”.

Reimbursement Guide for Healthcare Professionals Offering ...

aspenlasers.com › wp-content › uploads › 2016/09 › Reimbursement-...

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validate the efficacy of Class IV Laser Therapy. Taking a passive, “wait and see” approach would inevitably lead to further delays in obtaining CPT coding due to ...

Effectiveness of Low Level Laser in the Treatment of Carpal ...

aspenlasers.com › CarpalTunnelSyndrome-LaserTherapyTreatments

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by F Isra'a - ‎2012 - ‎Related articles

M. (2003): Efficacy of low power laser therapy and exercise on pain and functions in chronic low back pain. Lasers Surg. Med. 32(3): 233-8. Sattayut S, Hughes F ...

SOC Chips and Memory Design

2020-04-05T19:45:00.000-07:00

A System-On-A-Chip, or SOC is understood to mean a chip that includes one or more microprocessors (cores) and any number of associated peripheral chips. The definition is not a hard definition. Often a SOC is categorized as any chip whose function performs that of any electronic system regardless of whether or not it has a microprocessor or not. The origin of SOC terminology dates back to the 1980s when the idea of a PC on a chip was introduced. At that point in time integrated circuit technology had advanced to a point that more than just a microprocessor could be integrated into a single chip.

A typical microprocessor system then basically consisted of a microprocessor, a memory controller and an IO controller. Memory controllers are used to access DRAM, Flash, SRAM and ROM memory banks within the computers memory. IO controllers are used to access serial and parallel peripheral devices such as disk drives, USB ports, the keyboard, the mouse, and the screen. Another chip that can be found in the classic PC is a DMA controller. A DMA controller, which can be also classified as an IO controller, is used to access main memory without the need for microprocessor intervention. This lowers memory access time and lowers overall power consumption. At the same time it frees the microprocessor to perform other processing tasks.

Today a SOC includes much more than a microprocessor and a few peripheral control chips. For example, the SnapDragon line of mobile phone processing chips include up to eight microprocessor cores, a graphic processing unit. a DSP processor, a security processor, cache tag and data SRAM memory as well as a DDR SDRAM and cache memory controller.

The block diagram below shows a SOC chip that includes two microprocessor cores, data cache SRAM, a SDRAM DDR controller and a cache controller with a content addressable memory (CAM). Having the data cache SRAM on chip speeds memory accesses and lowers power consumption. Sending data off chip always increases delay time and raises power consumption This is because the internal chip does not have the high capacitance associated with PC traces and the input and outputs of a chip's pins.

The integrate cache controller, CAM and data cache are critical to improving memory access time

The CAM also speeds memory access time. The CAM is a special type of memory that uses a digital comparator to locate data at an address in a high speed data cache SRAM. The cache tag SRAM, or CAM, contains the addressees of the data that the microprocessor uses most often. When the microprocessor sends out an address to the cache tag a bank of comparators within the cache tag compares the microprocessor address in each CAM location simultaneously to see if that address is in the CAM. If there is an address match, the data location that matches that address signals a "hit." The cache tag controller then accesses the data cache SRAM address so the microprocessor can read the data.

One of the reasons why CAMs are so much faster than SRAMs or DRAMs is that a comparator instead of a decoder is used to locate an address location. A decoder has several layers of logic that introduce delays in accessing a memory's data. DRAMs because of their much more complex decoding scheme are slower than SRAMs. The key point to remember about cache memory architecture is that it allows data that is used most often to stay in localized high speed SRAM memory. This means accesses to slower DRAMs, FLASH and disk drives are minimized. In fact, accesses to slower memory devices can be reduced by as much as 98 percent.

Diet as a Coronavirus Prevention Method

2020-04-01T12:45:00.002-07:00

How to Protect Yourself Against the Coronavirus is an important question with lots of different answers. One idea is to focus on foods with natural antibiotics built in. This would include many spices like ginger. Garlic and grapefruit juice are also known for their antibiotic capabilities. Another idea is to try an alkaline diet. These diets stay away from acidic foods that are high in phosphorus. There is naturally skepticism about natural antibiotics. Worries include their interaction with doctor prescribed drugs.

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This is a pen and ink rendition from Alice and Wonderland. Flying playing cards swirling about Alice. The illustration depicts the panic and uncertainty of the situation. • Millions of unique designs by independent artists. Find your thing.

Nineteen New Statistics QuickNotes from BookMarkTutoring.com

2020-03-16T21:42:00.000-07:00

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BookMark Magazine ......... Education with Imagination .......: New Algebra Cheat Sheet Stickers, Prints, Posters

2020-02-19T15:36:00.001-08:00

BookMark Magazine ......... Education with Imagination .......: New Algebra Cheat Sheet Stickers, Prints, Posters: Need to calculate the distance between two points? These QuickNote stickers have all you need, equation and example. Also has penguin walkin...

