We sometimes need a Simple microphone, But we cannot find it. This circuit can be help us modify the normal small speaker to microphone as pre-mic circuit.
This is the generally Microphone Preamplifier circuit When entering the power supply circuit for Q1 will work as an amplifier in common base.
That matching the input impedance of the Impact of Impact Speaker impedance low.
When signal sound into the speakers.Audio is converted to electrical signals through C2.
In addition, C2 to prevent voltage direct current flows into the speaker.
The signal goes through C2 drop across R3 is a voltage signal sound.
When Q1-BC109 work, will result in pressure changes pin B of Q2.This is the amplifier changes, the current implementation of Q2 change.
If the speaker signal to drop across R3 is positive.The Q2 will be very current.If the incoming signal is negative, Q2 will be less current.
The output is a voltage drop across R4. The C3 protects the DC, not to flow into the.