Re: pahse shift in ldo
I think the schematic you are referring is:
One Error Amplifier => PMOS.
And the feedback path is connected back to non-inverting input of error amplifier. But you couldnt look at it and conclude it is positive feedback.
If you look at whole system (Error Amp + PMOS), it is equivalent to Negative Feedback since there is one inversion through the PMOS (Input=Gate of PMOS=Output of Error Amp, and Output of LDO = Drain of PMOS). IF you look at PMOS, it is in Common Source structure which has one more gain stage to drive the output.
Hope it helps.