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<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
size=2 face=Arial>Agreed, and agreed.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
size=2 face=Arial>I have made a (somewhat well known) version of the CGS analog
shift register for quite a few people, with a number of improvements over the
original. I had traditionally used LF444 for the S&H buffers because
of its low input bias current (typically 10 pA). However, recently, I
bought a number of them from a local shop (they had been sourced from Digikey),
and they turned out to be defective (or counterfeit -- I'm not sure, they just
don't work). Out of desperation, I ended up using a TL064 instead (typical
IBC 30 pA, compared to 65 pA for TL074) because that was the next best thing I
had in my stores, and it worked like a dream. Very little S&H drift,
even in "loop" mode (where the same three stored voltages are looped around the
ASR outputs over and over). I use 0.1uF caps in these S&H circuits, so
30 pA generates very little drift (about 300 uV/s, which I guess I can live
with).</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
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<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
size=2 face=Arial>So now, TL064 is my standard opamp for those buffers.
Maybe one of these days I'll look for a relatively inexpensive quad with really
low IBC (1 pA or less) -- anybody have any suggestions?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=803582516-26042018><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
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<DIV dir=ltr align=left><FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of </B>Mattias
Rickardsson<BR><B>Sent:</B> Thursday, April 26, 2018 2:54 AM<BR><B>To:</B>
Michael E Caloroso<BR><B>Cc:</B> SDIY List<BR><B>Subject:</B> Re: [sdiy]
Happenin' new opamp<BR></FONT><BR></DIV>
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<DIV class=gmail_extra>
<DIV class=gmail_quote>On 25 April 2018 at 06:15, Michael E Caloroso <SPAN
dir=ltr><<A href="mailto:mec.forumreader@gmail.com"
target=_blank>mec.forumreader@gmail.com</A>></SPAN> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>The input offsets - hence CV error and drift - are
temperature<BR>dependent. A substrate quad is going to generate more
heat than a<BR>single or dual.<BR><BR>There's a reason you see single opamps
on the input stages of VCOs.<BR></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>Ah, thanks for pointing that out.</DIV>
<DIV><BR></DIV>
<DIV>Speaking of CV and favourite op-amps, I prefer using TL064 for CV
multiplexing. They are quad, but <SPAN
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so they keep cool.</DIV>
<DIV><BR></DIV>
<DIV>When I come to think of it... I also very much prefer quads due to them
having the outputs on the corner pins. Very easy to probe and measure on. It's
a pity that the dual op-amps got the pinout they got, with an output on pin 7.
:-)</DIV>
<DIV><BR></DIV>
<DIV>/mr</DIV>
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