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.


AB Transistor Audio Power Amplifier Circuit Diagram

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.