**Part Number:**OPA2325

**Other Parts Discussed in Thread:**OPA2837, TEST

Hello,

I'm looking to do a fairly simple transimpedance stage running at 10-20kHz, and I'd like to eliminate the error due to finite open loop gain, as far as possible. Datasheet shows typical OL gain of about 60dB at 10kHz so the transimpedance stage on its own will have an error of about 0.1% due to this. One thought I had was that I could follow the transimpedance stage (with its negative gain) with a simple buffer with x1 gain, which would also be handy for driving directly into an ADC input.

If I do this, I get that the transfer function (ignoring bias currents) to be:

If the open loop gains of the two amps are perfectly matched then the middle two terms in the denominator cancel and the effect of finite Aol becomes quite small. What I'm unsure about is just how well matched the gains of the two amps will be in reality. Since they're physically on the same chip I'd assume any difference will be small, but how small? At any given frequency, would there realistically be more than 1dB difference?

Thanks,

Gordon.