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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 18:00:01 +0000
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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.

>
>
>>
>>> 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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>>>>WIRE -320 592 -320 496
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