The circuit diagram given below shows 250 mW audio amplifier. This circuit contains three transistors Q1 (BC547), Q2 (BC327), Q3 (BC337) as central components. Transistor Q1 in this circuit acts as preamplifier where as Q2 and Q3 are output pairs. Transistors Q2 and Q3 are complementary transistors. Decoupling of DC from audio source is done by the capacitor C1 (10 uF). Resistor R2 (82K) is used in this circuit to provide better stability for the amplifier. Variable resistor POT R5 (10K) is used as volume control element.
The circuit is powered using a 9V DC supply. The value of impedance of speaker K1 can be 8 ohm. In order to get the optimum output from the circuit, decouple input and output grounds properly.
- Use a Vero board to assemble components for this circuit.
- This type of amplifiers finds applications in small radio sets and in high power amplifiers as preamplifier.