New Algebra Cheat Sheet Stickers, Prints, Posters

2020-02-19T15:22:00.001-08:00

Need to calculate the distance between two points? These QuickNote stickers have all you need, equation and example. Also has penguin walking boots so you can go the distance. Add it to your Algebra sticker collection today. The Distance Formula joins the growing list of Algebra QuickNote Quick Stick products from BookmarkTutoring, specialist in online sticker based tutoring.

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RLC Series Resonant Frequency Calculator

2017-11-02T00:19:00.000-07:00

When a capacitor, resistor and inductor are connected in series, a series resonant circuit is formed. A series resonant circuit has a frequency response that has a minimum reactance and maximum gain at the resonant frequency. The series resonant circuit effectively acts as a bandpass filter.

The resonance frequency for a series resonant circult can be calculated with the formula:

fr = 1/2*PI*SQR(LC)

Where

Fr = Resonant Frequency in Hertz
PI = 3.14
L = Inductance in Henries
C = Capacitance in Farads

The formula can be derived by equating the inductive reactance to the capacitive reactance in a series circuit and then solving for the frequency.

Series Resonance Frequency Calculator

To calculate the resonance frequency, you can use the calculator below. For the calculator, enter in the inductance and capacitance. The resulting resonant frequency is then calculated. You can also use the up and down arrow keys to change the values of inductance and capacitance and compute the resonant frequency in real time. For calculating the resonant frequency, the resistor value is not needed. The resonant frequency is only dependent on the inductance and the capacitance.

Frequency Resonance Calculator: Series RLC Circuits

2017-11-01T19:09:00.001-07:00

When a capacitor, resistor and inductor are connected in series, a series resonant circuit is formed. A series resonant circuit has a frequency response that has a minimum reactance and maximum gain at the resonant frequency. The series resonant circuit effectively acts as a bandpass filter.

The resonance frequency for a series resonant circult can be calculated with the formula:

fr = 1/2*PI*SQR(LC)

Where

Fr = Resonant Frequency in Hertz
PI = 3.14
L = Inductance in Henries
C = Capacitance in Farads

The formula can be derived by equating the inductive reactance to the capacitive reactance in a series circuit and then solving for the frequency.

Series Resonance Frequency Calculator

To calculate the resonance frequency, you can use the calculator below. For the calculator, enter in the inductance in milliHenries (mH) and capacitance in microFarads(uF). The resulting resonant frequency is given in Hertz.

Inductive Reactance Calculator and Tutorial

2017-10-31T21:32:00.000-07:00

Inductive reactance is the inductor equivalent to the resistance of a resistor. Unlike a resistor, a inductor's reactance is directly proportional to frequency. An inductor exhibits zero reactance to a DC (0 Hertz) signal. As frequency goes up, the inductive reactance will goes up. At very high frequencies the capacitive reactance of circuit approaches infinity. For this reason, inductors are shorts to DC signals and open circuits to high frequencies. .

The formula for calculating capacitive reactance is:

Equation 1: Xl = 2*PI*F*L

where

Xl is the inductove reactance in Ohms
PI is the constant 3.14
F is the frequency in Hertz
L is the value of the inductance in Henries

Inductance Reactance Calculator

You can see how the inductive eactance changes with frequency and capacitance using the inductance reactance calculator below. Enter in the inductance in uH (microHenires) and the frequency in Hertz. If you enter in 0 for the frequency the calculator calculates an answer of 0. If you want to change the frequency easily, after you enter a number in the frequency box, simply hold down the up or down arrow keys on your keyboard.

What you will notice with this calculator, is that the inductive reactance is relatively low for low frequencies and low values of inductances. In order to increase the inductive reactance substancially, you will need a frequency in the megahertz region or an inductor that is in the range of of millihenries.

Capacitive Reactance Calculator and Tutorial

2017-08-31T13:25:00.004-07:00

Capacitive reactance is the capacitor equivalent to the resistance of a resistor. Unlike a resistor, a capacitor's reactance is inversely proportional to frequency. A capacitor exhibits an infinite reactance to a DC (0 Hertz) signal. As frequency goes up, the capacitive reactance will go down. At very high frequencies the capacitive reactance of circuit approaches zero.

The formula for calculating capacitive reactance is:

Equation 1: Xc = 1/(2*PI*F*C)

where

Xc is the capacitive reactance in Ohms
PI is the constant 3.14
F is the frequency in Hertz
C is the value of the capacitor in Farads

Capacitance Reactance Calculator

You can see how the capacitive reactance changes with frequency and capacitance using the capacitance reactance calculator below. Enter in the capacitance in uF and the frequency. If you enter in 0 for the frequency the calculator calculates an answer of infinity. If you want to change the frequency easily, after you enter a number in the frequency box, simply hold down the up or down arrow keys on your keyboard.

