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Re: OpAmp Feedback Resistance vs. Stability

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From	Hul Tytus <ht@panix.com>
Newsgroups	sci.electronics.design
Subject	Re: OpAmp Feedback Resistance vs. Stability
Date	Thu, 30 Mar 2017 06:09:17 +0000 (UTC)
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Familiar numbers. Nice to see the correct ones.

Hul

tabbypurr@gmail.com wrote:
> On Thursday, 30 March 2017 04:18:18 UTC+1, Tim Wescott  wrote:
> > On Wed, 29 Mar 2017 22:54:13 +0000, Hul Tytus wrote:
> > 
> > > Tim - the early opamps (lm707??) required "compensation" so that the
> > > loop gain was less than unity at the frequency where the phase shift was
> > > 180 degrees. The first opamp that completely compensated itself, ie
> > > could be used at unity gain with no weird behavior, was, I think, the
> > > single version of the lm747.
> > >    Those versions that required compensation had special pins for
> > > capacitors. But the circuitry between the output and the negative input
> > > could also be used for compensation, that is to reduce the loop gain
> > > with a low frequency rc filter. That is probably what you were doing
> > > with the rail to rail opamp. A 1K resister and 20 pf creates a 3 db
> > > point around 8 mhz or so.
> > 
> > I got out of college just as those weren't being used much any more.

> The 709 was the popular uncompensated one, and the 741 the number 1 unity stable opamp for a long time. There were others of course before & after, eg the 702. And even valve opamps.


> NT

Thread

OpAmp Feedback Resistance vs. Stability Tim Wescott <seemywebsite@myfooter.really> - 2017-03-28 17:12 -0500
  Re: OpAmp Feedback Resistance vs. Stability Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-28 15:17 -0700
    Re: OpAmp Feedback Resistance vs. Stability Tim Wescott <seemywebsite@myfooter.really> - 2017-03-28 17:21 -0500
    Re: OpAmp Feedback Resistance vs. Stability Tim Wescott <tim@seemywebsite.com> - 2017-03-29 11:57 -0500
      Re: OpAmp Feedback Resistance vs. Stability Hul Tytus <ht@panix.com> - 2017-03-29 22:54 +0000
        Re: OpAmp Feedback Resistance vs. Stability Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-29 16:31 -0700
          Re: OpAmp Feedback Resistance vs. Stability George Herold <gherold@teachspin.com> - 2017-03-29 18:29 -0700
            Re: OpAmp Feedback Resistance vs. Stability George Herold <gherold@teachspin.com> - 2017-03-29 18:46 -0700
          Re: OpAmp Feedback Resistance vs. Stability Hul Tytus <ht@panix.com> - 2017-03-30 06:02 +0000
        Re: OpAmp Feedback Resistance vs. Stability Tim Wescott <tim@seemywebsite.com> - 2017-03-29 22:18 -0500
          Re: OpAmp Feedback Resistance vs. Stability tabbypurr@gmail.com - 2017-03-29 21:24 -0700
            Re: OpAmp Feedback Resistance vs. Stability Hul Tytus <ht@panix.com> - 2017-03-30 06:09 +0000
  Re: OpAmp Feedback Resistance vs. Stability Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-28 18:27 -0400
    Re: OpAmp Feedback Resistance vs. Stability bitrex <bitrex@de.lete.earthlink.net> - 2017-03-28 18:47 -0400
  Re: OpAmp Feedback Resistance vs. Stability John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-28 15:37 -0700
  Re: OpAmp Feedback Resistance vs. Stability George Herold <gherold@teachspin.com> - 2017-03-29 05:41 -0700

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