AW: Re: AW[n]: Re[2]: LF411 Op-Amp dilem

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Fri Jan 24 21:05:00 CET 1997



> >What exactly do you mean by "feedforward"? I only know about
> >the common technique of using the miller effect on a cap
> >between the b and c of a transistor in some gain stage of
> >an opamp. Do you mean *this* being crap audio, or are you
> >speaking of something else? And how's the compensation
> >done in the "better" opamps?
>
> "Feedfoward compensation" is a means of "artificially" increasing the
> slew rate of a stage via differentiation. It's basically positive
> feedback, and it creates instabilities which MUST be compensated for
> via negative feedback. Once upon a time this was pretty widespread in
> vacuum tube circuits, but it's rarely even used there anymore.

Hmm, I just took a brief look into the data books (very brief, so I may
be wrong). Looks like the LF35x have the gain stage slowed down
by a small cap, making advantage of the miller effect. Just like
1000 other opamps. Sure, it is not the best of all possible methods,
but again: in what does it differ from a TL071, or any other comparable
opamp?

JH.



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