Hello!

I am designing a microphone array beamformer for a science fair project for which i need eight identical amplifiers. I cannot get the LM324 quad op-amp to work properly. I first built an inverting op-amp design with 1k input resistance and 100k feedback resistance, but only got unity gain. I built a non-inverting op-amp with 1k resistance between the inverting input and ground, and a 10k feedback resistor from output to the inverting input (circuit diagram attached; ignore resistance values in diagram). The circuit worked splendidly for a moment, then stopped producing output totally as if it had burned out. Yet when I switched in a different 324 there was no change. I have similar problems with most Op-Amps. Any ideas on how to fix this or pointers on Op-Amp use in general? I am using a capacitor-coupled electret mic for input.

Thanks!

 

Hello,

You showed us only a part of the schematic.
What are you using as powersupply?
Is it a single or dual powersupply?
What are the voltages from the powersupply?

Bertus

 

We need your complete schematic to be able to really help.

The LM324 is an old part, it can't do audio very well at all. A TL084 is much better, but has its own set of limitations.

 

AudioGuru posted this electret mic preamp awhile back:

If the sound quality isn't important, and you have at least 9v available for Vcc, you could use a TL082 dual opamp. They're available at your local Radio Shack.