This miniature audio amplifier delivers up to 250mW and can be used like a final stage audio amplifier for radio sets. The schematic is very simple: one BC547 transistor controls a balanced power amplifier built with BC337 and BC327. The total amplification is around 15x and is determined by R1, R3 and P1. The input sensitivity is 95mV and the total current consumption is 180mA.

Small audio amplifier circuit diagram

miniature audio amplifier circuit schematic