Tuesday, 26 July 2016

Making a microphone pre amplifier using Opamp

Listing own voice on a speaker through a hand made microphone is fun stuff. I had some  electret microphones that I have salvaged from old phones.

why we need a mic preamp?
microphone is a transducer. It's output voltage is very low few millivolts only. But to drive a loudspeaker you need lot of power. so you need amplification. But If you put so less voltage to power transistor base nothing happens. Its requires a certain voltage or current to work with. Hence we need amplification of signal before feeding it to power amplifier stage. preamplifier exactly does that thing.

In my prototype I have uses a common Op Amp IC LM324 . It is not perfect for this but OK.
It works like a non inverting Amplifier with negative feedback.

Here Is the circuit Diagram jyotshna.com
Here is the image of my prototype