<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">Yes, I agree! So we’ve found two examples for you, Didier! Phasers and OTA filters both use the OTA like a variable resistance.</div><div class=""><br class=""></div><div class="">Tom<br class=""><div class=""><br class=""><div class="">
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<div><br class=""><blockquote type="cite" class=""><div class="">On 9 Feb 2020, at 12:16, Richie Burnett <<a href="mailto:rburnett@richieburnett.co.uk" class="">rburnett@richieburnett.co.uk</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">The OTA acts as a variable resistor here:<br class=""><br class=""><a href="https://electricdruid.net/wp-content/uploads/2017/04/CEM3320LowpassFilterStage.png" class="">https://electricdruid.net/wp-content/uploads/2017/04/CEM3320LowpassFilterStage.png</a><br class=""><br class="">-Richie,<br class=""><br class=""><br class=""><br class="">-----Original Message----- From: Tom Wiltshire<br class="">Sent: Sunday, February 09, 2020 11:40 AM<br class="">To: Didier Leplae<br class="">Cc: Synth DIY<br class="">Subject: Re: [sdiy] LM13700 as VC resistor<br class=""><br class="">OTA-based phaser designs are about the only application I can think of where the OTA functions like a resistor rather than a VCA. Even then it’s perhaps arguable.<br class=""><br class="">Have a look at schematics for the EH Small Stone and the many subsequent derivatives.There’s also a good explanation on R.G.Keens page about phasers:<br class=""><br class="">http://www.geofex.com/article_folders/phasers/phase.html<br class=""><br class="">HTH,<br class="">Tom<br class=""><br class=""><br class="">==================<br class=""> Electric Druid<br class="">Synth & Stompbox DIY<br class="">==================<br class=""><br class=""><br class="">On 8 Feb 2020, at 09:58, Didier Leplae via Synth-diy <synth-diy@synth-diy.org> wrote:<br class=""><br class=""><br class="">I am curious to know anyone’s opinions on using the LM13700 as a voltage controlled resistor.<br class=""><br class="">The LM13700 datasheet has a couple schematics which I have tried building, with mixed results. I’m having a hard time knowing what sort of resistance I am getting as the multimeter gives strange and inconsistent readings.<br class=""><br class="">The information on the datasheet is somewhat incomplete in my opinion and it is not easy to find much info online either.<br class=""><br class="">It doesn’t seem like it is common practice to use these as VC resistors. Is that because it doesn’t work very well? Or use too many parts?<br class=""><br class="">Any insight on this would be appreciated.<br class="">I’m interested mostly in the single ended schematic at the moment.<br class=""><br class="">Thank you,<br class=""><br class="">Didier<br class=""><br class=""><br class=""><br class="">_______________________________________________<br class="">Synth-diy mailing list<br class="">Synth-diy@synth-diy.org<br class="">http://synth-diy.org/mailman/listinfo/synth-diy<br class=""><br class=""><br class=""><br class="">Virus-free. www.avg.com<br class=""><br class=""><br class=""><br class=""><br class=""><br class="">_______________________________________________<br class="">Synth-diy mailing list<br class="">Synth-diy@synth-diy.org<br class="">http://synth-diy.org/mailman/listinfo/synth-diy <br class=""></div></div></blockquote></div><br class=""></div></div></body></html>