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Path: ...!weretis.net!feeder9.news.weretis.net!panix!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!nnrp.usenet.blueworldhosting.com!.POSTED!not-for-mail From: "Edward Rawde" <invalid@invalid.invalid> Newsgroups: sci.electronics.design Subject: Re: High purity 1kHz oscillator Date: Tue, 22 Oct 2024 14:21:08 -0400 Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com) Lines: 37 Message-ID: <vf8qel$ca7$1@nnrp.usenet.blueworldhosting.com> References: <vf7c4h$1m5m$1@nnrp.usenet.blueworldhosting.com> <vf7slm$1e357$1@dont-email.me> <vf8bs8$27n8$1@nnrp.usenet.blueworldhosting.com> <91qfhj1tbi1ouh0cihrsjghk1q0t9ke345@4ax.com> Injection-Date: Tue, 22 Oct 2024 18:21:09 -0000 (UTC) Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="12615"; mail-complaints-to="usenet@blueworldhosting.com" Cancel-Lock: sha1:MuMu0FBH9nViSS5xc+KXO7WZ3pw= sha256:CcdeRvlG4/rmhTfn7mvHSsfu/AdklBmsqCko4MOZv3I= sha1:JtT2cY2EbPjF0tDn2Yn0L7U425s= sha256:hY+X01k+fFubwELTbRbY4GZOY9w5zaYxaFW1bhI33FI= X-RFC2646: Format=Flowed; Original X-MSMail-Priority: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-Priority: 3 Bytes: 2942 "john larkin" <jl@glen--canyon.com> wrote in message news:91qfhj1tbi1ouh0cihrsjghk1q0t9ke345@4ax.com... > On Tue, 22 Oct 2024 10:12:23 -0400, "Edward Rawde" > <invalid@invalid.invalid> wrote: > >>"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vf7slm$1e357$1@dont-email.me... >>> On 22/10/2024 4:10 pm, Edward Rawde wrote: >>>> But I suspect that component tolerances and mismatched FETs will ruin it. >>>> >>>> Otherwise it should be easy to get 60dB down on unwanted harmonics with a better filter. >>>> >>>> FWIW I likely won't be here for the next week. >>> >>> <snip> >>> >>> My message was that the current sucked out of U2 through D1 and D2 was a narrow spike, peaking at 0.3mA and repeating at 1kHz, >>> which distorted the voltage at the output of U2. >>> >>> Your revised circuit persists with this mistake, and the filter you've added around U1 doesn't do enough to compensate. >> >>That's what I thought you'd say, because there are now two spikes, but it does seem to reduce distortion. >>So I'd leave it in any experimental prototype and take the decision to remove it if real testing shows it's not sufficiently >>beneficial. >>The filter can be redesigned when a real circuit is tested. I didn't have time to do a more elaborate active filter. > > If you do build an ultra-low-distortion oscillator, how would you > measure the distortion? I'd probably ask the designers of the circuit Bill Sloman referenced, how they measured -110dB https://www.analog.com/media/en/technical-documentation/application-notes/AN132f.pdf I'd be happy with 70dB but I doubt that's achievable with the FET circuit. > >