Electret Condenser Microphone Amplifier

The circuit takes the audio signal rom the condenser microphone and amplifier it, so you can use the microphone as the input to some device which wouldn't normally accept microphone level signals (which are very low).

The amplifier has an adjustable gain, which is performed via. R1 (a 1 Mega Ohm variable resistor). It controls the feedback of the 741 opamp, which in turn drive a 2N2222 output transistor.

• U1 - LM741 op amp ic
• R1 - 1 megohm resistor
• R2, R3 - 6.8k ohm resistor
• R4 - 1k ohm resistor
• C1, C2 - 0.47uF ceramic capacitor
• MIC1 - electret condenser microphone

All resistors are 5 or 10 percent tolerance, 1/4-watt. All capacitors are 10 percent tolerance, rated 35 volts or higher.