Resistors in Parallel: Electronics Tutorial #10, BookMarkTutoring.com

2017-08-30T23:23:00.000-07:00

Placing resistors in parallel reduces the overall resistance of a circuit. The equation for calculating the equivalent resistance of two or more resistors in parallel is

Equation 1: Req = 1/(1/R1 + 1/R2 + 1/R3 + ..... + 1/Rn)

For the circuit shown below, where R1 = 2 Ohms, R2 = 4 Ohms and R3 = 4 Ohms, the equivalent resistance calculated with equation 1 is

Req = 1/(1/R1 + 1/R2 + 1/R3)

Req = 1/(1/2 + 1/4 + 1/4) = 1/(6/12 + 3/12 + 3/12) = 1/(12/12) = 1 Ohm

The equivalent resistance of resistors in parallel is always lower than the lowest value resistor

Circuit Applications

Resistors are often placed in parallel to construct a resistor that doesn't come in a standard value or, in many cases, to allow the use of resistors with lower power ratings. When resistors are placed in parallel the current splits between the different branches in the parallel circuit. The amount of current in each branch is proportional to the resistance in each branch. Branches with lower resistance will conduct more current.

Another reason to place resistors in parallel is even heat distribution. Current flow results in energy dissipation which in turn results in heat. If one resistor is used instead of several resistors in parallel the heat will be more concentrated on the circuit board. As well, the large resistor will need a higher power rating. The higher levels of concentrated heat may result in a design that has a lower mean time between failure. This can be especially true in designs that must carry a significant amount of current.

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Voltage Dividers: Electronics Tutorials #9

2017-08-30T22:09:00.003-07:00

A voltage divider is most often used to provide a voltage that is a fraction of a battery voltage. It most often consists of two resistors that are connected in series with a battery. The ratio of the resistors determines the output voltage from the voltage divider.

The formula for calculating the output voltage of a voltage divider with two resistors connected to a battery is

Equation 1: Vout= Vbattery*R2/(R1 + R2)

The circuit diagram below shows a voltage divider connected to a 10 V battery. With the 2000 and 3000 ohm resistors, the output voltage is calculated from equation 1 as

Vout = 10*3000/(2000 + 3000) = 6 Volts

The idea can be extended to any number of resistors to obtain any fractional output voltage desired. The formula comes about by dividing the applied voltage across the total series resistance to obtain the current. In the example above the current is 2 mA (10V/5000 Ohms). The current multiplied by the resistor will give the voltage drop across the resistor.

Voltage Buffers

Often when a voltage divider is used to supply a different voltage than a battery voltage, a voltage buffer is placed at the output voltage node of the voltage divider. A voltage buffer, because it does not draw any current (or very little), will not change the output voltage of the voltage divider. Voltage buffers are often made from transistor devices such as JFETs and MOSFETs.

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Inductors in Series: Electronics Tutorial #8, BookMarkTutoring.com

2017-08-30T15:57:00.003-07:00

Inductors in series add. The formula for inductors in series is

Equation 1: Leq = L1 + L2 + L3 + ...... Ln

In the figure below, the equivalent inductance is calculated using equation 1 as

Leq = 1mH + 2mH + 5mH = 8mH

Inductors in Series Add

Units

Inductance is measured in Henries (H). A milliHenry (mH) is one-thousandth of a Henry. Inductors generally range in value from nanoHenries (nH) to milliHenries. An inductor in the milliHenry range is a large inductor. Because of its size, it can store a large amount of energy. The more energy an inductor can store, the more power it can generate and the higher potential of dangerous electrical shock.

Electrical Specifications

Inductors have associated with them a resistance. They also have a rated current. The rated current should not be exceeded. For inductors in series, the inductor with the lowest rated current determines the maximum amount of current that the series circuit can safely pass.

Applications

Inductors are used as electronic filters, in induction motors and in transformers. They are also used extensively in power supplies. RF chip inductors are used in cell phones, local area networks and other high frequency circuits in the 10 MHz to GHz range.

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Learning Links

Basic Facts About Inductors

Capacitors in Parallel: Electronics Tutorial # 7

2017-08-30T14:31:00.002-07:00

When capacitors are placed in parallel, capacitors add. The equivalent capacitance of capacitors in parallel can be calculated from the formula:

Equation 1: Ceq = C1 + C2 + C3 + C4 + ..... + CN

For the circuit below, the equivalent capacitance is calculated with equation 1 as"

Ceq = 1uF + 2uF + 2uF + 3uF = 8uF

Add Capacitors in Parallel to Obtain the Equivalent Capacitance

Capacitors are measured in units of Farads. A uF or microFarad, is one millionth of a Farad. For the above example, the equivalent capacitance is 8 microFarads.

