Introduction: Small Transistor Audio Amplifier

About: Free electronic circuit design

For some simple applications such as toys, intercom, or small gadgets, there is sometimes a need for small, simple, low cost, or low voltage solution of power amplifier circuit. For this requirement, high fidelity is rarely needed.

Step 1: Prepare the Components

  1. Resistor
    1. R1 .. 1K
    2. R2 .. 4K7
    3. R3 .. 4K7
    4. R4 .. 6K8
  2. Electrolytic Capacitor (ELCO)
    1. C1 .. 10uF/25V
    2. C2 .. 220uF/25V
    3. C3 .. 100uF/25V
  3. Dioide
    1. D1 .. 1N4148
    2. D2 .. 1N4148
  4. Transistor
    1. TR1 .. 2N3904
    2. TR2 .. 2N3906
    3. TR3 .. 2N3904
  5. Misc
    1. Battery or Power Adapter (3V)
    2. Small Loudspeaker (8 Ohm)
    3. Bread board (for experiment only) or matrix board (for usable stuff)

The capacitor voltage is specified at 25V in the schematic, but actually you can any voltage rating from 6.3V or higher.

Step 2: Assemble the Compoents

Assemble the prepared components in the breadboard or in the matrix board. Use breadboard for experiment only, and use a matrix board if you want to use it in your gadget.

Step 3: Connect the Power Supply and the Loudspeaker, Ready to Use

Now you can use the amplifier and connect the input to the signal source see the demo video on the Youtube channel and learn how it works and how to modify the circuit here: Small 3-Transistor Audio Amplifier.