<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr">R values around 100k or so give a good compromise between noise and power consumption.</div><div dir="ltr"><br></div><div dir="ltr">Ian</div><div dir="ltr"><br><blockquote type="cite">On Nov 13, 2020, at 9:59 AM, tpuefke via Synth-diy <synth-diy@synth-diy.org> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">I was hoping someone more experienced could help shine some light on this issue. This is still quite puzzling to me as a non-engineer.<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">Looking through my collection of schematics from various places like MFOS (bless his soul), I see a lot of the standard 100k resistor in negative feedback op-amp configuration, for inverters, mixers, attenuators... For a long time i have been adapting these as my go-to values without giving it much thought and usually it works pretty well. The odd schematic here and there uses lower values.<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><div style="width: 100ch; word-wrap: break-word; word-break: break-word;">Considering that high feedback resistance implies a higher gain potential, shouldn't lower values (e.g. 10k, 1k even) usually be a better choice in terms of circuit stability? <br></div><div style="width: 100ch; word-wrap: break-word; word-break: break-word;">Or is this a non-issue for fractional gain setups? <br></div><div><br></div></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">I've been wondering about this for a while now and recently stumbled across this post discussing Rf values and op-amp input capacitance:<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><div style="width: 100ch; word-wrap: break-word; word-break: break-word;"><div style="width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="width: 100ch; word-wrap: break-word; word-break: break-word;"><a href="https://www.analog.com/en/analog-dialogue/raqs/raq-issue-122.html" style="color: rgb(45, 113, 184);">https://www.analog.com/en/analog-dialogue/raqs/raq-issue-122.html</a><br></div><div><br></div><div><br></div><div>What are the pros and cons in your experience for using high resistances like these, in attenuator / unity inverter setups especially? <br></div></div></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">Higher resistances simply to reduce current consumption in bigger circuits? What about resistor noise?<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">Just trying to wrap my head around this to be able to make more informed decisions. <br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">Any feedback is HIGHly appreciated. :)<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">thanks,<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;">Tom<br></div><div style="color: rgb(60, 60, 60); font-family: monospace; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; width: 100ch; word-wrap: break-word; word-break: break-word;"><br></div><div><br></div><span>_______________________________________________</span><br><span>Synth-diy mailing list</span><br><span>Synth-diy@synth-diy.org</span><br><span>http://synth-diy.org/mailman/listinfo/synth-diy</span><br><span>Selling or trading? Use marketplace@synth-diy.org</span><br></div></blockquote></body></html>