What does "Fet" exactly mean in regards to the mic

[The Gibbon]

I guess I'm a bit unclear on what "FET" means....a little help?

[joel hamilton]

It means a "Field Effect Transistor" is used to amplify the miniscule signal output of the diaphragm instead of a tube.

[The Gibbon]

Thanks Joel...but now I have another question for you...does that mean that a condenser mic that has no tube can be called a Fet?...thanks for your help...I'm just trying to settle a little squabble with a buddy on this issue.

[lobstman]

I guess I'm a bit unclear on what "FET" means....a little help?

A FET is a semiconductor with a very high input impedance. Since a condenser mic diaphragm produces such a small voltage, you don't want to load it down going into the next stage with a low input impedance (Ohm's law for impedance I=E/Z). For all practical purposes, this means you need a tube or a FET as a buffer stage (there are a couple rare exceptions, but that's way over my head). FET mics were developed in the '60s as a replacement for tubes- they were more reliable, quieter, and required less power. Of course, FETs don't sound the same as the tubes did. There are also many different kinds of FETs, just as there are different kinds of tubes.

Anyway, virtually any condenser mic that doesn't use a tube has a FET in it.