<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="">At the simplest level, it’s a trade-off between current and noise. Lower value resistors generate less noise, but use more current (and provide lower input impedance) and higher value resistors do the reverse. So you tend to see “compromise” values around 10K-100K. 1Meg is getting “big” and 1K or less is getting “small”.<div class=""><br class=""></div><div class="">Years ago I had the same question and since the internet didn’t exist yet, I did some experiments on my breadboard with a 741 and discovered that 1M upwards was noticeably noisier, but that anything between a few K and a few hundred K didn’t really seem to make much odds.<br class=""><div class=""><br class=""></div><div class="">Tom</div><div class=""><br class=""><div class="">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: 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;">==================<br class=""> Electric Druid<br class="">Synth & Stompbox DIY<br class="">==================</div></div>
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<div><br class=""><blockquote type="cite" class=""><div class="">On 30 Dec 2019, at 13:17, bbob <<a href="mailto:fluxmonk@gmail.com" class="">fluxmonk@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">(please excuse the noobiness).... <div class=""><br class=""></div><div class="">in a basic inverting op-amp circuit, where the input and feedback resistors are equal, the gain will be -1... but what are the pros/cons that determine the choice resistor value? i commonly see/have used 1k, 10k, 47k, 100k in synth circuits, but what design considerations drive those choices of values? my immediate application is basic output buffers on a LFO, and 1k seems to be working fine, but it got me to thinking (uh oh).</div><div class=""><br class=""></div><div class="">thx, b</div></div>
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