[sdiy] low input bias current opamps

[rsdio at audiobanshee.com]

Aren’t *all* S/H circuits discrete in the sense that the capacitor is always external? I mean, you still have to be concerned with guard rings and other layout issues that can affect the performance.

Personally, when I need a lot of S/H channels, I prefer to have a large analog multiplexer and quad op amps to keep the PCB size reasonable. We’re talking about 32-channel systems where there just isn’t room for 32 individual 8-pin packages. It’s possible to find quad op-amps with *FET inputs with extremely high impedance and ultra low leakage. Unfortunately, they are usually limited in other ways. At least the LFx98 can support high Voltage power supplies, unlike some of the modern, advanced op-amps.

Brian


On Aug 18, 2018, at 1:11 PM, Jay Schwichtenberg <jschwich53 at comcast.net> wrote:
> While we're talking about S/H here, here's a question.
> 
> Is there any significant advantage over using a 'discrete' S/H circuit
> verses using a chip like the LF398?
> 
> Thanks much.
> Jay S.