<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="">Hi Chris,<div class=""><br class=""></div><div class="">I’ve seen various approaches to this problem including:</div><div class=""><br class=""></div><div class="">1) Half-wave precision rectifiers to remove inputs below zero volts, with zeners or similar to limit the highest voltage</div><div class=""><br class=""></div><div class="">2) Op-amp clipping with op-amps run from +/-12V that then have their maximum output scaled down and offset to the correct range.</div><div class=""><br class=""></div><div class="">3) Op-amp clipping on single-ended op-amps run at the processor voltage (like yours)</div><div class=""><br class=""></div><div class="">I’m sure there are others. Honestly, I think (3) is pretty simple and straightforward, although I like the precision rectifier circuit too (just because it’s cool!) but the limitation there is that it doesn’t control the higher voltage as neatly.</div><div class=""><br class=""></div><div class="">I notice you have the MCP6002 on 5V supply, but you said you wanted 0-3.3V output. Is that right?</div><div class="">100K input impedance is typical for CV inputs on modular gear, so you might want to double your resistor values round the op-amp.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">HTH,</div><div class="">Tom</div><div class=""><br class=""><div class="">
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<div><br class=""><blockquote type="cite" class=""><div class="">On 4 Dec 2020, at 13:31, Christian Maniewski via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""> <title class=""></title> <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no" class=""> <div style="font-family: Helvetica; font-size: 13px;" class=""><img id="75E3E7C7EDA0AF42FB4C4E434016155C" width="0px" src="https://read-receipts.canarymail.io:8100/track/C49266956199D83F011285EF840B71C7_75E3E7C7EDA0AF42FB4C4E434016155C.png" height="0px" class=""> <div id="CanaryBody" class=""> <div class=""> Hi all!</div><div class=""><br class=""></div><div class="">I’m trying to come up with an op-amp design for a CV input. I want to transform a signal ranging from -5V to +7V to a more MCU digestable 0-3.3V. I came up with the circuit you’ll find attached.</div><div class=""><br class=""></div><div class="">I have seen other approaches, where an offset reference is injected in the feedback loop, while the positive op-amp input is grounded. Are there any disadvantages to my approach or is it also valid?</div><div class=""><br class=""></div><div class="">Thank you so much!</div><div class=""><br class=""></div><div class="">I’ve been following this email list for some time now. This is my first question and first email entirely. Please bear with me.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Chris</div> <div class=""><br class=""></div> </div> <div id="CanarySig" class=""> <div class=""> <div style="font-family:Helvetica;" class=""><div style="font-family:Helvetica;" class=""><br class=""></div></div> <div class=""><br class=""></div> </div> </div> <div id="CanaryDropbox" class=""> </div> </div><span id="cid:A8A35FDA-4568-436B-ADF2-C29FA227DEA2"><cv_in.pdf></span>_______________________________________________<br class="">Synth-diy mailing list<br class=""><a href="mailto:Synth-diy@synth-diy.org" class="">Synth-diy@synth-diy.org</a><br class="">http://synth-diy.org/mailman/listinfo/synth-diy<br class="">Selling or trading? Use marketplace@synth-diy.org<br class=""></div></blockquote></div><br class=""></div></body></html>