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Path: ...!weretis.net!feeder9.news.weretis.net!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: Fri, 4 Apr 2025 23:55:11 -0400 Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com) Lines: 511 Message-ID: <vsq9j1$pcn$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> Injection-Date: Sat, 5 Apr 2025 03:55:13 -0000 (UTC) Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="26007"; mail-complaints-to="usenet@blueworldhosting.com" Cancel-Lock: sha1:/0kr5i8ubxo+vnnGZbAG8akZKks= sha256:6yz/l0QZS+XZkgq+/dS8sj+iAQrgaozKLETHRy0eHBY= sha1:xs7lsTZP0htWVSsekKUXRCT7bRM= sha256:qE+/aW+MeiXb0Q1cyYpeMAvRzCikmElojiu9Kcvu1mc= X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-RFC2646: Format=Flowed; Original X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-Priority: 3 Bytes: 15198 "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. 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. 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