Cell phone micro phones

Thread Starter

DarthVolta

Joined Jan 27, 2015
182
I have a few broken cellphones, and I scraped 2-3 and never realized what the mircophones were. I just thought they were some inductor, (with a curious piece of plastic from the outside over it, I kind of thought it was RF related)

Until some little electrek mic's arrive I might try to get a mic from a phone working. Just for basic experiments with transistor's or say a LM386, what amount of AC current/voltage should I be appling to 1 of these? I'd say they are all pretty similar, and I think they are classic mic's, as in just a coil of wire around a magnet.
 
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Audioguru again

Joined Oct 21, 2019
674
I used the electret mic from my daughter's old cell phone in my FM transmitter 14 years ago then I transferred it into my Sound Level Indicator a few months later.

The Jfet in an electret mic (look at electret mic datasheets at Digikey) draws a max of 500uA (0.5mA) so I power it with a 10k resistor from a filtered 9V battery.

A "dynamic" mic has a coil of wire and a magnet like a tiny speaker. The earphone in a cell phone looks the same as a dynamic mic.

The crossover distortion and hissss from a lousy old LM358 dual opamp sounds horrible when used for audio.
 

Thread Starter

DarthVolta

Joined Jan 27, 2015
182
Yeah IDK I might have been describing the speaker. I have to scrap another one and get the mic.

Oh I meant LM386, I have some random salvaged audio chips too, I've barely played with audio circuits at all, since getting into EE. I should have bought mic's ages ago. I've been hitting the books a lot, so AC circuits should make a lot more sense. Same with basic radio cicuits, I can calulate a lot more of whats going on now, so I made a big rectangular loop antenna for making different types of AM receiver amplifier. I just wish I had a big old fashioned Vari-cap. I guess I could pull one of a working tube radio I have, yes I will.
 
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