[sdiy] Cheap low input current opamps?

[rsdio at sounds.wa.com]

I have shipped commercial products with S&H based on the OPA4374 (0.5  
pA) and TLV2374 (1 pA), but those are more expensive than the LF444.

Looking back at my selection notes, I considered the LM224D, TL084CD,  
TL074CD, LF353MX, LMV324I, LF347D, OPA4348, and compared them all to  
the venerable S&H LF398. Of those, the TL084 might meet your  
specifications, and it's been used in classics like the Prophet 5  
(IIRC).

Your best choice might be the OPA4348. It's cheaper than the LF444  
and has typical offset and bias currents of only 0.5 pA.

Brian Willoughby
Sound Consulting


On Sep 11, 2013, at 11:19, David G Dixon wrote:
> I'm looking for a cheap alternative to the LF442/LF444 opamps,  
> which have
> very decent input current specs and therefore recommend themselves  
> for use
> as S&H buffers (typical offset current 5 pA, typical bias current  
> 10 pA).
> I'm coming up short with Google searches.  Does anyone here have any
> suggestions?  The TL06X series is pretty good with typical bias  
> current of
> 30 pA, but I'm not finding anything else that isn't much more  
> expensive.