Is your professor aware that an electret mic has the impedance-matching FET built-in ?

Hi Good day

I had a pause of the project because i was on exams.
I asked to a tutor about and the Microphone shouldnt have a Pre amplifier inside. So I will choose another model for the Electret Microphone (one without pre amplifier).
But what i have some doubts about the Impedance Matching, Theorically his function is to keep the same impedance from the input to the output. (to reduce signal loss).

I am kind of confused, it means that The Output from the mic that goes to the input to the FET (example 2.2k), the output from the FET should be 2,2k as well or i am wrong?
So the configuration of the circuit (resistor values) of the impedance matching should give me 2,2k impedance output.

And other thing that my tutor told me but i dont really understand. He told me to feed the microphone with a battery and not the same voltage source from the matching impedance. theorically why is that if someone knows?

and also recommend me to put a capacitor between the output of the microphone and the input of the impedance matching.

I am asking here because, i didnt understand the reasons of my tutor.

Thank in advance if someone knows the answer.

Cheers Larissa

 

So I will choose another model for the Electret Microphone (one without pre amplifier).

Difficult to source if you want to actually buy one. But ok if this is just a hypothetical setup.

 

hi lara,
Read this link.
http://en.wikipedia.org/wiki/Electret.

It explains the very high impedance of the electret material, this is why a very input high impedance amplifier is required, usually a FET, in order to provide a lower output impedance drive circuit.

The FET is used basically as a high to low impedance converter.

E

 

Hello,

The following video from EEVBLOG will give you information on the construction and use of the electret mic:
http://www.eevblog.com/2014/04/26/eevblog-608-condenser-electret-microphone-construction/

Bertus

 

Hello,

The following video from EEVBLOG will give you information on the construction and use of the electret mic:
http://www.eevblog.com/2014/04/26/eevblog-608-condenser-electret-microphone-construction/

Bertus

For me to make work the Microphone is not the problem, actually is the transistor.
in the microphone i am able to measure the sinusoidal signal with a oscilloscope at the output, but when i connected this output to the impedance wandler i am not able to get any signal in the output VDS. :/