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RE: We should all read Bruno Putzeys' "The F-word"

Posted by 13th Duke of Wymbourne on June 7, 2022 at 14:07:01:
That is a good article but a bit esoteric. It is not applicable to our discussion here about the inherent linearity/non-linearity of active devices but it is about global feedback around a whole amplifier and how to add more. To keep stability, usually open-loop gain is rolled-off from a very low frequency so there is a lot of 'excess gain' at low frequencies to correct distortion but at higher frequencies less correction can be made. Mr Putzey presents a method to increase the gain at higher frequencies and still keep the closed loop system stable.
I believe the idea goes back to Bob Cordell for audio amplifiers but, I suspect, the concept itself is a lot older in the general field of system design and servo control.