Applications

Capacitors are often placed in parallel to increase the capacitance to a specific value that is not available as a standard component. In DC power supply application, smaller capacitors are put in parallel because smaller capacitors will filter out ripple better than one large equivalent capacitor. Parallel capacitors are often used in Kinetic Energy Conversion systems (used in electric cars).

Limits

Capacitors can be placed in parallel, but in practice, the total amount of voltage that can be applied across capacitor in parallel can not exceed the lowest capacitor voltage rating of the capacitors within the parallel bank.

Learning Links

Bookmark Tutoring.com

Capacitors in Parallel

Resistors in Series: BookMark Electronics Tutorial #6

2017-08-30T11:20:00.001-07:00

Placing resistors in series allows you to create higher resistance values. And thats because resistors in series add. Resistors in series have the same current flowing through them. The equation for resistors in series is

Equation 1 Req = R1 + R2 + R3 + ...... + Rn

For the example below, there are four resistors in series. The equivalent resistance is equal to the sum of the resistors: Req = 100 + 200 + 300 + 200 = 800 Ohms

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Electronics Tutorial #4: Ohms Law

2017-08-30T00:01:00.001-07:00

If you want to build your own electronic circuits, one law you must learn and know how to use is Ohms law. Ohms law lets you calculate the current and voltage through and across a resistor. The basic equation that Ohms law states is that voltage is equal to the product of current and resistance. In equation form:

Equation 1: V= IR

If you know the voltage across a resistor and the current through a resistor you can compute the value of the resistor. Similarly, if you know the resistor value and the current through the resistor you can compute the voltage across the resistor. For example if you put 2 Volts across a 1 Ohm resistor, from Ohms law you calculate that the current is 1 Ampere.

If you don't want to do the hand calculations required for Ohms law, you can always use a circuit simulator. The LTSpice circuit simulator, is a free simulator, that you can use to calculate the voltage across and the current through a resistor. In the LTSpice circuit schematic below, a 10 Volt battery is placed across a 1000 Ohm resistor. Using Ohms law, you can calculate that the current through the resistors would be 0.01 Ampere or 10 mA. A mA (milliamp) is 1/1000th of an Ampere.

LTSPICE Ohms Law Circuit Simulation

There are many advantages of using the LTSpice circuit simulator to analyze a circuit. One advantage is that it eliminates calculation errors. The second advantage is that you can analyze complex circuits, that would take hours of hand calculations, in seconds. The third advantage is that it facilitates learning and allows you to build intuition about circuit design.

For more information visit www.bookmarktutoring.com

Learning Links

LTSPICE Download

Electronics Tutorial #3, JFET Common Source Amplifiers

2017-08-29T21:49:00.001-07:00

If you are a do-it-yourself electronic hobbyists or an audio enthusiast, one of the first types of circuits you want to add to your circuit collection is an amplifier. Amplifiers can be found in all sorts of electronic equipment and devices. Headphones, mixers, cell phones, PCs, stereos and radios are just a few audio applications. Medical devices, such as hearing aids and biomedical instrumentation, such as radiation sensors, also employ amplifiers. But the applications of amplifiers doesn't stop there. Robots are another area where amplifiers and sensors work together to bring new forms of artificial life.

High-quality amplifiers can be built relatively easily and inexpensively using JFET transistors. JFET transistors have low-noise and low-power characteristics that make them well-suited for high-end audio and scientific applications.

One of the most common types of JFET amplifiers is the common source amplifier. It is used to amplify a low voltage audio signal, such as which comes from a microphone. Once amplified, the signal can be into a speaker, such as those found in cell phones and tablets.

JFET Common Source Amplifier Design

The basic design of a JFET common source amplifier is shown below. In this design, a 1 Volt peak to peak sine wave is fed into the circuit. The amplifier increases the voltage level to 5 V peak to peak. The voltage gain of the circuit is controlled with the resistors in the circuit. In this case, since the drain resistor, Rd, is 4000 Ohms, and the source resistor, Rs, is 400 Ohms, the gain is 5 By increasing the ratio of Rd to Rs you can increase the voltage gain. Similarly, reducing the ratio reduces the gain.

Common Source Amplifier: LTSpice Schematic

LTSpice Simulation Voltage Gain of Common Source Amplifier

Designing the Amplifier: Bias Point Considerations

The design of a common source amplifier requires that you first determine the DC bias point. This can be determined with an LTSpice simulation. The figure below shows the results of applying a 0 V signal to the input and the resulting output bias voltages and currents. As can be seen the DC output voltage determines the base line for the output waveform, In this case, its 10.7 volts. This can be calculated using a variety of different methods. However, often its just easier to determine it from an LTSpice simulation.

