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</o:shapelayout></xml><![endif]--></head><body lang=FR-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-CA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I think this added Schottky diode could protect U12D’s input..<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It has around 0.3v of forward voltage (conducting before 74HC’s 0.6v internal input diode)<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>and 200mA max of forward current (when C11 discharges to +5v).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Schottky diode..<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><img width=493 height=264 id="Image_x0020_1" src="cid:image004.jpg@01D69FC1.6DEB9AF0"></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=FR style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>De :</span></b><span lang=FR style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Didrik Madheden [mailto:nitro2k01@gmail.com] <br><b>Envoyé :</b> 9 octobre 2020 10:59<br><b>À :</b> Jean-Pierre Desrochers<br><b>Cc :</b> SDIY List<br><b>Objet :</b> Re: [sdiy] Capacitor type matters in 74HCxx one-shot circuit ?<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>The two parameters that could matter are frequency response (self-inductance) and leakage current. <o:p></o:p></p><div><p class=MsoNormal>Frequency response doesn't really matter. It's just passing a pulse through the capacitor and waiting for the capacitor to charge and flip back. It's very noncritical.<o:p></o:p></p></div><div><p class=MsoNormal>Leakage current doesn't really matter either. Both sides are driven at all times, so you're not relying on the capacitor to hold it's charge for long periods like in for example a sample and hold circuit.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Something else about the circuit however, is that during the reset phase U1's output will go high while the capacitor is charged. This will cause the voltage at U2's inputs to go above the usual maximum voltage and discharge the capacitor through the chip's protection diodes. This may or may not be ok in practice but something to be aware of.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>/Didrik<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Fri, 9 Oct 2020 at 16:42, Jean-Pierre Desrochers <<a href="mailto:jpdesroc@oricom.ca">jpdesroc@oricom.ca</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-CA>Does the capacitor type (Ct: ceramic or film) matter in a circuit like this one ?</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-CA>I’d say film is obviously better but.. in such a circuit… ??</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><img border=0 width=506 height=230 id="gmail-m_-8135044707607254865Image_x0020_1" src="cid:image003.png@01D69FC0.9BEB61C0"><o:p></o:p></p></div></div><p class=MsoNormal>_______________________________________________<br>Synth-diy mailing list<br><a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a><br><a href="http://synth-diy.org/mailman/listinfo/synth-diy" target="_blank">http://synth-diy.org/mailman/listinfo/synth-diy</a><o:p></o:p></p></blockquote></div><p class=MsoNormal><br clear=all><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>