Original question:
We have this second stage summing amplifier with OPA855, which is not stable for gains < 7V/V.
The first stage is a gain 7 OPA855 amplifier that works fine. Is there a way to stabilize it for gains between 1 and 3 using noise shaping techniques with the input and feedback capacitors?
Morning Daniel,
There is of course a way to do that, but -
If all your source (L1C2 to L8C2) are on and showing low impedance looking back, is not your Noise Gain 1+ (453/(453/8)) or a noise gain of 9V/V. Should be ok , it would seem.
However, there is a technique I wrote up many years ago and use all the time to shape noise gain (tuning phase margin) for decomp op amps using a feedback cap and cap to ground on the inverting input pin - if you need it.
If you need it, the original article was rebuilt some years back and appears here -
I used it here in this more recent article as well -
And then in each of the decomp amp datasheets I have done, I try to included a simplified discussion of using this - look at the OPA838 datasheet.
