How to make sure the stability of a OP-based integrator?
Do I need to break the feedback loop to measure the loop gain and phase margin?
Or, just use a step response to check the stability?
Yes, you need to break the feedback loop to measure the loop gain and phase margin, and don't forget to add the parasitical input capacitor of the amplifier.
The simple method is putting a step pulse signal on the input terminal, do a transient simulating and check output overshoot before reaching steady state.If overshoot is very large ,the integrator isn't stability!