Thanks, yes I believe there is a real threat of instability here. Please could you check if the following would be unstable? (schematic attached) I have used “out of loop compensation”, as given on page 20 of the following article, kindly provided by asdf44….
Opamp stability document:
https://www.analog.com/media/en/ana...umber-2/articles/volume31-number2.pdf#page=19
....This just puts a compensation resistor in between opamp output and load capacitor (as many above kindly described).
The opamp output pole from the 200nF capacitor alone (no 4r7) would be 1/(2*pi*RL*CL)
Where RL = 976ohms (load on opamp output)
This pole is at 815Hz.
Adding the 4R7 compensation resistor adds a zero. According to page 20, this zero is at 6950 Hz.
This zero must be at least a decade in frequency below the closed loop bandwidth of the opamp circuit without the 4R7 compensation resistor. (ie just the 200nF load capacitor). –To find this bandwidth, the MIC6211 datasheet is used….and the pole at 815Hz is where the gain of 82dB can be said to fall off at 40dB/decade.
This line joins the 0dB axis at 815Hz/ [10^(-82/40)] = 91440 Hz
…this is at least a decade above 815Hz, therefore the 4R7 compensation resistor added in the attached will stabilise this opamp.
Would you agree?
Clearly there is something wrong here because it calculates that even a 1 milliOhm compensation resistor would give stability.
i think the zero frequency calculation of page 20 is wrong. (i also noticed that the schem on the RHS of page 20 is wrong, it has feedback going into the non-inverting input)
MIC6211 opamp datasheet
https://ww1.microchip.com/downloads/en/DeviceDoc/mic6211.pdf