PSRR peak at low frquency

[akashqwe]

Hi,
I have a single pole system.Ideally I expect one peak in the PSRR curve, at the Unity Gain Bandwidth freq. But I am getting two peaks, one at the low freq and the other at UGB. I can see similar behaviour in gian. can you someone explain this.
Thanks

 

[frankrose]

Hi, post a schematic at least, otherwise I think nobody will answer this. ínormally I wouln't expect any peak. And post some simulation results, plots too.

 

[dick_freebird]

Power supply rejection has two elements. One is the internal,
direct transfer function of d(OUT)/d(PS). The other is the
"outer loop" where AVOL fights the PS error "input" and tries
to null. The first is fast, direct; the second, slow and indirect
but the only one with any (helpful) gain. Slow loop PSRR works
well at DC and fades with increasing frequency, at roughly the
same slope as does AVOL (because AVOL is who's doing the
work).