Re: Not particularly low distortion 1kHz sine wave oscillator

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.
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As designs they are bit opaque. I've posted my own attempts.
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Here's another.

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Are you sure that's the correct circuit Bill?
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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.

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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.
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Ok I had to adjust the position of U1 and connect the + pin.
FFT shows noise at 70dB down.
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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.