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<p>Not bad! I happen to have a few tubes of TL06x sitting around - a
use for 'em!</p>
<p>CA3140/3130 are still today some of the best for S&H circuits
with just a few pA of input current<br>
</p>
<p>- Oren<br>
</p>
<br>
<div class="moz-cite-prefix">On 4/26/18 11:42 AM, David G Dixon
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:6FC3CF2E745C4488B29EC1209B52F016@galvanox01">
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<div dir="ltr" align="left"><span class="803582516-26042018"><font
face="Arial" size="2" color="#0000ff">Agreed, and agreed.</font></span></div>
<div dir="ltr" align="left"><span class="803582516-26042018"></span> </div>
<div dir="ltr" align="left"><span class="803582516-26042018"><font
face="Arial" size="2" color="#0000ff">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"></span> </div>
<div dir="ltr" align="left"><span class="803582516-26042018"><font
face="Arial" size="2" color="#0000ff">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"></span> </div>
<div dir="ltr" align="left"><span class="803582516-26042018"></span> </div>
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<div dir="ltr" align="left"><font face="Tahoma" size="2"><b>From:</b>
Synth-diy [<a class="moz-txt-link-freetext" href="mailto:synth-diy-bounces@synth-diy.org">mailto:synth-diy-bounces@synth-diy.org</a>] <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>
<blockquote style="BORDER-LEFT: #0000ff 2px solid; PADDING-LEFT:
5px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px" dir="ltr">
<div dir="ltr">
<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" moz-do-not-send="true">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
style="TEXT-TRANSFORM: none; BACKGROUND-COLOR:
rgb(255,255,255); FONT-STYLE: normal; TEXT-INDENT:
0px; DISPLAY: inline; FONT-FAMILY: arial,sans-serif;
WHITE-SPACE: normal; FLOAT: none; LETTER-SPACING:
normal; COLOR: rgb(34,34,34); FONT-SIZE: small;
FONT-WEIGHT: 400; WORD-SPACING: 0px;
font-variant-ligatures: normal; font-variant-caps:
normal; text-decoration-style: initial;
text-decoration-color: initial">low-power</span> - 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>
<div><br>
</div>
</div>
</div>
</div>
</blockquote>
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