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Re: nice little opamp

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On Sun, 16 Oct 2016 09:49:26 -0700, John Larkin wrote:

> On Sun, 16 Oct 2016 04:36:08 -0000 (UTC), Frank Miles
> <fpm@u.washington.edu> wrote:
> 
>>On Sat, 15 Oct 2016 12:19:02 -0700, John Larkin wrote:
>>
>>> http://www.onsemi.com/PowerSolutions/product.do?id=NCS2005
>>> 
>>> This is rrio, 8 MHz, 32 volts max supply.
>>> 
>>> It seems to be c-load stable at 1 uF and up, ceramic or tantalum,
>>> which means it can drive bypassed reference rails and low-current
>>> power rails.
>>> 
>>> It rails clean, so will work as a comparator, but above 20 volt supply
>>> the positive clamp gets a little strange.
>>> 
>>> 40 cents each by the reel.
>>
>>Maybe my PDF reader is altering things, but I see only stability at 1nF
>>load (in both data sheet and cover - feature list).  Transient responses
>>are shown with only ~25pF load.  The voltage drift is rendering in uV/C,
>>so the "micro" character seems ok.  {This is with both xpdf and evince
>>on a linux system).
>>
>>Perhaps you have some information from a source other than your link?
>>
>>
> I experimented with one. It gets a little fuzzy with 10 nF loads, but
> stabilizes nicely with microfarads.

Ah, from testing.  Seems similar to some of the TLx431 family loading 
zones.

Hopefully OnSemi won't change their process on you mid-production, 
continuing to meet their specs but not your expectations.

> Opamps are fairly unpredictable as regards their c-load behavior. RRO
> parts are often capacitance tolerant, but it depends on how they do the
> internal rolloff. Data sheets used to have internal schematics, which is
> getting rare these days.

Sad.  But as long as we buy the devices, the manufacturers will continue
to do this (and probably continue making data sheets less comprehensive).

> My ideal opamp is single SOT23, rrio, low noise, low offset, low bias
> current, fairly fast, c-load tolerant, 3 to 30 volt supply, and cheap.

And low power consumption, and guaranteed availability for ____ time.  
Please let us all know when you find this part!

> OPA197 is a candidate, but I haven't tested it yet. It's 67 cents in
> reel quantity. The EMI filtering is nice. It works down to 4.5 volts and
> can output +-40 mA, so it might be worth another 30 cents.

At least this data sheet shows more information regarding C-load behavior.

   Thanks,
   Frank

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nice little opamp John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-15 12:19 -0700
  nice little opamp Phil Hobbs <pcdhobbs@gmail.com> - 2016-10-15 13:24 -0700
    Re: nice little opamp John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-15 14:03 -0700
    Re: nice little opamp Winfield Hill <hill@rowland.harvard.edu> - 2016-10-15 14:32 -0700
      Re: nice little opamp Phil Hobbs <pcdhobbs@gmail.com> - 2016-10-15 14:45 -0700
      Re: nice little opamp John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-15 15:24 -0700
      Re: nice little opamp krw <krw@nowhere.com> - 2016-10-15 20:08 -0400
  Re: nice little opamp Frank Miles <fpm@u.washington.edu> - 2016-10-16 04:36 +0000
    Re: nice little opamp John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-16 09:49 -0700
      Re: nice little opamp Frank Miles <fpm@u.washington.edu> - 2016-10-16 23:42 +0000

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