About preampifier and amplifier designing

[sushmita agrawal]

How to design a preamplifier and an amplifier circuit for a very sensitive microphone signal having output is approximately 12mv .

 

[Dan Mills]

The usual amplifier topology for a low impedance microphone is a long tailed pair of large geometry transistors driving an opamp or similar.
Watch thermal noise in the resistors and if you are doing a input with P48 support, watch the various fault modes (short in the cable with the P48 turned on and the caps charged is usually worst case).

12mV is not actually all that low, a ribbon mic will be 20dB or more lower then that, and even most dynamics are lower then that unless close miced!

You should be designing for less then a few nV/root Hz over 20-20K, and do limit the bandwidth to 100K or so so as to avoid picking up the local radio station.

Or you could do the lazy thing and just stick a mic preamp chip from THAT Corp or TI or such on a board!

Board layout is in all cases important, both for circuit stability at high gain and for minimal excess noise and distortion.

Have fun, mic amps are nice simple analogue projects that still have some interesting bits.

REEegards, Dan.

 

[sushmita agrawal]

electronics circuit design

could any one tell me what will be the preamplifier and amplifier circuit disign and their components required for microphone having sensitivity of 30db ??

 

[Dan Mills]

Re: electronics circuit design

Sensitivity of 30db is meaningless, it needs a reference level.

A Gain of 30db would be a meaningful request, but it is short of a lot of information, noise performance requirements, does it need phantom, what LF corner frequency, distortion performance requirements, what power rails are available, is it power constrained, balanced or unbalanced input and output?

THAT corp have some nice single chip solutions that are really very good, as do TI and analog, pick a chip and follow the app note would be my approach unless I needed something unusual.

Regards, Dan.

 

[sushmita agrawal]

Digital signal processing

i m using a microphone of -30 dbv sensitivity which are giving an o/p signal of approximately 12 mv and we have to add a preamplifier and amplifier to enhance the o/p to 1.8 v which is required by our ADC in emote interfacing. actually if i use op-amp for desining amplifer then it wl genearte high noise..which is undesired so what kind of IC should i use for designing amplifier?

 

[BradtheRad]

Re: Digital signal processing

You can use a single transistor in common-emitter configuration.

 

[vikash23]

Hi,

Use the below development kit circuit diagram...

SSM2167 dev kit for noise cancellation from the mic

TPA0211 Dev kit for mic-pre amp.

Regards,
Vikash.