jiaming_lee said:
examing small signal stablility is straightforward: just apply an AC simulation to check phase margin and gain margin.
However, AC sim assumes the unchaged DC OP (this is not true in real application), so it can not garentee the total 100% stablility. So, the large signal check is needed. Normally, connect the opamp into feedback mode as application does, then give DC and a very small sine wave to simulate the small signal; check the output. if no ringing, the opamp is stable in large signal. (monte carlo analysis would help to check the mismatch caused unstablility)
Hi jiaming_lee,
First of all, thanks for your reply!
Second, I have still two questions about large signal stability issue.
Q1: What do you mean by applying DC and a very small sine wave to simulate the small signal?
My guess
Do it mean doing transient analysis by applying addition of DC(large) and a very small sine wave(how small should it be)?)
Q2: Can any insights be given from the results of the above analysis? For example, any simple equations possible?
regards,
jordan76