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Distortion reduction by feedback (Read 2463 times)

ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Distortion reduction by feedback Oct 20^th, 2006, 1:59am Hi Guys, If the second hamonic distortion is d2 for an open loop amplifier, what is it when the amplifier is put into a feedback loop? The open loop gain of the amplifier is A, the feedback factor is F. Best regards, Yawei
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vivkr

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Re: Distortion reduction by feedback
Reply #1 - Oct 20^th, 2006, 5:22am

Hi Yawei,

It is not clear if the d2 in your expression refers to the distortion level or the
second-order coefficient in the input-output relation:

e.g. y(x) = a0 + a1. x + a2.x^2 + ...

Nonetheless, the important point is that you can improve the relation of the second harmonic to the
fundamental by a factor of (1 + AH)^2 when going from open-loop to closed-loop. Please see Razavi's book on
analog IC design (Chapter 13 on Nonlinearity and Mismatch).

Regards
Vivek

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ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Re: Distortion reduction by feedback Reply #2 - Oct 24^th, 2006, 9:29pm Hi Vivek, I want to know the relation of the second harmonic to the fundamental. It is clear in Razavi's book an analog IC design. Thanks Yawei
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