LTSpice DC Bias Point Simulation

The DC output voltage can be changed if you want. You could change the values of the Rd and Rs resistors, but this will alter the gain of the circuit. Alternately, you could bias the gate with a DC voltage through a resistor or using a voltage divider.

Voltage Gain

The voltage gain of the circuit can be calculated from the voltage gain equation for a common source amplifier:

Equation 1: Av = -gm *Rd)/(1 + gm*Rs)

The equation requires that you know the transductance, gm, of the transistor. The transconductance however is also a function of the bias point, specifically Vgsq. The transconductance can also be estimated from the data sheet of the manufacturer. Using an approximate estimate of the transconductance will give you a good idea of the gain. For this example, the transconductance of the LSK489 is estimated at 2.5 mA/V. Substituting this value into the equation along with the values of the Rd and Rs gives a voltage gain of -5.

In order for equation 1 to be valid, the value of Rd must be at least 10 times smaller than the drain resistance of the actual JFET. From the IV curves of the LSK489, the value of rd around the bias point is in the order of 50k.

All in all though, it is often easier to determine the gain very roughly with an estimated constant. For example, Av = 1/2(Rd/Rs) gives a good approximation.

Building the Circuit

If you want to breadboard the circuit, you can use a variety of different JFETs. For this example the LKS489, JFET N-Channel transistor from Linear Integrated Systems was used. This JFET has a pinchoff voltage that ranges between -1.5 and -3.5 Volts. The drain to source saturation current for the LSK489 ranges from 2.5 to 15 mA. The transconductance ranges from around 1 millisiemens upward to 8 millisiemens (ma/V).

If you substitute different JFETs into your breadboard, you will find that the bias point and the gain will vary. This is a direct result of the fact that different JFETs have different pinchoff voltages, IDSS and transconductance specifications.

When building the actual circuit with the LSK489 you will also find that the gain and bias point may not be what the simulator predicts. This is because JFET specifications vary from device to device and from run to run. However they always fall in between the minimum and maximum limits.

To overcome this problem, amplifier manufacturers go to great lengths to test each JFET for tighter specification limits. There are also a number of design techniques that can be used to eliminate variations in gain as a result of variations in JFET specifications.

For more information visit www.bookmarktutoring.com.

Learning Links

Junction Field Effect TransistorTheory and Applications
LSK489 Data Sheet

Electronics Tutorial: Diode Connected JFET for Overvoltage Protection Applications

2017-08-27T21:43:00.003-07:00

If you need to protect sensitive circuits from overvoltage breakdown conditions, diodes are one way. When the input voltage becomes to high, the diode will conduct and limit the voltage to around 0.7 volt. However, if your circuit is used to measure low-level currents, even a slightly biased diode can siphon off a significant amount of current - seriously degrading measurement accuracy

In order to keep your measurements accurate and protect your measurement circuitry you will need a diode that has a very low current in the non conduction region (below the forward bias voltage). In this case, a JFET connected diode is an alternative. When a JFET is connected as a diode, it exhibits very low levels of leakage current in the non-conduction region.

A JFET connected diode is simple to build. Just connect the source and the drain of an N-Channel JFET together. The gate of the JFET will serve as the cathode and the drain/source will be the anode. Such a connection is shown in the LTSpice schematic below. For this circuit, a 1 Volt sine wave (at 300 Hz) is applied to the JFET diode.

A diode can be easily constructed with an N-Channel JFET

The output of the JFET diode is taken across the load resistor, R1, Just like a regular diode, it will clip the negative portion of a sine wave. Also just like a regular diode, it will not conduct until the driving voltage reaches 0.7 volt. This shortens the duty cycle of the output waveform and lowers the peak voltage of the output waveform.

The JFET diode clips the negative cycle of a sine wave

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LEARNING LINKS

Diode Connected JFET Protects Op Amps
Common Circuit Applications (JFET Diode)

Electronics Tutorial: JFET Current Voltage Characteristics: IV Curves with LTSpice

2017-08-27T17:54:00.001-07:00

LTSpice offers one way to generate IV curves without an expensive curve tracer. However, how well LTSpice IV curves match the actual device’s IV curves depends on how accurately the JFET model matches the actual device. Not all LTSpice models are created equal. Some models are bare bones and will only give you a a rough estimate of the actual IV curves. Most models include the pinchoff voltage and beta parameter, which take into account the drain to source saturation current. Additionally, most models are only specified for a given set of process conditions. This process condition most often corresponds to the minimum data specifications on the data sheet.

