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I tried my biased electret but the ouput is very weak even when the gain of my oscop is at is highest?!
so there is not any insided gain circuit with the battery in these kinds of electeret mikes?
Normally, electret mikes do have an integrated FET amplifier.
And as MikeMl said you simply bias them with DC through impedance/current limiting resistor and Bingo ! It works ! And they provide relatively high output (> 100mV).
No.Normally, electret mikes do have an integrated FET amplifier.
Only if you scream loudly very close. The output is 5mV when talking in a normal conversation loudness about 10cm away.And they provide relatively high output (> 100mV).
There were some "condenser" mics that were bare but all electret mics have a Jfet. The Jfet is not used for gain.However if you have a bare unamplified electret cell, this is another game.
No. You are completely wrong since you are talking of a condenser mic. The high voltage is built-into the electret material of an electret mic and its Jfet takes care of matching the extremely high impedance of the diaphragm to the outside world.You will need three things:
1 - an amplifier with a VERY high input impedance (around 100M or 1 G ohm input impedance). Finding a MOSFET is an easy thing, finding a 100M or 1G ohm resistor is more difficult.
2 - A 60V (or so) low noise DC power supply with a 100M or 1G ohm output impedance. You can either use a lab supply with a 100M /1G ohm resistor or build a DC-DC converter to provide the requested voltage (witha ample outpur RC lowpass filtering) and
3 - A high quality (very low leakage) DC blocking capacitor. A small value (1nF) will do the job.
You bias your electret mike cell with your DC supply using the series resistor and
you use the capacitor at the electret cell output to prevent the DC voltage to reach the Hi-Z preamplifier.