Wednesday, September 24, 2014

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
R11.5KΩ ¼W
R2150Ω ¼W
R31KΩ ¼W
R40.22Ω 2W
R50.22Ω 2W
R639KΩ ¼W
R71KΩ ¼W
R8120Ω ¼W
R96.8KΩ ¼W
R106.8KΩ ¼W
R1147KΩ ¼W
R1247KΩ ¼W
R132.2KΩ ¼W
R14180KΩ ¼W
R1518KΩ ¼W
C122pF Ceramic
C24.7µF 16V
C3 1000µF 25V
C4100µF 25V
D11N4148
D21N4148
 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.