As we all know, Rout(closed) will decrease in Voltage-Voltage feedback.
The question is :?: if Av of amplifier(excluding feedback circuits) decreases too and why.
If you think Av equals to Av(closed) decreased by loop gain, I have the other question
:?:that why I can still use the Av(open) in the closed loop computing.
Dear all,
I have this problem for long:
As we all know, Rout(closed) will decrease in Voltage-Voltage feedback.
The question is :?: if Av of amplifier(excluding feedback circuits) decreases too and why.
If you think Av equal to Av(closed) decreased by loop gain, I have the other question
:?:that why I can still use the Av(open) in the closed loop computing.
Thanks.
I am not sure if I got your question, however I try an answer:
1.) The gain of the opamp without any feedback (Av) decreases with rising frequencies because each amplifier gain goes to zero for infinite frequencies (due to capacitive and delay effects)
2.) Therefore, all formulas which assume Av=infinite are valid only in a limited frequency range (in which this presumption holds approximately).