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.

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.

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


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12 comments on “Class AB Transistor Power Amplifier Circuit Diagram
  1. h says:

    thank you very much

  2. Bubble says:

    Nice, very nice!

  3. 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

  4. shawn says:

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

  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. Sidiney Leonidas says:

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

  7. yokeswaran says:

    oh!awesome!

  8. karna says:

    thanks

  9. Jack Smith says:

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

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