Single Transistor Amplifier

This is an interesting practical project which even a novice can build! It is a simple single transistor amplifier circuit which can be powered by 1.5V to 5V. This project uses few components which you can easily get even from a dead circuit.

The circuit uses a single NPN bipolar junction transistor (BJT) and can drive a 0.2W to 5W Speaker of 3 – 4Ω impedance. The input voltages range from 1.5V from a single cell to 5V DC single supply.


Below are the components you will need for this simple single transistor amplifier project. You can find these components even in a dead electronic panel or circuit board.

  1. NPN Bipolar Junction Transistor (BJT)
    • C2655 (1) or any NPN BJT
  1. Fixed Resistor
    • 22KΩ (1)
  1. Polarized Capacitor
    • 10uF (1)
  1. 1.5V to 5V Cell (2)
  2. 3Ω impedance, 0.2W to 15W Speaker

Single Transistor Amplifier

If you have successfully constructed the circuit, you’d probably notice some distortions in the sound quality. But don’t worry, there is still simple modification you can do to improve the quality. Connect a resistor with a low resistance like 3Ω to 12Ω in series from the emitter (E) of the transistor to the ground (0V) supply to improve the output sound quality.

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