Not sure what the capacitor does in this opamp stage..

Hi there,

I have been looking at a power supply on the web and struck the use of a capacitor in series with a resistor in a current limit inverting opamp stage.

Here is the circuit:

View attachment 61927

what does the capacitor do in this regard?

Does it still work as an inverting stage or does the capacitor change what it does fundamentally?

Kind regards

Simon

I haven't spend a lot of time to analyze it, but it looks to be a sort of delay to protect against suddenly turnoff in case of short current spikes in load.

It rolls off the high frequency response of the op amps (low-pass filter function) with a corner frequency determined by the RC time constants (R19-C8 and R11-C4). It may be to avoid high frequency instability.

Hi,

Yes, it's part of the feedback system compensation, or at least it looks like it is.
The resistor and capacitor make up the network, but usually there's another capacitor too for type II compensation.
Compensation in a feedback system is necessary when the system would oscillate or have serious overshoot or long settling time or any combination of these. The system is either unstable or marginally stable but with the right little network in the feedback path of the amplifier the system becomes more stable.
There's various techniques for selecting the compensation network component values, but they are all a little involved. Im sure there is plenty on the web about this though. It helps to do a Root Locus too.