# 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.

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.

 PART LIST 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 LS1 4Ω 20W SPEAKER

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.

Please send your ideas, which are very important for our success…

###### 24 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:

thanks

3. yokeswaran says:

oh!awesome!

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. aru says:

nice

8. USAMA JAVAID says:

i am using MS2475 transistor in my design but unfortunately this transistor is not easily available.so 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

9. Bubble says:

Nice, very nice!

Very very nice

10. h says:

thank you very much

11. zeeshan says:

AS A PRACTICAL

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

13. 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.

14. 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?

15. 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?

16. hassan says:

Can I use 9v battery to operate this circuit

17. Celestine says:

I am working on my degree project,and I need assistance on performance evaluation of 100w audio amplifier,
Thanks.

18. Muhammad Qamar Ilyas says:

Can any one tell me the replacement of B560 and B507 transistors?

19. vamsi says:

can you tell me the advantages and give me the real time applications of this thing. how does this differ from other audio amplifiers. please reply asap

20. Nimita says:

M not getting the components of the ckt in proteus plzzz…tell me another tool so that i can easily get the components

21. ms says:

I made this. But gain was 1.2~1.5V/V. I think you need to check the components.

22. Cesar del Aguila G says:

This is a simple and easy to build amplifier circuit with good results, and single supply!

By the way… yes the output are complementary pairs, but are not Darlington, are Sziklai arrangement.

CesarIII

23. Elbert Abrea says:

What thus +12…20V means??? voltage from 12V to 20V?? and also what I can put to that INPUT??? Is it okay to connect it with a microphone coil??? Thank yOU…

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