Deutsch English Français Italiano |
<vsu092$14oc7$1@dont-email.me> View for Bookmarking (what is this?) Look up another Usenet article |
Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Bill Sloman <bill.sloman@ieee.org> Newsgroups: sci.electronics.design Subject: Re: Low distortion sinewave oscillator without big capacitor. Date: Sun, 6 Apr 2025 23:40:45 +1000 Organization: A noiseless patient Spider Lines: 585 Message-ID: <vsu092$14oc7$1@dont-email.me> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sun, 06 Apr 2025 15:40:52 +0200 (CEST) Injection-Info: dont-email.me; posting-host="8eec01d14460bffa1e326928b7f8852a"; logging-data="1204615"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+zkgZ33AAIZ6Iqx7KxC6sSK/LjzIL7XHM=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:iiHTQEPiYdRPa8YBnntZb3KWwlc= In-Reply-To: <tcl2vjp49q4ga21itrpnmr4u3ts06vqffd@4ax.com> X-Antivirus: Norton (VPS 250406-2, 6/4/2025), Outbound message Content-Language: en-US X-Antivirus-Status: Clean On 6/04/2025 2:12 am, JM wrote: > 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 > > It could be used as shown here. > > https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I As I've already said, I like it. I've played with it a bit. The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the same emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well. Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with part-to-part variation. I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion. I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful. And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced by the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but something between six and eight looks okay. The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down. Version 4 SHEET 1 3020 2548 WIRE -240 -256 -608 -256 WIRE 480 -256 -160 -256 WIRE -608 -144 -608 -256 WIRE -240 -144 -608 -144 WIRE 80 -144 -160 -144 WIRE -608 -16 -608 -144 WIRE -496 -16 -608 -16 WIRE -352 -16 -416 -16 WIRE -272 -16 -352 -16 WIRE -112 -16 -192 -16 WIRE -64 -16 -112 -16 WIRE 80 -16 80 -144 WIRE 80 -16 0 -16 WIRE 144 -16 80 -16 WIRE 288 -16 224 -16 WIRE 336 -16 288 -16 WIRE 480 -16 480 -256 WIRE 480 -16 400 -16 WIRE -976 0 -1024 0 WIRE -848 0 -912 0 WIRE -1456 48 -1456 16 WIRE -1456 48 -1584 48 WIRE -1584 96 -1584 48 WIRE -1456 96 -1456 48 WIRE -608 96 -608 -16 WIRE -496 96 -608 96 WIRE -112 96 -112 -16 WIRE -64 96 -112 96 WIRE 288 96 288 -16 WIRE 336 96 288 96 WIRE -1024 112 -1024 0 WIRE -976 112 -1024 112 WIRE -848 112 -848 0 WIRE -848 112 -896 112 WIRE -352 112 -352 -16 WIRE -352 112 -432 112 WIRE 80 112 80 -16 WIRE 80 112 0 112 WIRE 480 112 480 -16 WIRE 480 112 400 112 WIRE 512 112 480 112 WIRE -496 128 -608 128 WIRE -64 128 -96 128 WIRE 336 128 304 128 WIRE -96 160 -96 128 WIRE 304 160 304 128 WIRE -1456 224 -1456 176 WIRE -1168 224 -1456 224 WIRE -1024 224 -1024 112 WIRE -1024 224 -1104 224 WIRE -960 224 -1024 224 WIRE -848 240 -848 112 WIRE -848 240 -896 240 WIRE -816 240 -848 240 WIRE -736 240 -752 240 WIRE -608 240 -608 128 ========== REMAINDER OF ARTICLE TRUNCATED ==========