Hi everyone!

My first post on this site.

I have a problem with the amp circuit, i am in the process of creating. The purpose is to amplify a low mic signal in mV AC to volts. I have created a non-inverting amp with 2 stages. One with A = 100 and the next with A = 10.

So the problem is that there is only one third of the calculated gain in the first stage.

Resistor values are:
R1 = 90.9 Ω and
R2 = a series of 7k5 Ωand 1k47 Ω = 8970 Ω

this should give an amplification of ≈ 99.6

In my test setup i send in 3 mV of AC sine wave 1 kHz, but i only measure around 99 mV on the output of the opamp, wich is an amplification of ≈ 33. I am using a TLE2074 opamp, with +/- 6v on the supply.

Can anyone say anything about what might cause this problem?

best regards
Andreas

 

If you want us to look for why your circuit isn't working as you intended, don't you think it might be just a tad helpful if you posted what your circuit looks like?

 

It would be nice to see the schematic.

It would also be nice to see clear picture of the finished product, top and bottom if on a PCB, to look and ensure you wired it per your schematic.