# How Does a Microphone Work? - Comments Welcome - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

balajisu
Post subject: How does a microphone work? - Comments welcome Posted: Wed Aug 30, 2006 5:33 pm

Captain

Joined: Wed Jul 06, 2005 5:54 pm
Posts: 24
Location: Germantown,MD
I'm new at designing microphone circuitry. Need some valuable tips in this regard. Microphones need supply voltage of 8V or 12 V. Would these microphones be functional if I only supply them 5 V or a lower voltage than what is required by making sure that they draw same amount of current(using a different biasing circuit)

Any comments on this would be much appreciated.

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nubbage
Post subject: How Does a Microphone Work?Posted: Thu Aug 31, 2006 7:05 am

General

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
An electret microphone needs only about 1.5 volts to bias it.

The way to test it is apply bias of 1.5V and ac couple the output to an audio amp or oscilloscope through a capacitor of about 1 microF.

I am not sure though what the consequences would be if you bias it with the wrong polarity ie swap positive and negative.

You often see circuits where they are fed from say 9 or 12 volts, but that is because the voltage is available for other purposes. In effect, the circuit designer drives the element through a constant current source: a high value resistor. But the voltage across the element needs to be only 1.5 volts or so.

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balajisu
Post subject: Posted: Thu Aug 31, 2006 9:58 am

Captain

Joined: Wed Jul 06, 2005 5:54 pm
Posts: 24
Location: Germantown,MD
Thanks for the info

Posted  11/12/2012

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