Microphone preamplifier

Thread Starter


Joined May 14, 2010
Hi guys!
I want to design an audio amplifier. I have deigned the power amplifier with 20 W output to 4 ohm speaker. Now I should design a two stage microphone preamplifier with 20 V output and 50 mV (Overall gain=400) input operating between 20Hz and 20KHz. The DC power supply should have 30 V (VCC) because the same DC source should be used for both power and preamplifier circuits.
Can anybody help me?
Thank u!


Joined Dec 20, 2007
A power amplifier usually has a voltage gain of 30 to 100 so it can ber driven from a line output of 220mV from an MP3 player or some other music player.
You don't say which type of microphone (dynamic or electret) but their outputs are about the same at 5mV to 20mV, not 50mV.