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From: john larkin <jl@glen--canyon.com>
Newsgroups: sci.electronics.design
Subject: Re: High purity 1kHz oscillator
Date: Thu, 24 Oct 2024 10:37:29 -0700
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On Thu, 24 Oct 2024 20:39:03 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:

>On 24/10/2024 4:44 am, john larkin wrote:
>> On Tue, 22 Oct 2024 01:10:41 -0400, "Edward Rawde"
>> <invalid@invalid.invalid> wrote:
>> 
>>> But I suspect that component tolerances and mismatched FETs will ruin it.
>> 
>> The very best bulk metal foil resistors have voltage-resistance
>> coefficients of a few ppm/volt. Most resistors are much worse.
>
>Metal film resistors aren't all that much worse than bulk foil 
>resistors, and they are pretty cheap aznd widely available.
>
>> Just the resistors can kill distortion specs.
>
>Not that you can cite an example
>
>> At low frequencies, self-heating and tempco can add distortion too;
>
>Pull the other leg.
>
>> The old HP oscillators
>> had that effect from the lamp filament.
>
>The lamp filaments ran rather hotter.
>
>> DGMS on capacitor nonlinearity.
>The capacitors and resistors would have to remarkably bad to make much
>difference to a well-designed Wein bridge.
>
>You've already got started on making an ass of yourself about resistor 
>non-linearities. Making bizarre claims about capacitors is more of the same.

Gosh, you keep getting nastier and crazier every year. Your only
function now seems to be to generate childish insults aimed at most
everyone.

Here's some C-V notes. Series AC-coupling caps, or caps used in
filters, can introduce distortion too.

https://www.dropbox.com/scl/fo/akiyipqep6n67glfjhcea/ACfQ6By9LRZPKey4tgvpdDE?rlkey=is0vbs7m6xft5u9as5r8eyp30&dl=0

It's sort of outrageous that most ceramic cap data sheets specify
capacitance and voltage and hide the fact that you don't get both.

Film caps can have C-V effects too, and those can matter at PPM
distortion levels.

One could make a parametric amplifier using cap C-V effect.