This is the circuit design of Class-D power audio amplifier using IC MD7120 as MOSFET driver. The MD7120 used to drive four N- channel MOSFET Transistors that operate on both sides of the H-bridge switches. It consists of controller Logic circuits, level translators, two bootstrap powered high-side Gate drivers, two VDD powered low-side Gate drivers, and over current protection circuits (without using a current-sensing resistor). The over current protection thresholds for both the high and low side are separately resistor-programmable.

The MD7120 is designed to drive 3.0A, fast switching MOSFETs with well-matched input to output propagation delay between the high-side and the low-side, as well as from channel A to channel B. The circuit uses the direct-coupling method in its internal level translators, from logic inputs to the gates of the N-channel power MOSFETs.

The MD7120 input logic voltage can be set to any voltage between 1.8 and 5.0V by connecting the EN pin H logic voltage level at the same level as the switching control inputs. The internal EN pin circuit will compute the logic threshold when it is high and disable the output when it is low. The MD7120 is packaged in a low inductance, thermally-resistant, 32-Lead, 7.00×7.00mm QFN package. With a proper PCB heatsink, the IC power dissipation is about 3.5W.

The high-side power MOSFET drains can be connected to a high voltage power supply, while the bottom N-channel MOSFET source is grounded if it is connected to a single high voltage power supply. In that case, digital audio signal processor IC outputs can be directly connected to the MD7120 input with ground-reference level with no level shifter required. However, then the speaker or the single channel output reference cannot be connected to ground.

Download the Application Note of this circuit design here:

MD7120 Class-D Audio Amplifier Design

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Active Antenna Amplifier Notes

Active antennas are any antennas with integrated signal amplifiers built right into the unit. While, passive antennas are antennas that have no amplification stages.

An active antenna is a passive antenna that simply includes an onboard amplifier. There is no difference between the antenna element of an active or passive antenna of the same type; the only difference is whether an amplifier is included.

Active antennas can be used for both receiving and transmitting applications, but they are most often seen as receiving antennas. When used to receive signal, the integrated amp boosts the RF picked up by the antenna and allows much longer remote cable runs.

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400 Watt 70 Volt Amplifier Part List

Transistors

• 2SC5200 or equivalent MJL21194 : 8
• 2SD718 or equivalent C5198 : 1
• 2SB688 or equivalent A1941 : 1
• 2SC2229 or 2SC2230 : 2
• A1015 or A872 : 2
• TIP42 : 1

Capacitors

• 6800uF/80V or 10000uF/80V Electrolytic Capacitor : 2
• 100uF/80V Electrolytic Capacitor : 2
• 2.2uF/50V Electrolytic Capacitor : 1
• 10pF ceramic capacitor : 2
• 470pF (471) ceramic capacitor : 2

Resistors

• 0.33 ohm 5W : 8
• 4.7 ohm 1W : 8
• 100 ohm 1W resistors (brown, black, brown) : 2
• 33 ohm 1/4W (orange, orange, black) : 1
• 150 ohm resistors at 1/4W (brown, green, brown) : 3
• 10K ohm 1/4W Resistor (Brown, Black, Orange) : 1
• 1K ohm 1/4W Resistor (Brown, Black, Purple) : 1
• 4.7K ohm 1W (yellow, violet, purple) : 1
• 68K ohm 1/4W (blue, green, orange) : 2
• 33K ohm to 1/4W (orange, orange, orange) : 1
• 3.3K ohm 1/4W resistors (orange, white, purple) : 2

Diodes

• Diode bridge of 15 amps or greater : 1
• Diodes 1N4007 : 3
• Zener Diode of 18 volts or 24 volts : 1

Others

• Fuse holder and fuse of 3 amperes.
• Transformer for the amplifier should be 55 + 55 volts AC with a current of at least 10 amps.

400 Watt 70 Volt Amplifier PCB Layout Design

This is the PCB layout for 400w pawer audio amplifier. The power supply is already included in the printed circuit board although in the schematic design, the power supply was not included. Please refer to the connection image in the end of this post.