JFET IV Characteristics (Curve Tracing)

The basic circuit for generating IV curves for a N channel is shown below. It utilizes two supplies, one for generating the gate to source voltage (VGS) and one for generating the drain to source voltage (VDS). During the simulation, the gate to source voltage is kept constant and the drain to source voltage is stepped from 0 Volts to a maximum drain to source voltage.

However, a complete set of IV curves requires that the drain-to-source current be measured at different VGS voltages. The typical LTSpice simulation command for generating a set of JFET IV curves is

.DC VDS 0 15 0.01 VGS -1.5 0 -0.3

LTSPICE Circuit Schematic for Generating IV Curves for a JFET

Th e DC sweep command instructs the simulator to first set the gate voltage to -1.5 volts and then sweep the VDS power supply from 0 to 15 volts in 0.01 volt steps. Once that sweep is complete, the VGS supply is incremented by -0.5 Volts to -1.5 Volts and VDS is swept again from 0 to 15 volts This process continues until VGS reaches 0 V. A N-Channel JFET is fully on when the gate-to-source voltage is 0 V. When VGS is at the pinchoff voltage the drain to source current is zero. For the default JFET LTSPICE model used in this example, the pinchoff parameter is at its default value of - 2 Volts.

IV Characteristics of Default N-Channel JFET LTSPICE Model

The default N-Channel default model also uses LAMBA = 0. Because LAMBDA is zero, the slope of the IV curves in the saturation region is zero also. For the most part, this is not the way a real JFET operates. The IV curves in the saturation region have a small slope, which is set with the value of LAMBDA.

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LEARNING LINKS

JFET SPICE DEFAULTS: http://ltwiki.org/index.php5?title=J_JFET_transistor

LTSPICE TUTORIAL http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_6.htm

ACT Math Learning Points ..

2016-08-03T23:20:00.001-07:00

ACT MATHEMATICS

Learning Point Checklist

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If you want to do well on the ACT, you will need to make sure you know what the test covers. Below find over 100 Learning Points that the math test specification for the ACT covers. These include numerous specific topics from basic math, algebra I and II, and geometry. The ACT also focuses on the probability, statistics, and trigonometry that is covered in high school algebra II. Studies from the ACT testing organization have shown that students who have taken math up to and including precalculus score much higher than those that haven't.

BookMarkTutoring.com uses ACT Math Learning Points in conjunction with the students math grades to determine exactly where students should focus on to improve their ACT score in the most efficient and effective manner.

	Basic Operations and Applications
1	Whole number and decimals
2	Simple unit conversions
3	Percent
4	Rate and proportion
5	Tax added percentage
6	Average computations
7	Rate based unit conversions
8	Word percentage problems
9	Word proportion problems
10	Word rate problems
11	Percent of increase and decrease problems
12	Geometry percent ratios
	Probability, Statistics, & Data Analysis
13	Calculation of the average of a list of whole numbers
14	Chart and table based calculations
15	Read statistical tables and graphs
16	Probability of an event and its complement
17	Calculating a data value given the mean and a set of numbers that contains the data value
18	Weighted average
19	Venn Diagrams (Counting)
20	Counting Techniques: Trees
21	Sample Space
22	Multiplication and Addition (And / Or) Probability and formulas
23	Mean, median and mode
24	Interpret, manipulate, analyze and make conclusions from graphs, tables, figures and diagrams
25	Conditional and joint probability
	Numbers, Concepts & Properties
26	Equivalent fractions
27	Simplifying fractions
28	One digit factors
29	Digit’s place value
30	Rounding
31	Ordering of decimals
32	Pattern identification
33	Absolute value
34	Prime numbers
35	Greatest common factor
36	Least common multiple
37	Ordering fractions
38	Numerical factors
39	Scientific notation
40	Squares and square roots
41	Positive integer exponents
42	Cubes and cube roots
43	Undefined expressions
44	Complex numbers
45	Prime factorizations
46	Even and odd numbers
47	Factors and multiples
48	Positive and negative number properties
49	Exponent Rules
50	Complex number multiplication
51	Number concept conclusions
52	Algebra concept conclusions
53	Expression relationships
54	Logarithms
55	Geometric sequences
56	Complex number properties
	Graphical Representations
57	Number lines – Coordinate Location
58	1^st Quadrant Coordinate Location
59	Cartesian Coordinate System
60	Slope Conceptualization
61	Distance on a number line
62	Number Line Inequality Representation
63	Slope Calculations and Determination
64	Linear graphs equation matching
65	Cartesian graphs interpretation and analysis
66	Midpoint of a line segment
67	Match inequality equations with graphs
68	Distance formula
69	Number lines and solution sets of inequalities
70	Determination of an equation of a line: points, perpendicular and parallel lines
71	Parabolas: vertex, direction, axis of symmetry, x-intercepts, y-intercepts
72	Circle: radius, center, area, sector length, circumference, chords
73	Quadratic inequalities: graphs and equations
74	Equation, function and graph matching
75	Algebraic conceptualization problems
76	Geometric conceptualization problems
77	Integrated algebraic and geometric conceptualization problems
78	Graphical analysis, interpretation and conclusions
	Properties of Plane Figures
79	Parallel lines, transversals and associated angles
80	Pythagorean Triples
81	Application of Isosceles triangles principles
82	Special triangles, side relationships
83	Multistep geometry problems
84	Relationships between angles, arcs and distances in a circle
	Measurements
85	Line length relations in a geometric shape or form
86	Perimeter of a polygon given all side lengths
87	Area of a rectangle given dimensions as whole numbers
88	Triangles: Area, perimeter, multistep problems, direct and indirect problems
89	Circle: Area, circumference
90	Perimeters of simple composite geometric figures
91	Integrated area, volume and perimeter relationships and calculations
92	Scaling factors
93	Area visualization of geometric shapes
	Functions
94	Quadratic functions (integer coefficients)
95	Polynomial functions
96	Trigonometric functions: sine, cosine, tangent (ratio of side lengths)
97	Composite functions: Expression development and evaluation
98	Trigonometric ratios application problems
99	Trigonometric identities
100	Trigonometric unit circle
101	Trigonometric function / graph matching

