<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Apr 17, 2020, at 2:12 PM, David G Dixon <<a href="mailto:dixon@mail.ubc.ca" class="">dixon@mail.ubc.ca</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I've used Thomas Henry's version of the two-transistor sine shaper in all my<br class="">VCO designs for years (and did a bit of an optimization study to confirm<br class="">that his resistor values were indeed optimum). Simulation suggests that I<br class="">can get as low as 0.57% THD with that shaper, and there is no visual<br class="">evidence of the triangle apex leaking through. At that level, there is<br class="">virtually no aural evidence that it isn't a pure sine wave.<br class=""><br class="">How much better is this new shaper in terms of THD? (If no one answers, I<br class="">guess I could simulate it myself.)<br class=""></div></div></blockquote><div><br class=""></div><div><br class=""></div><div>The spectrum plots in my article show this. </div><div><br class=""></div><div>For the mathematical tsin() curve, the third and fifth harmonics are down 76dB. So that should be below 0.05% distortion. </div><div><br class=""></div><div>For the Spice simulated example circuit with two transistors and fixed EIA resistor values, the harmonics are well below 60dB down, so that would be about 0.12% distortion.</div><div><br class=""></div><div>Gettin' tough to measure. </div><div><br class=""></div></div><div class=""><div style="color: rgb(0, 0, 0); font-family: Menlo; 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-size-adjust: auto; -webkit-text-stroke-width: 0px;"> -- Don<br class="">--<br class="">Donald Tillman, Palo Alto, California<br class=""><a href="http://www.till.com" class="">http://www.till.com</a></div>
</div>
<br class=""></body></html>