Help me with microphone interface design

[johnchau123]

One of my friends are designing the microphone interface, but he is stuck at some problems. I hope you all can help him.

The problem is

(1) the microphone can only detect signal only with zero or very very short distance
(2) can't amplify the signal under my control with the use of non-inverting amplifier. (LM741)

I know insufficient data is given, but I hope you all can help him.

Thanks.

 

[rogerynt]

Re: Microphone interface

1.) Check mic bias.

assume 3V Vdd, mic connection

e.g. For differential input : Vdd - 1K res. - mic - 1K res. - gnd
For single end : Vdd - 2K2 res - mic - gnd

( make sure ac couple to the op-amp. )

2.) Gain level - with proper bias the mic normally induce a 5 ~ 8 mV signal so sufficient gain is needed for the amp.

( assume use small condensor mic with ~ 44dB sensitivity )

Roger

 

[dindeds]

Re: Microphone interface

You can interface this circuit to almost any audio inputs and hv sufficient gain.

 

[eanic]

Re: Microphone interface

here is circuit Pre MIC, easy to build.
https://www.elecfree.com/electronic/category/microphone-preamplifier/