Re: Final final 1kHz oscillator

On Sun, 10 Nov 2024 18:00:01 +0000, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 10 Nov 2024 17:45:00 +0000, Cursitor Doom <cd@notformail.com>
wrote:
>

On Sun, 10 Nov 2024 12:12:34 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Cursitor Doom" <cd@notformail.com> wrote in message news:bs81jjt7d064jc1ktmvihgn30qkhf67taj@4ax.com...

On Sun, 10 Nov 2024 00:49:36 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vgnkgg$3p31a$1@dont-email.me...

On 9/11/2024 7:39 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vgn4gm$3lcor$1@dont-email.me...

On 9/11/2024 7:43 am, Edward Rawde wrote:

This is the simplest circuit I can come up with.
Harmonics are more than 80dB down in simulation.
FFT the last 30 seconds.
There is only one harmonic stopping me claiming 90dB but the exact FFT result can depend
on exactly how much output is selected for the FFT. You may see different results.
>

>
I have fixed my circuit but it raises more questions than it answers.
This circuit deliberately has no text and no u symbols so should be ready to simulate.
If you let it complete (about 20 minutes on a fast PC) the FFT should show at least 80dB purity and there aren't many harmonics
standing in the way of 90dB.
Startup isn't fast and it takes at least 20 seconds of simulation to fully settle.

>
Spectral purity might be fine for all I can tell but the output
amplitude is all over the place,

>
Change R9 to 1.07Meg does it amplitude stabilize now?
Adjustment will be needed in any real circuit.

>
Indeed, but for a simulation we should be seeing identical results!
I've made the change as you suggested and it's increased the sim time
considerably. I'll post again when it's completed.

>
Update: looking *much* better at 25% done. Settled after 7.5s. I will
let it run its course anyway and post again at the end with the final
outcome.

Looks really stable now; 4.5V peak to peak and none of the
fluctuations of the earlier simulations. Weird how it took *so* much
longer to complete this time,  though.

>

>
>

>

even if the sim is left to run its
full course. Also, what's the purpose of the 6 diodes in series at the
top of the schematic? If you need to drop 4V there ought to be a more
elegant way of doing it!
>
>
>

There are two things I don't understand about my own circuit.
>
1. Why does LT1678 work fine in position U2 but LT1057 does not.
2. Why is the DC stabilization circuit (U3 and associated components) needed and would it work just the same in reality?
>
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TEXT -624 272 Left 2 !.tran 0 150s 0s startup
 

>