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Groups > sci.electronics.design > #454677
| From | Winfield Hill <hill@rowland.harvard.edu> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: Another op-amp stability question (LT1677) |
| Date | 2017-04-01 16:46 -0700 |
| Organization | Rowland Institute |
| Message-ID | <obpe3o0174h@drn.newsguy.com> (permalink) |
| References | <28246daf-fd57-48e6-a94e-2e778c9a3973@googlegroups.com> <049f13d9-358b-4173-aa2c-13af79004b7f@googlegroups.com> |
John Miles, KE5FX wrote...
>
>On Saturday, April 1, 2017 at 9:16:52 AM UTC-7, tabb...@gmail.com wrote:
>> It's a known issue with some opamps, but I've stayed quiet cos I can't
>> remember where a datasheet (IIRC) talks about it. IIRC the advise was
>> to keep source impedance under 10k, and the cause is stray capacitive
>> coupling from output to input plus a faster input stage than output
>> stage. But as I say, I can't remember where this was from so ICBW.
>
>Doesn't seem like a typical phase-margin gotcha, or one that involves external
>coupling or feedback of any kind. There's no sensitivity to stray C at
>all. There must be a thermal component to the phenomenon, because it's only
>noticeable at very low frequencies and is quite sensitive to temperature. The
>oscillation itself is around 700 - 800 kHz but I've never seen it appear on
>signals above a few kHz. No electrical time constants are anywhere near that.
>
>Given that people don't usually use pricy low-noise opamps with high-
>resistance sources, I guess it's not too surprising that the issue isn't
>well-known. That's no excuse for manufacturers not knowing about it and
>warning accordingly, though.
Yes, John. But I think its safe to say opamps going through
input-pair transitions at certain voltages are suspect to be
used at those voltages. Your experience illustrates that point.
--
Thanks,
- Win
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Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 00:37 -0700
Another op-amp stability question (LT1677) pcdhobbs@gmail.com - 2017-03-29 04:50 -0700
Re: Another op-amp stability question (LT1677) piglet <erichpwagner@hotmail.com> - 2017-03-29 13:23 +0100
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 10:58 -0700
Re: Another op-amp stability question (LT1677) tabbypurr@gmail.com - 2017-03-29 11:15 -0700
Re: Another op-amp stability question (LT1677) Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-03-29 23:29 +0200
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 17:14 -0700
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 18:06 -0700
Re: Another op-amp stability question (LT1677) Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-03-31 14:40 +0200
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-31 14:49 -0700
Re: Another op-amp stability question (LT1677) Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-31 20:39 -0400
Re: Another op-amp stability question (LT1677) tabbypurr@gmail.com - 2017-04-01 09:16 -0700
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-04-01 15:03 -0700
Re: Another op-amp stability question (LT1677) Winfield Hill <hill@rowland.harvard.edu> - 2017-04-01 16:46 -0700
Re: Another op-amp stability question (LT1677) John Larkin <jjlarkin@highlandtechnology.com> - 2017-04-01 17:31 -0700
Re: Another op-amp stability question (LT1677) tabbypurr@gmail.com - 2017-04-01 20:59 -0700
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-04-01 21:41 -0700
Re: Another op-amp stability question (LT1677) tabbypurr@gmail.com - 2017-04-02 04:53 -0700
Re: Another op-amp stability question (LT1677) John S <Sophi.2@invalid.org> - 2017-04-02 16:26 -0500
Re: Another op-amp stability question (LT1677) krw@notreal.com - 2017-04-02 19:29 -0400
Re: Another op-amp stability question (LT1677) John S <Sophi.2@invalid.org> - 2017-04-02 18:34 -0500
Re: Another op-amp stability question (LT1677) John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-29 05:18 -0700
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 10:56 -0700
Re: Another op-amp stability question (LT1677) John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-29 13:02 -0700
Re: Another op-amp stability question (LT1677) "John Miles, KE5FX" <jmiles@gmail.com> - 2017-03-29 17:57 -0700
Re: Another op-amp stability question (LT1677) John S <Sophi.2@invalid.org> - 2017-04-02 16:31 -0500
Re: Another op-amp stability question (LT1677) John Larkin <jjlarkin@highlandtechnology.com> - 2017-04-15 08:58 -0700
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