Here is a very simple three transistor audio amplifier circuit that can deliver 250mW to a 8Ohm speaker. Complementary transistors BC337 and BC227 (Q3 and Q2) are used as the output pair. Transistor Q1 (BC 547) acts as the preamplifier.POT R5 can be used as a volume control. Capacitor C1 decouples the DC from the audio source. Resistor R2 ensures better stability for the amplifier.This amplifier is very suitable for application in small radio sets and as a preamplifier in high power audio amplifiers.
- The circuit can be powered from 9V DC.
- Assemble the circuit on a Vero board.
- K1 can be an 8 Ohm speaker.
- For better performance, properly decouple the input and output grounds.
- POT R5 can be used for adjusting volume.