Re: Sinewave oscillator without gain control.

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...

On 24/01/2025 5:02 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...

On 24/01/2025 11:14 am, Edward Rawde wrote:

Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
an
oscillator which does better than that when it passes through the required output level.

>
This is obviously true. Why do you think you need to tell us about it?
>

>
You do make me laugh sometimes Bill.
Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

>
I never said it did. I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.
>

Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

>
Then you haven't looked at the current waveform going through the the FET.
>

So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
than 120dB.

>
And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug. That might explain why your
simulations of my circuit run a thousand times slower for you than they do for me and a couple of other people.

LTSpice 24.1.1 is now available.
The circuit below produces a 24mV pk-pk sineish wave at 23 MHz on my installation of LTSpice 24.1.1 with all component updates.
FFT shows 23 MHz at -40dB
Simulation speed is about 115 us/s
I didn't simulate beyond 2.5 ms

Simulation in LTSpice 24.0.12 shows pretty much identical behaviour but the simulation speed is slower at about 75us/s.

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TEXT -1248 -1352 Left 2 !.tran 0 10s 0s startup