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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Final final 1kHz oscillator
Date: Sat, 9 Nov 2024 12:50:30 -0500
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"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.
>>>>
>>>> If a prototype is ever built, attention to the type and quality of the capacitors used will be needed.
>>>> Electrolytics are not intended. Put C1 and C2 near U1 supply pins.
>>>
....
>
> In fact I also had to take out C6 and R9. Once I'd done that the circuit simulated a lot faster, and settled down after about 20 
> seconds. The next 20 seconds showed a third harmonic spike about 60DB below the fundamental - respectable but not great. Putting 
> too much delay into a feedback loop makes it unstable - that's what Bode plots are all about.

There certainly are issues with this circuit despite its ability in simulation to show 80dB down on harmonics.

So perhaps this is not the final final circuit after all.

U2A is not operateing as intended.
C3 can be removed for testing.

>
> -- 
> Bill Sloman, Sydney
>
> --
> Bill Sloman, Sydney
>
>