[sdiy] Cheap low input current opamps?

David G Dixon dixon at mail.ubc.ca
Thu Sep 12 02:11:31 CEST 2013

Thanks for your reply.  Here's my assessment:

Opamp {Typical input offset current/input bias current in pA}:

TL06X {5/30}
TL07X {5/65}
TL08X {5/30}

Hence, it would appear as if either the 06 or the 08 beats the 07.  Here's

LF444 {5/10}

I have used these in my updated CGS ASR design, and no one has complained
about droop.  I think I'll be happy with 06 or 08, but I'd prefer something
a little better.

I'll definitely have a look at the others you mentioned.

> 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.

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