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From: Cursitor Doom <cd@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: Final final 1kHz oscillator
Date: Sun, 10 Nov 2024 21:31:31 +0000
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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?
>>>>>
>>>>>Version 4
>>>>>SHEET 1 2196 932
>>>>>WIRE -64 -576 -96 -576
>>>>>WIRE 48 -576 16 -576
>>>>>WIRE 128 -528 112 -528
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