Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: john larkin <JL@gct.com>
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: <u7hemjh2rvh051e8boeun97t9fe7ah4hm3@4ax.com>
References: <viokrg$l9s1$1@dont-email.me> <viopbu$1483$1@nnrp.usenet.blueworldhosting.com> <viot8j$mt28$1@dont-email.me> <viq9em$2v5p$1@nnrp.usenet.blueworldhosting.com>
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"
<invalid@invalid.invalid> wrote:

>"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viot8j$mt28$1@dont-email.me...
>> On 4/12/2024 4:29 pm, Edward Rawde wrote:
>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viokrg$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.