Help me solve a strange phase shift increase

[surreyian]

Hello,

Normally, there is a phase shift of -45deg at -3dB gain, however, in my circuit there is a +45 deg phase shift. I think it is due to the compensation cap in feedforward mode.
This give no phase margin.
Anyone knows how to compensation in this condition for phase margin?

 

[dick_freebird]

Re: phase shift increase

If your comp cap is feeding more power forward than the
amplifier (?) then that's not a very good amplifier (or maybe
you are driving with an unrealistically stiff source). Usually
when I see a phase shift that doesn't make sense, it's due
to the amplifier being at a bad operating point and not working
as intended. Especially if you are going by small signal results
which are set up by operating point and can't overcome it
the way a transient simulation might.