







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.









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