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An Instrumentation Amplifier as a preamplifier for electret mic

Question asked by Dave1989 on Aug 2, 2013
Latest reply on Aug 6, 2013 by KJBob

Hello everyone,

I'm a 4th year undergraduate student in EE and I have a question for my graduation project.

My project is to measure elephant calls in the Infrasonic frequency (<20Hz) range AND also in the audible range ( till about 5KHz) and to do DSP on it with MATLAB.

The the block diagram/Signal chain looks something like this:

Elephant calls -> Electret microphone -> Preamplifier -> DAQ ( NI 6008 USB ) -> Laptop (MATLAB).


My advisor suggested that I use an Instrumentation amplifier for the amplification of the signal.

The reason for this choice is the fact that the amplifier is differential and has a high CMR.

I'm using the Panasonic wm-62 electret mic capsule for this project, which has a frequency response well below 20Hz.


I've already bought the AD620 amp with DIP connections.


My question/problem that I'm now facing is how to connect the electret mic to the amp. I don't know how to design a preamplifier that will cover the wanted frequency spectrum ( 1Hz - 5000Hz ). For example I don't know how to bias the amp, which values for caps and resistors to choose, which coupling capacitors to use etc.

I'm very confused at this point.


Can someone please show me a schematics for a circuit that will answer my needs? My advisor is no help at this point as he's a DSP guy and not analog design guy.


Any help will be highly appreciated.