[sdiy] Bipolar Rail to Rail Opamp recommendation

[Brian Willoughby]

op amps do not have a ground pin, just +V and -V. So your requirements specify a 10 V op amp.

I was just about to share my experience that rail-to-rail op amps seem to be limited to 5 V supply ranges, but then I did a quick search of Mouser, plugging your requirements into the minimum and maximum supply constraints. Looks like there are plenty of RROI (rail-to-rail input/output) op amps listed, so my experience was not complete. Top of the list are Texas Instruments TLV and OPA chips.


Assuming that you’re in a Eurorack scenario, why not just use a 24 V supply for the op amp, and use other signal conditioning techniques to guarantee that the inputs and/or outputs are clamped to ±5 V ? You’ll have much more control, and you can buy op amps that aren’t rail-to-rail because you won’t be anywhere close.

I also wanted to point out that op amps can draw an unexpected amount of current when you purposely exceed their voltage limits. If your goal is to clamp the mix of CV inputs, then you should design circuit elements specifically for that feature, rather than pop in a rail-to-rail op amp fed by ±5 V and expect it to handle the task gracefully.

Brian


On Mar 1, 2020, at 7:10 AM, Schwarz Raphael <raphschwarz at gmail.com> wrote:
> 
> What would you recommend as good not too expensive bipolar rail to rail op amp
> 
> I have several cv inputs mixed and I need to keep the sum between -5/+5v. 
> It needs to go as close as possible to the supply rails (-5/+5v) and have reasonable offset .
> 
> I initially used diodes but 0.8v is too much.
> 
> I’m kind of lost there are so many references .
> 
> Best,
> Raphael