[roadbuster]

Hello,

Does anyone have a quantitative measure of the noise at the output of a "cmoy" amplifier using an OPA2132PA (or similar) op-amp? I just threw the basic circuit together using good quality components and I'm getting, in my opinion, a significant amount of noise on the output line (on the order of 100mV) when there's zero input signal.

Considering the amplifier is nothing more than a non-inverting, positive-gain amplifier with a low-pass filter at the input, I wasn't expecting particularly good performance. The noise can be mitigated using 0.1uF bypass capacitors between the supply and virtual ground rails, but it's still high enough to make me wonder whether this is common or just an issue that I'm facing.

Anyone have any experiences to share?

 

[Megaptera]

100mV on the output is wicked high. Most of the ones I've built are on the order of 1-5mV. There's been plenty of talk on how to diagnose and reduce that if you search for 'dc offset' -- I'd put money on the opamp oscillating, myself.

 

[roadbuster]

The op-amp is oscillating, there's no doubt about that, but the oscillation frequencies are 100KHz and 10MHz right now. I'm considering adding an additional series resistance in series with the bypass capacitor on the supply rails to the op-amp, but I'm almost certain that IR drop will be an issue if I do that.

Perhaps I shouldn't be so lazy and build the circuit on a proto or vector board rather than a silly breadboard

Thanks for the response. It's always appreciated.