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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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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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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This is the circuit design of Mosfet power amplifier 5200W RMS, the schematic is for single channel. The circuit uses 16x IRFP250 to gain 5200W RMS power output at 2 ohms load.

To feed this circuit , you will need 150 volts dual polarity (symmetrical) power supply of course with very high DC current.

If you want to build this amplifier circuit, you should be careful and try to find some reference about this kind of circuit since it uses high DC voltage and high DC curent and of course expensive loudspeaker. I haven’t build this circuit yet, try this circuit with your own risk.

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This the circuit diagram of 260W power audio amplifier capable of delivering up to 260W RMS at 8 Ohms load. The signal level of 1 VPP standard amplitude is input to a differential stage composed of BC556C Transistor. Then the signal is input to the post-formed by complementary transistors in order to achieve the desired power.

All transistors except BC556C, should be mounted on a suitable heatsink to prevent overheating. It would also be ideal to mount the plate in a metal cabinet to prevent unwanted noise.

This power amplifier uses complementary transistors in order to achieve the desired power. It is powered by a dual polarity power supply of +/- 45V and consumes 4 amperes, the circuit diagram provided. ALL diodes labeled A, B and C in the amplifier scheme diagram are 1N4001 and also be mounted on the heat sink but with silicone grease. The entry should be 1 Volt to deliver full power.

The power supply can not be regulated, but the filter must be very good to avoid “hum” in the speakers.
In this case the transformer has a secondary with midpoint of 32V / 0V / 32V (center tap). For mono configuration must have a current of 4A, 8A stereo. The diodes must be at least 100V by 6A (mono) to 12A 100V (stereo), you may use bridge amplifier for the rectifier diode. The capacitor should be minimum of 4700μF x 63V each.

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Above schematic diagram is 1 Watt stereo audio amplifier based IC KA2209 can be used for small electronic device such as radio, smartphone, tablets or other gadgets which require little sound amplification

This is the text book circuit for this IC in stereo mode. It is ideal for battery powered operation. Power output depends critically on speaker resistance & supply voltage. At 3V into 4 ohm speakers the power is 0.1W. At 6V into 4 ohm speakers it is 0.65W. At 9V it is over 1W.

This stereo amplifier module uses the Samsung KA2209 8-pin IC. This IC can be replaced with TDA2822. It is designed for portable casette players & radios. It has a wide operating supply voltage of 1.8V to 9V so it is suitable for battery operation.

Components List:

R3, R4 : 4R7 yellow violet gold
R1, R2 : 10K brown black orange
C1 : 10uF mini
C4, C5 : 100uF/25V electrolytic capacitor
C2, C3 : 470uF/16V electrolytic capacitor
C6, C7 : 100nF box capacitor
IC KA2209
8 pin IC socket

Download the circuit manual:

CK704 - 1W Stereo Amplifier Module

1 file(s) 179.22 KB

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