enter image description here

I need to find the input/output impedances of this circuit (both open-loop and closed loop). I'm not sure how to deal with the Rf resistor as it lies in the middle.

I was thinking to use the Miller Theorem and do this, enter image description here

Would that be correcT?

  • \$\begingroup\$ Open loop, the Rin is 1/gm of M1. \$\endgroup\$ – analogsystemsrf Nov 25 '18 at 21:17
  • \$\begingroup\$ `@analogsystemsrf How come you ignored Rf? I know it's part of the feedback loop but when you break the feedback, Rf should go on one of the sides? \$\endgroup\$ – AlfroJang80 Nov 25 '18 at 21:36
  • \$\begingroup\$ If 1/gm << Rf, then we may chose to ignore it.. \$\endgroup\$ – analogsystemsrf Nov 25 '18 at 21:42

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