[sdiy] low input bias current opamps

David G Dixon dixon at mail.ubc.ca
Wed Aug 15 10:25:38 CEST 2018

Thanks, Guy!  (Also, thanks Kylee!)

The TI one was great.  The AD one was useless.

The TI one gave up the same perfect opamp I found in H&H -- the OPA404, with
a max input bias current of 4 pA, high supply range, and still great slew
rates.  However, it's $27 on Digikey.  I'm sorry, but I'll die before I pay
$27 for a quad opamp.  The ASR doesn't need to be that non-drifty!  I've had
good luck with TL064 -- maybe I'll just stick with that until I'm feeling
gullible enough to buy more non-refundable LF444s that might be counterfeit.

I'm wondering about CMOS opamps, but many of them don't seem to be able to
operate with +/-15V supplies.  There are a selection that have very low
input currents, but not very high supply voltages.  The CA3140 has nice
specs, but is a single channel.  There doesn't seem to be a quad version.
There is the LMC660, but it doesn't cover the supply range I need.

I have to confess that this is the part of electronics that I hate.  Why are
there a million different opamps, and only one that does what I want that
costs as much as a nice steak dinner?  It's bullshit, actually.  All these
companies should be run outta town by an angry mob.

> -----Original Message-----
> From: Guy McCusker [mailto:guy.mccusker at gmail.com] 
> Sent: Wednesday, August 15, 2018 12:41 AM
> To: David G Dixon
> Cc: SDIY List
> Subject: Re: [sdiy] low input bias current opamps
> I am a long way from knowing what I am doing but when I want 
> to play with devices with specific parameters like this I use 
> the TI parametric search tool.
> http://www.ti.com/amplifier-circuit/op-amps/products.html?pqs=
pocs&familyid=1293#p480=4;4&p1261min=0.9;30&p1261max=30;105> &p2954=PDIP
> Weirdly this doesn't bring up the LF444, I think because that 
> is part of a "specialist" range of devices not covered by 
> this search. Which is annoying.
> Here's a similar search for Analog Devices parts:
> http://www.analog.com/en/parametricsearch/11085#/p2687=|4&p410
> ST have one too but I hate it so I don't use it :)
> On Wed, Aug 15, 2018 at 4:43 AM, David G Dixon 
> <dixon at mail.ubc.ca> wrote:
> > Hey Team,
> >
> > I'm looking for opamps with the following properties:
> >
> > 1) Through-hole
> > 2) Quad opamp
> > 3) 14-DIP package
> > 4) High power range (+/-18V, say)
> > 5) Low input bias current (10 pA or less typical)
> > 6) Pin-compatible with TL074, etc.
> > 7) Not LF444 (cuz they all seem to be defective)
> >
> > So, basically, I'm looking for a suitable alternative for LF444.
> >
> > So, here are my questions:
> >
> > A) Do you know of such a thing
> > B) How does one go about finding such a thing, generally?
> >
> > Thanks in advance!
> > Dave (Floating VCA) Dixon
> >
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> > Synth-diy at synth-diy.org
> > http://synth-diy.org/mailman/listinfo/synth-diy

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