Class A amplifier circuits

These are simple Class A amplifier circuit. First circuit I used main part electronic is transistor only.The main power transistor i used TIP41 or TIP31 or C1061 or MJE3055 and next part is TIP42 (PNP) or TIP32 or A761. It is have power output 20W at 8ohm. and used volte of supply 22V to 28V at 4A.
Detail more please read in image.

The Clipping Power Amplifier Circuit

The Clipping Power Amplifier Circuit

Here is the 5 watts really class A amplifier using NE5532 and MJ2955 as based. This is best of quality sound.

We used popularly the many type of power amplifier. For example: Class A, Class B, Class AB etc. The Class A amplifier is the best of quality sound.

But the class A to the output power is low, just 20% only. When compared with a loss of power or consumption ratio approximately 5 times of the output power.

So we have a problem with the heat. Although there is no ?the input audio. However, despite the low wattage, it also provides crystal clear sound quality than class B and class AB.

How circuit works
The principle of the class A amplifier is IC1 will increase a positive halfcycle signal. Then, this signal will flow through to a capacitor C2 into both transistors Q1 and Q3 as darlington compound, to increase the audio signal up.

5 watts Class A amplifier using NE5532 and MJ2955

And the negative halfcycle signal will through C3. Then, the signal will be increased by both Q2 and Q4. Which is also the darlington.

Next, the output positive halfcycle signal will come out to lead E of Q3, and the negative halfcycle signal will through lead E of Q4.

Then, the signal will flow through R10 and R11, to protect output short circuit. Next, out to the speaker that output no more than 5 watts.

The diode D1-D4 acts as the rectifier to DC voltage to bias Q1 and Q2, and VR1 adjusted bias current is steady in working that, by Q1-Q4 will be screw to the heatsink. Especially in Q3 and Q4.

The heatsink is large because the circuit has lost high power.

The parts you will need
R1__________68K ¼ W
R2__________2.7K ¼ W
R3__________39K ¼ W
R4, R5_______1K¼ W
R6, R7_______1.5K ¼ W
R8, R9_______100 ohms ¼ W
R10, R11_____0.1 ohms 3W
VR1________470 ohms__Linear Potentiometer
C1__________Ceramic capacitors 0.82uF 50V or 1uF 50V
C2, C3______100uF 16V Electrolytic
Semiconductors and others
D1-D4______1N4003____1A 300V__Silicon Diode
Q1_________BD139 ___80V 1.5A NPN Transistor
Q2_________BD140 ___80V 1.5A PNP Transistor
Q3_________2N3055___100V, 15A, NPN transistor
Q4_________MJ2955___100V, 15A, PNP transistor
IC1_________NE5532__OP Amp Dual General Purpose ±20 Volt 8-Pin DIP
SP1_________Speaker 8 ohms 5W
T1_________6V-0-6V/ 5A_____Dual DC power supply
T2_______18V-0-18V, 1A ____Dual DC power supply

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capacitors goes boom twice while making this.
and seems it destroyed some of the transistors. damn.


why you have used the TIP 41 and TIP 42 transistors?they are complementary transistors and this mechanism is push-pull mechanism and push-pull mechanism is use in class B type power why you have use this push-pull mechanism in class a amplifier??


but anyhow its working well,,,giving much amplification,,


why complementary transistors have used?TIP 41 and TIP 42 are npn and pnp transistors and this mechanism is use in class B amplifiers,,why you have used in class A?

Debbie Austin

I’ll already try this Power Amplifier Class A by Transistor circuit, and i heard humming sound when the input is connected. All I have to do is to change the transformer from 3 amperes to 6 amperes. and absolutely no heard humming ever after I changed.


i already try this circuit. and it’s work… all caps use 50volt. the transformer 7 ampere.. need big heat sink… remember this iis A class amps

Keith Gaston

Even you have high current of power supply you can never feel the full specification of that amp, the most important of amplifier is regulated power supply.


i know this thread is very old but here it goes.
we tried this circuit and got this issues.

bc337 always burns up.
current flows through the input (we got electrecuted when power suppy is plugged through the input. input from iphone 4)

power supply we used is a laptop adapter 19v
we used a different trans for bc179(any other recommendation?)
if power supply is connected without any input connected in the first place, bc337 burns immediately. where can i put a volume control


the amplification is very good btw and I almost don’t hear any noise/distortion that’s why i like to make it. plus it’s discrete


we tried ciruit but got nothing out no humm or anything is value at r 7 .68 ohm got 7 volts at c5 but nothing at speaker output


all these amplifier circuits are not working, at least i’ve tried two now and the two circuits are nt working for me, pls i need a functioning circuit of abt 12v to 24v


the thing oscillates and heats up and lot of distortion weak fake btw if you split the power supply and ground the speaker – and the input ground to the ground it outputs 50 to 200mv in the input but still doesen’t work if you want a real amp visit:

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