<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr">Agree with all that! But there have been some pretty wild variation between manufacturers and batches as far as matching and variation with Iabc. I went so far as to make up a test measurement jig, characterizing dozens of chips and labeling them for future use. What was tough was finding devices where both sides were good enough.</div><div dir="ltr"><br></div><div dir="ltr">Ian</div><div dir="ltr"><br><blockquote type="cite">On Oct 28, 2020, at 2:39 PM, Phillip Gallo <philgallo@gmail.com> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr">I have built VCAs using the LM3700 in a differential configuration. They all worked well. <div>Back when; I had been told the matching of the amplifiers was overstated in the spec sheet but found it to be accurate for the chips i had available.<div><br></div><div>I didn't use the Darlingtons instead using I/V op-amps into Diff amp config. I also used trimmers and this paid-off nicely. If you don't use linearization you can exploit the "3080-ish" overdrive wave shaping with higher S/N. With linearization, the VCA's were quite clean, ready to compete with alternate solutions.</div><div><br></div><div>p</div><div><br></div><div><br></div><div><div><br></div><div><br></div><div><div><br></div></div></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Oct 27, 2020 at 3:37 PM Eric Schlappi <<a href="mailto:eric.schlappi@gmail.com" target="_blank">eric.schlappi@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>@aaron That's the paper I was talking about, thanks for linking it into the discussion!</div><div><br></div><div>@Ian Looking at the wrong things I guess! I only remember seeing it (well... the 3080) used with differential input as the VCA in the radioshack mg-1, and that's presumably because the filter output is differential.</div><div><br></div><div>Thanks again, I guess I'll keep on using balanced inputs for OTAs but won't get rid of the trimmers.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Oct 27, 2020 at 2:01 PM Ian Fritz <<a href="mailto:ijfritz@comcast.net" target="_blank">ijfritz@comcast.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
> On Oct 27, 2020, at 2:18 PM, Eric Schlappi <<a href="mailto:eric.schlappi@gmail.com" target="_blank">eric.schlappi@gmail.com</a>> wrote:<br>
> <br>
> <br>
> You guys are right.<br>
<br>
Why, thank you! Please bear in mind that a number of us guys have worked with these chips since they first came out in 1979.<br>
<br>
> I guess I was wondering why I don't see the lm13700 used with differential input more often, or am I still missing something?<br>
<br>
I’ve always used balanced inputs for mine in everything I have ever built, except when they are used as switches.<br>
<br>
Dunno what you have been looking at; this is pretty standard as far as I know.<br>
<br>
Ian<br>
> <br>
<br>
</blockquote></div>
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