[sdiy] Bipolar Rail to Rail Opamp recommendation

[Pete Hartman]

That spreadsheet is very useful.

According to the datasheet, TLC227X op amps can do rail to rail, and I've
seen them used in some synth projects.  I have no idea how their other
specs stack up for what you need though, I'd cross check against the data
sheet.  I don't see them on the spreadsheet.

Pete


On Mon, Mar 2, 2020 at 10:43 AM Jacob Watters <jacobwatters at gmail.com>
wrote:

> 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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