[sdiy] Bipolar Rail to Rail Opamp recommendation

Jacob Watters jacobwatters at gmail.com
Mon Mar 2 17:41:04 CET 2020


Someone shared this a while ago. It might help with the selection process.

Op Amp Shootout
https://docs.google.com/spreadsheets/d/1cfqitAdr0XEY4nd1PxWJ7wSBVZPki5V--rAdHqpQrGc/edit#gid=1880344491


*Jacob Watters*
JacobWatters.com <http://jacobwatters.com/>
Tel: 226-886-3526


On Mon, Mar 2, 2020 at 9:47 AM Schwarz Raphael <raphschwarz at gmail.com>
wrote:

>
>
> > Le 2 mars 2020 à 15:45, Schwarz Raphael <raphschwarz at gmail.com> a écrit
> :
> >
> >>> I read it so, that you're actually interested in clamping the input
> voltage. Why not bias the diodes to +5.8 and -5.8v instead?
> >>
> >> It is more like +-4.2 actually. :)
> >
> >
> > It’s actually a good idea
> >
> > I realized I overlooked the variation with forward current and
> temperature,
> >
> > I was a taking for granted the 0,8v drop , at 25° and 10mA it’s actually
> much less
> >
> > About 0.24v on a bat54s (what I was using)
> > About 0,65v on a 4148.
> >
> > Real life testing of a bunch of diode is consistent with this. My
> simulator has a very simplified model of diodes
> >
> > I wonder if biasing to about 4.75v is a practical solution with part
> tolerance , out of a bunch of bat54s I randomly tested it seems to only
> vary by a few mV
> >
> > temperature variation is not crazy for 10ma datasheet says 0,3v at 0°
> and 0.2v at 75°. So about 1% of 5V from 0° to 75°
> >
> > So it might be doable
> >
> > I still think a good rail to rail opamp would be a more elegant solution
> >
> > 1% of 5v is 50mV : something that could fit that range or slightly
> better would be enough. The application is keeping a bunch of gain to a
> maximum.
> >
> > Best,
> > Raphael
>
>
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