12 Watt Amplifier Based Transistors

This amplifier circuit is very easy to make with inexpensive costs. Consists of an op-amp IC combined with four transistors. The type UA741 IC is powerful enough for middle-class audio use to produce the desired reinforcement. The four final transistors are arranged in darlington to produce high hFe gain.

The Op-amp IC is supplied with a 12VDC power supply that has been lowered through resistors R5 and R6. Because IC 741 input current is determined by the input signal level, the voltages R5 and R6 must be proportional to the input signal. Although simple, this amplifier chain is capable of producing 12 Watts of power at a 4-ohm loudspeaker load.

12 watt amplifier based transistors

Part list:

IC : UA741
Q1 : BC178
Q2 : 2N6107
Q3 : AC108
Q4 : 2N5294
R1 : 10k
R2 : 270k
R3, R4 : 47k
R5, R6 : 1k
C1 : 50pF
C2 : 0,01uF
SP : Speaker 4 ohm

In order for this amplifier to be free from noise due to unstable power supply, the power supply must be filtered properly such as an IC regulator equipped with filter capacitors. This amplifier requires a 12VDC symmetrical power supply of 2 Amperes.