400 Watt 70 Volt Amplifier Top PCB Design and Component Layout

400W Power Amplifier Connection

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This is the circuit diagram of 150W power amplifier which built using power transistors. The circuit above is essentially a mono channel circuit. To make it into a stereo channel, you have to build the two identical circuits. 150W is high enough for the audio system in a small field or in the hall/meetinghouse.

150W Power Amplifier Note

To maintain performance remains excellent and prevent damage to the power transistor caused by excessive heat, then you must install the heatsink on the transistor Q7 to Q12.

On 150W power amplifier circuit schematic above is included the simple power supply circuit that very easy to built. Transformer to use is 3A minimum for mono applications, and 5A minimum for stereo applications. For better performance, maybe you could try using a regulated power supply that is certainly capable of providing a large current and voltage as needed by this power amplifier circuit.

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This is the circuit design of 1000W stereo audio amplifier. It is a very good design to assemble, easy to build from your board to the acquisition of components, the output transistors are the COMPLEMENTAR 2SC5200 and 2SA1943 relatively cheap and with very good result. In the power supply module we have 6 capacitors 4700uF/80v or more and one 50A bridge rectifier diode, this design can be in versions mono (500 Watts) or stereo (1000 Watts), if it is to mount it in the stereo version it is good to use a transformer of at least 8 Amperes and the voltage in both versions has to be 50v + 50v with central bypass, this transformer can be toroidal or ordinary.

Stereo Audio Amplifier Part Lists

Transistors

10 Transistors 2SC5200
10 Transistors 2SA1943
4 Transistors C2073
4 Transistors A940

Resistors

20 Resistors of 2.2 ohms 1/2W
20 Resistors of 0.33 ohms 5W
4 Resistors of 10 ohms 1W
4 Resistors of 100 ohms 1W
4 Resistors of 5.6K 1W
10 Resistors of 100 ohms 1/4W
4 Resistors of 330 ohms 1/4W
4 Resistors of 1K 1/4W
4 Resistors of 18K 1/4W
2 Resistors of 33K 1/4W
2 Resistors of 56K 1/4W

Capacitors

6 Capacitors of 4700uF/80V or more
6 Capacitors of 100uF/50V
2 Capacitors of 1uF/50V
2 Capacitors of 100pF ceramic
2 Capacitors of 15pF ceramic
4 Capacitors of 330pF ceramic
4 Capacitors of 680pF ceramic
4 Capacitors of 220 pF to ceramic
2 Capacitors of 0.1uF (104) / 250V polyester
5 Capacitors of 0.1uF (104) / 100V polyester

Miscellaneous

2 Integrated Circuits TL071 or UA741
4 15-volt to 1W zener diodes
4 Diodes 1N4007
1 Diode bridge of 35 amps or more. Best if it is 50 Amp
2 Small 2-pin GP connectors
2 large 3-pin Molex connectors
2 large 6-pin Molex connectors
1 50vx50v transformer, or up to 55x55V AC with current 15 amps minimum (stereo version)
2 Sockets for 8-pin integrated
4 sinks of 22 x 10 x 2.5 centimeters
24 mica insulation

1000W Stereo Audio Amplifier PCB Design

Power Supply for 1000W Stereo Audio Amplifier

1000W Stereo Audio Amplifier Stereo Channel Connection

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Tone Control for 150W Car Audio Amplifier

The tone control circuit build based on IC LF353 In stereo mode, we shall have the action of eight loudspeakers which are going to create a very important sound pressure.

Tone Control Scheme

Tone Control PCB Design

150W Car Power Amplifier

The power amplifier is built based single LA47536 power IC for each channel. For stereo channel you need two similar circuit for each modul (tone control and power amplifier)

The LA47536 is a 4-channel BTL power amplifier IC developed for use in car audio systems. The output stage features

• A pure complimentary structure that uses V-PNP transistors on the high side and NPN transistors on the low side to provide high power and superb audio quality.
• The LA47536 includes almost all the functions required for car audio use, including a standby switch, a muting function, and each protection circuit. It also provides a self-diagnosis function (output offset detection).