SAT 2016: Learning Point Math Checklist

2016-08-03T20:49:00.001-07:00

SAT MATHEMATICS

Learning Point Checklist

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PROBLEM SOLVING AND DATA ANALYSIS DOMAIN	Maximum and minimum values of functions	Linear function slope and relation to rate of change
Ratios, rates, proportional relationships, and units	Vertical shifting, horizontal shifting, scaling, asymptotes, end-behavior	Linear equations in two variable interpretation, analysis, application
Solve proportions in terms of scale factors	Linear, exponential, quadratic, polynomial, absolute value	System of linear equations: solve, interpret, analyze in context to academic and career applications.
Solve proportions through cross multiplication	Roots, zeros and x-intercepts	Solving for the equation of a line for a variety of different given conditions.
Derived units as found in chemistry, science, physics	Y-intercepts	System of equations, solving for solutions
Unit conversion: currency, measurement	PASSPORT TO ADVANCED MATH DOMAIN	Linear Inequalities: Interpretation, analyses and creation and solutions
Percentage calculations and application	Simplifying simple rational expressions;	ADDITIONAL TOPICS IN MATH DOMAIN
Scale drawings and proportions in natural and social sciences	Simplifying expressions with rational exponents and radicals;	Area and volume
Percent change and growth rate	Factoring polynomials.	Perimeter, area, surface area, and volume.
Distributions, measures of center and diffusion	Polynomial Operations: add, subtract, multiply	Scale Factors: perimeter, surface area volume
Graphical representation of data sets.	Nonlinear equations in one variable	Linear, Area and Volume Scale Factors
Graph, table and diagram interpretation, analysis and utilization	Systems of equations in two variables	Surface area and volume calculations with complex geometric shapes
Frequency tables, histograms, dot plots, and box plots.	Properties of operations	Lines, angles, and triangles
Calculate, compare, and interpret mean, median, and range.	Reasoning about equality to	Congruence and similarity of triangle theorem
Interpret standard deviation.	Quadratic equations: The Three Forms	Statements for proof of geometric theorems
Interpret distributions with different measures of center and spread, mean, standard deviation	Parabolas: Vertices, Roots, Factors	Angle scale factor relationships
Effect of outliers on mean and median.	Discriminant: none, one or two real solutions	Vertical angle theorem
Two-variable data: models and scatterplots	Solving one-variable rational or radical equations (extraneous solutions);	Triangle sum theorem
Line of best fit: slope, intercept, predictions	Solve factored one-variable polynomial equations	Transversals, angle relationships and parallel lines
Best fit modeling: Linear, Quadratic, and Exponential	Solve one-variable linear absolute value equations	Pythagorean theorem;
Compare linear and exponential growth.	Solve systems of linear and nonlinear equations in two variables	Right triangle trigonometry;
Probability and conditional probability	Graphical analysis of a system of linear equations	Special right triangles, 30, 45, 60
One- and two-way tables	Nonlinear equations in one variable	Similarity & sine, cosine, and tangent. calculations
Tree diagrams	Nonlinear equations in two variables	Solving a right triangle given an angle and a side
Area models	Solving an equation in two or more variables for a specific variable	Sine and cosine of complementary angles.
Relative frequency	Solving second degree equations in standard form or in vertex form through completing the square	Geometry of circles: Applications and properties, and theorems :radii, diameters, tangents, angles, arcs, arc lengths, and sector areas
Probabilities and probability formulas	Quadratic or exponential functions: create, use, solve, interpret in context	Radian measure and degree conversion
Conditional probabilities and formulas.	Modeling quadratic and exponential functions	Trigonometric ratios in the unit circle.
Population parameter inference from sample statistics and margin of error	Quadratic Standard Forms, Standard, Vertex, X-Intercept of a Parabola	Equation and graph of a circle
Estimation of population mean and proportion	Exponential decay forms, half-life, doubling time, end behavior	Completing the square for determining properties of a parabola
Margin of error: sample size relationship	HEART OF ALGEBRA DOMAIN	Completing a square determining circle parameters
Evaluating statistical claims: observational studies and experiments	Linear equations in one variable: constants, variables, factors, context.;	Advanced Math Terminology
Evidence for a causal relationship, random assignment	Linear functions: create, model use, interpret, analyze, solve in	Distance formula in problems related to circles.
Relations between populations and samples	Linear function control variables: horizontal, vertical and steepness translation	Complex numbers: add, subtract, multiply, divide

