Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: john larkin Newsgroups: sci.electronics.design Subject: Re: Not particularly low distortion 1kHz sine wave oscillator Date: Sat, 21 Dec 2024 14:49:09 -0800 Organization: A noiseless patient Spider Lines: 37 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Sat, 21 Dec 2024 23:49:10 +0100 (CET) Injection-Info: dont-email.me; posting-host="5ae8e2477a95e38eca0a8da9df798e27"; logging-data="280410"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/Fk70TgpH/QDLCfwc2yZ0K" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:sFaORcLrJZ0khkQ36GPNR/3C+f4= Bytes: 2811 On Wed, 4 Dec 2024 14:10:17 -0500, "Edward Rawde" wrote: >"Bill Sloman" wrote in message news:viot8j$mt28$1@dont-email.me... >> On 4/12/2024 4:29 pm, Edward Rawde wrote: >>> "Bill Sloman" wrote in message news:viokrg$l9s1$1@dont-email.me... >>>> Edward Rawde has posted a number of low distortion 1kHz sine wave oscillators as LTSpice simulation, and John May has posted a >>>> couple of much low distortion examples. >>>> >>>> As designs they are bit opaque. I've posted my own attempts. >>>> >>>> Here's another. >>> >>> Are you sure that's the correct circuit Bill? >>> >>> What I'm seeing has U1 displaced but easy to correct but U2 output is not connected and the feedback from U5 is hanging in mid >>> air >>> above an unconnected current mirror with nothing connected the the FET gate circuit. >> >> It probably isn't. Here's much the same circuit tweaked to give the 1kz fundamental closer to 0 dB - 1V rms. The extra componets >> are R8, R9 and R28 at the top right of the circuit. >> > >Ok I had to adjust the position of U1 and connect the + pin. >FFT shows noise at 70dB down. > >I decided to find out whether a discrete circuit using a high voltage rail would have better distortion performance. >This circuit has no gain control yet but if you take a sample when the output is at about 1V pk-pk you get 100dB down at 2kHz as >long as you keep your fingers away from the supply rail. If I could just get rid of 2kHz it would be 130dB down. > A good loop gain scheme could use a pair of jfets or mosfets connected antiparallel against ground, gates tied together to the control voltage. Nonlinearities would mostly cancel.