Power Amplifier Scheme

Power Amplifier PCB Design

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This is the circuit design of 21W class AB audio amplifier uses power transistors as the main part. It is a simple design, and simple to set up. Set the 10k trimmer to about half way and the 470 ohm trimmer to 0 resistance. Power up and set the quiescent current to 30mA by trimming the 470 ohm trimmer. Once done, measure the offset voltage. Trim the 10k so that between -30 and 30mV is measured. The amplifier should now be able to pump out just over 21W.

Technical Data:

Frequency response: 2Hz – 17kHz flat
THD: Once again, very low (I haven’t measured it yet). It won’t be audible
Gain: 29.87dB (600mV for 21W into 8 ohms)

The gain can be modified by changing the 100k feedback resistor to a 470k resistor and the 10k in series with the input to a 33k. This will increase the input impedance significantly and the new gain will be 21.58dB (~1.6V input for 21W into 8 ohms). This suits my application for the amp. Just remember that changing these resistors will change the output offset voltage, so if you’re going to experiment by changing the feedback loop, do it with a cheap, single driver speaker if you’re experimenting with a speaker connected. Also readjust the offset and quiescent current!

Power Supply for 21W Class AB audio Amplifier Circuit

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4 Channel Amplifier Parts List

D1-D4: 1N4001 (4)
C1,C20: 1000u CAP (2)
C2,C11: 47u CAP (2)
C3,C5,C7,C8,C12,C14,C16,C17,C21,C22: 0.1u CAP (10)
C4,C6,C13,C15: 10u CAP (4)
C9,C10,C18,C19: 2200u CAP (4)
R1,R4,R9,R12: 1M RESISTOR (4)
R2,R6,R10,R14: 100k RESISTOR (4)
R3,R5,R11,R13: 1k RESISTOR (4)
R7,R8,R15,R16: 2R7 RESISTOR (4)
IC1: 7812 (1)
IC2,IC3: LM1877N (2)
SPK1,SPK2,SPK3,SPK4: 8R 2 Watt speakers (4)

4 Channel Amplifier Notes

The overall gain is controlled by the ratio R14/R13 and R6/R5. Used by small Hi-Fi speakers, the volume was too loud for small room so you may reduce R14 and R6 to 33k. The Zobel network formed by R7, C7, R8, C8, R15, C16, R16, C17 prevents instability which can happen with long speaker wires. The input impedance is high, 1M and if very long input cables are present could pick up noise. Screened cable should be used, in my case I used 10k resistors between points A & C, B & C, D & F, E & F. This provides a DC path to ground and higher noise immunity. If instability does occur, then you will notice sound distortion and the LM1877N will become hot to touch.

4 Channel Amplifier circuit source: zen22142.zen.co.uk

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Below is the 600W MOSFET power amplifier circuit design and the power supply circuit designed for this power amplifier. PCB layout design for the power amplifier and it’s power supply is provided.

600W MOSFET Power Amplifier PCB Design

Power Supply Circuit Design

Schematic Diagram:

PCB Layout:

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Here the circuit design for DIY guitar transistor preamp. It consists of a circuit of two transistors and four controls that can be vary the level of the treble, bass, gain, and total salidad circuit (volume). It can be used as buffer at the beginning of a chain of effects. Or combine it with the Marshal Guvernor and a power to put together a cute amplifier.

The circuit working with 9v dc power supply or battery.

Guitar Preamp Components list:

Nonpolar Capacitors

• 0.01uF
• 0.1uf
• 4700pF
• 0.047pf

Electrolytic Capacitors

• 1uf x 2
• 1uf x 2 (Tantalum)

Semiconductors

• 2N5089 (NPN or other) x 2

Resistors

• 1M x 2
• 47k x 2
• 2.2k x 2
• 100k x 2
• 4.7k
• 22k
• 1k

Potentiometers

• 250 Kohm linear x 2
• 250 Kohm log
• 10 Kohm linear

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