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I think both is unstable. If u have point where gain is 0 dB and phase shift >= 180 deg than in closed loop configuration that circuit will be not stable.
I can tell you some rule :
1.IN many cmos circuit design book tell us ,at the UGBW,the phase margin will at least 45deg,but in our practice circuit ,the phase margin usually 60deg ,in some A/D circuit ,the Phase margin will 70~80 deg ;
2.AS a amp circuit ,you have to see the closed AC characteristics ,this will give you the meaning.
3. gain margin :when the AC Frequence to 0deg or -180(the same ),the gain must below a certain value,usually -10db(this can vary as you circuit design requirement),and ensure the gain curve
drop
4.The transition of the ac frequence will 3 multiple of the UGBW ,this ensure the stable
Added after 2 minutes:
so the two amp are unsuccessful design ,they will appear stable problem
Added after 13 seconds:
so the two amp are unsuccessful design ,they will appear stable problem
Added after 10 seconds:
so the two amp are unsuccessful design ,they will appear stable problem
Added after 1 seconds:
so the two amp are unsuccessful design ,they will appear stable problem
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