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Path: news.eternal-september.org!eternal-september.org!feeder3.eternal-september.org!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: Low distortion sinewave oscillator without big capacitor. Date: Sat, 5 Apr 2025 16:13:27 -0400 Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com) Lines: 101 Message-ID: <vss2t8$1qhd$1@nnrp.usenet.blueworldhosting.com> References: <vsc420$2ic$1@nnrp.usenet.blueworldhosting.com> <qq8tujlpciqc2jrd0ibljmjr9pd37ip6hi@4ax.com> <vsn5df$o10$1@nnrp.usenet.blueworldhosting.com> <vh9uujhi6chpejn8nfhdh67afc23kfqq32@4ax.com> <vsnufh$2ou7j$1@dont-email.me> <vsp86r$174f$1@nnrp.usenet.blueworldhosting.com> <add0vjdh2gcma0n9pfunq76n04cfbkhtnj@4ax.com> <vspff8$a02$1@nnrp.usenet.blueworldhosting.com> <uop0vjp3d13t441ujfboi5aeeg08anm1je@4ax.com> <vsq9j1$pcn$1@nnrp.usenet.blueworldhosting.com> <tcl2vjp49q4ga21itrpnmr4u3ts06vqffd@4ax.com> Injection-Date: Sat, 5 Apr 2025 20:13:28 -0000 (UTC) Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="59949"; mail-complaints-to="usenet@blueworldhosting.com" Cancel-Lock: sha1:WowRfDd8KDUPwmfdf7o8/9VB/t0= sha256:lXXfRq5Uw0VJBCMDTWlVybkHYmgWLXMdOEdMURnA0+8= sha1:vDOefTcDOyDeT9HqRYN+p6XvQCk= sha256:e5zxAEuFuahGpEo8dGcVJlEbBGISiaFVKna6ydPmdI4= X-MSMail-Priority: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-RFC2646: Format=Flowed; Original X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-Priority: 3 "JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:tcl2vjp49q4ga21itrpnmr4u3ts06vqffd@4ax.com... > On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde" > <invalid@invalid.invalid> wrote: > >>"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uop0vjp3d13t441ujfboi5aeeg08anm1je@4ax.com... >>> On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>> <invalid@invalid.invalid> wrote: >>> >>>>"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:add0vjdh2gcma0n9pfunq76n04cfbkhtnj@4ax.com... >>>>> On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>> <invalid@invalid.invalid> wrote: >>>>> >>>>>>"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vsnufh$2ou7j$1@dont-email.me... >>>>>>> On 4/04/2025 11:33 am, JM wrote: >>>>>>>> On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>> <invalid@invalid.invalid> wrote: >>>>>>>> >>>>>>>>> "JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:qq8tujlpciqc2jrd0ibljmjr9pd37ip6hi@4ax.com... >>>>>>>>>> On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>> <invalid@invalid.invalid> wrote: >>>>>>>>>> >>>>>>>>>>> Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >>>>>>>>>>> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors. >>>>>>>>>>> There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large >>>>>>>>>>> capacitor. >>>>>>> >>>>>>>> You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation). >>>>>>> >>>>>>> Here's my version of John May's variation. >>>>>>> >>>>>>... >>>>>> >>>>>>Yes, that works but only 120dB down at 4KHz. >>>>>>I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens. >>>>>>If it's necessary to wait one minute for the purest tone, that's fine with me. >>>>>> >>>>>>> >>>>>>> Linewraps are going to be a problem - delete all "\n" from the last few lines >>>>>> >>>>>>You don't want to remove \n just remove the wraps. >>>>>> >>>>>>BCM61B does not have two independent transistors. >>>>>> >>>>>>So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well >>>>>>use >>>>>>two >>>>>>of them as shown below. >>>>>> >>>>>>I took the model from >>>>>>https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt >>>>>> >>>>>>It should only be necessary to unwrap the last line of the following. >>>>>>Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar. >>>>>> >>>>>>Version 4.1 >>>>> >>>>> >>>>> Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner. >>>>> >>>> >>>>Wow. That has much lower distortion too. >>>> >>> >>> If you just replace Q1,2 duals with a simple long tailed pair I think >>> you will get better performance. >> >>I'm not sure I understand how the multiplier could be implemented with just a long tailed pair. >> > > Just modulate the tail current and select how much to steer to the > output by directly driving the bases rather than indirectly as in your > circuit. The following link shows one example topology, and a four > quadrant differential I/O version. Compare the linearity of each of > them. > > https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5 Very interesting. Thank you. > > It could be used as shown here. > > https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I Yes that stabilizes, but only 70dB down. > > For best performance use the multplier circuit with differential I/O. > There is already a suitable drive point at U1 in the circuit. > >>The derived circuit below doesn't seem to have any discernible distortion at all as far as I can tell in an LTSpice FFT. >>Not until you get above about 100KHz where it's 160dB down. >> > > Best to use the Hanning windows at these levels if you're not already > doing so.