2n3055 Audio Amp — Schematic

They boost the signal enough to "drive" the heavy-duty 2N3055s.

potentiometer is usually placed here to adjust (to prevent crossover distortion). Output Stage (The 2N3055s) 2n3055 Audio Amp Schematic

A small-signal transistor (like a BC547 or 2N2222) acts as the initial pre-amp/differential pair. The BD139 and BD140 transistors form a complementary pair. They boost the signal enough to "drive" the

This stabilizes the gain and reduces total harmonic distortion (THD). Safety & Build Tips The BD139 and BD140 transistors form a complementary pair

This design typically follows a push-pull architecture. It uses two 2N3055 transistors as the final power stage to drive an 8-ohm speaker. Key Components Power Transistors: 2x 2N3055 (NPN) Driver Transistors: BD139 (NPN) and BD140 (PNP) Voltage: Dual rail supply ( ±35Vplus or minus 35 cap V Power Output: ~50 Watts into 8 Ohms Step-by-Step Connection Logic Input Stage The audio signal enters through a electrolytic coupling capacitor.

as these transistors generate significant heat during operation. emitter resistors to provide thermal stability. Feedback Loop A resistor (typically ) connects the output back to the input stage.

💡 Use mica insulators and thermal grease when mounting 2N3055s to a shared metal heatsink. Fusing: Place 2A fuses on both the +Vpositive cap V −Vnegative cap V rails to protect the transistors from shorts.