the regulator's AC simulation can't match the transition simulation.

[sj95]

Dear all:

I have a liner voltage regulator, I let its phase beyond 180 degree, I guess it should be unstable in transition simulation since it has no phase margin.

But it's not, it is still stable in transiton simulation.

Why the AC simulation can't match the transition simulation ?

Anybody has the problem before ?

thanks~

 

[dgnani]

assuming what you said is really true, remember that many stability conditions are only sufficient not necessary for stability...

posting your simulation schematic and Bode plot might help us help you

 

[LvW]

I have a liner voltage regulator, I let its phase beyond 180 degree,.........

What does this mean (--I let its phase beyond....)?
Which phase? If you need help, we need a clear description of the problem.

 

[dick_freebird]

Because transient responses worth looking at, are not small
signal. Thus the AC analysis result has not much to say about
anything but the final settling response. A well designed
linear regulator may in fact respond very differently at
large error than small signal, on purpose.