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,Q4andQ2,Q5arecomplementarypairs,theymakecomplementarydarlington 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.
Arcadia Lis
2017/2/6 16:23:55
Marvelous posting.