Simple Single Transistor Audio Amplifier Circuit

If you want to built simple audio amplifier without messy components then you can construct simple single transistor audio amplifier circuit using BC547 and Resistor, Capacitor. This circuit can drive 8 ohm loud speaker and produce considerable sound. Apply 9 Volt DC supply for better result.

Two types of single transistor audio amplifier circuit designed with BC 547 transistor, here first one is for to amplify direct audio signal and another one is for to amplify audio signal from condenser MIC as a preamplifier.

Circuit Diagram


Components Required

  1. Transistor BC 547 (NPN) =2
  2. Resistor 2KΩ = 2
  3. Resistor 10KΩ, 2.2KΩ each one
  4. Electrolytic Capacitor 47µF/16V
  5. Electrolytic Capacitor 1µF/16V = 2
  6. Loud Speaker
  7. 9V Battery

Construction & Working

To construct Amplifier circuit start with Transistor BC 547 and Connect proper bias to Collector, Base and Emitter terminals, For the first circuit Loud speaker is directly connected to the transistor collector terminal and for Preamplifier circuit speaker connected through coupling capacitor C2.

Input Audio signal for the first circuit is applied to the BC 547 base through Capacitor C1 (47µF) and Collector coupled Resistor R1 hence the enough Audio signal and bias above cutoff voltage is constantly present at Base terminal of BC 547 and amplify the input signal near to peak Vcc.

Input Audio signal for the second circuit is applied from the Condenser MIC and it may raw electric audio signal with distortion and noise in order to improve the audio signal we need to filter and amplify the input signal. To give strength to the MIC signal R1 resistor is connected at the input to Vcc and C1 capacitor is responsible for removing distortion and coupling audio signal to transistor BC 547 Base. R2 acts as a Collector coupling Resistor then output audio signal is received from Collector terminal and applied to Loud Speaker through C2 capacitor. By applying Bias above cutoff to transistor we can take no phase shift audio signal.

8 thoughts on “Simple Single Transistor Audio Amplifier Circuit

  1. 1.input and output voltages should have been indicated
    2.a variable resistor inthe input line is absent

  2. Will increasing the voltage from 9v to 12v increase the volume level, or would you have to recalculate the resistor values to compensate. I want to use a TIP120 Darlington transistor for an amplifier.

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