How to write an effective resume cover letter

2016-07-29T15:23:00.003-07:00

With an effective cover letter you will have a much better chance of getting your dream job. That's because an effective cover letter will make sure your resume won't be placed in the discard bin and will be read.

An effective cover letter includes a strong opening line that compels the recruiter to read on. It is short and to the the point. It also gives human resources and hiring managers something interesting or exciting to talk about.

An effective cover letter tells something about your personality that appeals to the hiring manager. It makes them curious and gives them a strong interest in finding out more about you.

Because cover letters are often tailored specifically to the company's values and needs, you almost always need to research the company and the hiring managers. This means you must budget your time and seriously critique your cover letter from a specific hiring manager's point of view.

About BookMarkTutoring.................BookMarkTutoring.com provides academic, business and career consulting services. These include resume writing services and instruction. BookMark also provides one-on-one instruction for a wide range of academic subject from grade school to graduate school.

Summer Art Classes: Learn How to Draw and Create .........BookmarkTutoring.com ,,,,,,, Santa Rosa

2016-05-20T18:34:00.003-07:00

Summer Time is time for fun learning at BookMarkTutoring.com..........

At BookMark you can learn what you need to know to design your own coloring cards, coloring books and even your own houses and clothes.

The beautiful illustration on the left is another BookMark Original. Titled Goddess of Sound, it combines architecture and fashion into a composition that sends messages throughout the universe.

At BookMarkTutoring.com we offer personalized drawing instruction at your home, in the park, the local coffee shop or even online.

But that's not all, we are one of a very few tutoring companies that use art as a tool to teach math. And use math to teach art.

At BookMark we developed the mathematical paintbrush. With the mathematical paintbrushes on our infinity drawing machine, we show how you can use the math functions you learn in school to create master pieces. The parabola brush, the line brush, the exponent brush are just a few of the math strokes you will learn in our Mathematics of Art lessons.

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Contact: Mark C. Stansberry
Tel: (707)235-4095
Email: mark.c.stansberry@gmail.com

House Plants for Healthy Homes and Healthy Businesses

2016-01-04T14:05:00.001-08:00

Mark C.Stansberry
Email: mark.c.stansberry@gmail.com
Posted: 2016, January 4

House plants can be categorized into 6 distinct functional room categories:

1) Bedroom Plants
2) Bathroom Plants
3) Living Room Plants
4) Fireplace Plants
5) Kitchen Plants
6) Business Plants

Different types of plants are best for different rooms and conditions. One reason is that different plants produce oxygen at different times and in different amounts. Another reason is that different plants also have different ant- bacterial properties. This makes some plants better for the kitchen or better for the bathroom.

Businesses have unique air quality needs for their environment. A business such as a crowded coffee shop needs plants that produce high amounts of oxygen as well as removes bacteria and pollutants from the air.

Many studies reveal that house plants increase productivity, reduce the length of colds, and increase energy levels. This is not surprising. Increased oxygen levels in the home or business setting will increase oxygen levels in humans and animals. Increased oxygen levels help the body remove toxins and metabolize nutrients.

For more information on growing plants for your home or business contact www.bookmarktutoring.com. BookMarkTutoring provides instruction and lessons on how to grow plants for your home or office. BookMark can show you what plants to grow to produce a healthy and productive environment for your home or office.

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ACT Math Learning Points ..

SAT 2016: Learning Point Math Checklist

How to write an effective resume cover letter

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