Class AB Transistor Power Amplifier Circuit Diagram

Class AB Transistor Audio Power Amplifier Circuit

Discrete Class AB Transistor Audio Power Amplifier Circuit Diagram

This is a class AB transistor power amplifier. It is a simple amplifier to build, uses standard parts and is stable and reliable.  The entire circuit utilizes commonly available components and may be simply built over a general-purpose board. But this amplifier has very good sound quality.


Class AB Transistor  Power Amplifier Circuit schematic

There are eleven transistors, including four in the output stage. Q1 and Q2 transistor must be between 3 and 5  amperes power transistors. Q4 and Q5 must be between 100mA and 500mA driver transistors. Other transistors are 10mA small driver transistors. Q1, Q4 and Q2, Q5 are complementary pairs, they make complementary darlington pairs.

R1 1.5KΩ ¼W
R2 150Ω ¼W
R3 1KΩ ¼W
R4 0.22Ω 2W
R5 0.22Ω 2W
R6 39KΩ ¼W
R7 1KΩ ¼W
R8 120Ω ¼W
R9 6.8KΩ ¼W
R10 6.8KΩ ¼W
R11 47KΩ ¼W
R12 47KΩ ¼W
R13 2.2KΩ ¼W
R14 180KΩ ¼W
R15 18KΩ ¼W
C1 22pF Ceramic
C2 4.7µF 16V
C3  1000µF 25V
C4 100µF 25V
D1 1N4148
D2 1N4148
 Q1  2SD313
 Q2  2SB507
 Q3  2SA733
 Q4  2SB560
 Q5  2SD400
 Q6, Q7, Q8, Q9, Q10  2SA733
 Q11  2SD400

Power output of the amplifier

Supply voltage (Vs) = 20V
 Speaker impedance (R) = 4Ω
 Peak to peak voltage (Vpp) = 20-2 =18V
 Peak voltage = 9V
 Maximum output (Pmax) = 9V2/2R
= 81/8
= 10W

10W is much enough for the day today home usage.

Amplification of this amplifier (A)

A = R6/R13+1
= 39KΩ/2.2KΩ+1
= 18

Volume control can be added to the circuit by connecting a 10KΩ  POT in series to the input of the amplifier.

Q1 and Q2 must be kept sufficiently cool, so it is mounted on a suitable heat sink. If you used single heat sink please use insulation between transistors and heat sink.

Class AB Transistor Audio Power Amplifier Circuit Discrete Class AB Transistor Audio Power Amplifier

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15 comments on “Class AB Transistor Power Amplifier Circuit Diagram
  1. Jack Smith says:

    This is a neat and simple circuit. It should be easy to build and will work great.

  2. karna says:


  3. yokeswaran says:


  4. Sidiney Leonidas says:

    (Portuguese From Brazil) que maravilha esses progetos eu realmente amei são fáceis e praticos

  5. Ricardo says:

    Sidiney Leonidas :
    (Portuguese From Brazil) que maravilha esses progetos eu realmente amei são fáceis e praticos

    Nós do Brasil escrevemos pro”G”eto com “J”! Enfim, o projeto é sim muito bom. Vou montar e avaliar e comparar com o TEA2025B, que é o padrão para caixas de computador. O objetivo é construir um amplificador básico com ótimas respostas para o dia-a-dia na frente do computador.

  6. shawn says:

    i just want to ask,, where did they got the value of 2 in solving the voltage peak to peak???

  7. USAMA JAVAID says:

    i am using MS2475 transistor in my design but unfortunately this transistor is not easily any one can tell me about its replacement.i am designing my amplifier in ADS .any one know any thing about it .contact me .thanks

  8. Bubble says:

    Nice, very nice!

  9. h says:

    thank you very much

  10. is it ok to use 5watts in a resistor .22ohm rather than a 2 watss resistor?

  11. auxtics says:

    Hi guys,
    If you are beginner and want to build your own amplifier circuit then visit this link to watch this video and have your complete kit for building your great tda2030a / tda2050 based stereo amplifier.

  12. Yash says:

    These are the requirements: a minimum of 8W RMS power to 8Ω speakers with a maximum of 1% second harmonic distortion and 0.2% third harmonic distortion. Single chip integrated IC amplifiers are not allowed. BJT and MOSFETs in class A, AB, D or circlotron topology are recommended.

    Is this circuit suitable for my requirements and is there any simpler circuit possible?

  13. Allan says:

    I’m building up this circuit as a hobby. My wish is to build up the circuit in a pcb.
    Does any one mind sending the pcb layout to me?

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