[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.
> 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:
> 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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