Best Way to Amplify Capacitive Microphone Output—Is LM386 Suitable?

Hello,

I want to amplify the output of a capacitive microphone, what's the best way for doing this?

Can LM386 be a good choice?

please help me, tnx.

By how much do you want to amplify the output? Also, wouldn't any audio amplifier work?

I need 100 gain voltage,
I have tested the suggested circuits in LM386 datasheet, but it didn't work!

Does the microphone you are using have an internal FET amplifier or is it a raw electret element?

If you search for "rode amplifier design" on youtube you can view a series of videos (EEVBlog) done by an experienced engineer on how to design very high performance microphone amplifiers.

My microphone doen't have any FET amplifier,
I have read that the maximum voltage that a microphone can produce, is 50mv. I want to increase this voltage to 5 volt.
What should I do?

There are lots of potential solutions and choosing the right one requires detailed knowledge about what you are trying to accomplish. You can optimize for low noise, high dynamic range, low distortion or low power usage.

Take a look at:
https://sites.google.com/a/vt.edu/amp_lab/pro...s/high-gain-low-noise-microphone-preamplifier

For a good high gain design and a detailed discussion of the design issues.

thanks, I have LM386 amplifier, but when I use its suggested circuit for 200 gain,
I don't achieve the expected result
What would the problem be?
Should I use a preamplifier? If yes, which preamplifier?!

I have done this many times. Ideally, you may need another component ahead of the LM386, depending on your microphone, but maybe not. Can you tell me more detail about what kind of microphone element you have? Does it have two wires or 3?

Hi Reyhane mohebali ,

pl ref my attachment it will help you.

Regards V.Sambath kumar.

It's a capacitor microphone and has two wires

Are you supplying the mic with a bias voltage? It needs and applied voltage in order for sound waves to make a signal. Without a bias it won't do anything.

That would work... Or you should be able to use your LM386, like this (see attachment)

I can't get the image, Would you please send it to my email?

I can't figure out how to do that on this forum, but it's a really simple circuit. Starting from left side...

9v Battery has + terminal at top and - terminal at bottom.
- terminal goes to ground.
+ terminal goes to + wire of microphone and to pin 6 of LM386
- terminal of microphone goes down to top of potentiometer(100kohm).
Bottom of potentiometer goes to ground.
Wiper of potentiometer goes to pin 3 of LM386
pin 2 of LM386 goes to ground
pin 4 of LM386 goes to ground
pin 7 of LM386 is not connected
between pin 1 and 8 of LM386 is a 10uF cap with +terminal on pin 1
pin 5 of LM386 goes to + terminal of 100uF coupling cap
- terminal of that 100uf cap goes to speaker/headphone.
other terminal of speaker goes to ground
also from pin 5 of LM386 is the plus side of 0.05uF cap
- side of that .05uF cap goes to top of 10 ohm resistor
bottom of 10ohm resistor goes to ground.

100kohm pot can be any value from 10kohm to 100k. If you don't have a pot, you can just put in a 100kohm resistor, but then you'll have no volume control.

Also, the .05uF cap and 10 ohm resistor are just there to eq out high frequency/hiss, so you can probably leave them out just for testing the circuit.

Hope this helps.
J