Note that the region between the 1/k line and the Aol response gives you the loop gain in dB - and at w=wo we have unity loop gain. ![]() What I cannot understand is why can we find/use the close-loop gain on the bode plot of "Open-loop gain vs frequency" ?Įxample: Non-inverting amplifier with closed-loop gain:Īcl=Aol/(1+kAol)=1/ (with open-loop gain Aol and feedback factor k.)įor low frequencies (Aol>k and 1/Aol>wo the horizontal line (1/k) is above the Aol curve - now we have 1/k>Aol or k<<Aol.Īs a consequence, the feedback factor k can be neglected in the Acl expression and the closed-loop gain now can be approximated by Acl=Aol.īoth regions are separated by the frequency wo where we have Aol=1/k (loop gain k*Aol=1).Hence, wo is the frequency that determines the bandwidth for the closed-loop gain Acl.
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