[sdiy] VCO comparator's reference voltage - rail OK?

cheater cheater cheater00social at gmail.com
Mon Mar 29 00:58:18 CEST 2021


The frequency of your VCO is inverse-linearly dependent on the trip
point of the comparator. Half the trip point = 2x the frequency. 1%
less trip point means pretty much 1% higher frequency, or 17 cents
higher.

On Mon, Mar 29, 2021 at 12:03 AM Neil Harper via Synth-diy
<synth-diy at synth-diy.org> wrote:
>
>
>
> On 3/28/21 5:47 PM, cheater cheater via Synth-diy wrote:
> > On Sun, Mar 28, 2021 at 10:50 PM Neil Harper via Synth-diy
> > <synth-diy at synth-diy.org> wrote:
> >>
> >> i have a drawer full of LM431's so i'll use that unless there's a reason
> >> not to?
> >
> > You don't want an adjustable voltage reference, you want a precision
> > constant voltage reference. Your adjustable voltage ref will be only
> > as good as the resistors you have. So unless you have 0.01%
> > resistors*, in the exact specific values that you need to get the
> > voltage you need, you're out of luck.
> >
> > *needed for 1 cent frequency accuracy
>
> i appreciate the reply cheater, but in this case the lm431 is just
> setting the trip points of the comparator and have no need for .01%
> accuracy here - just stability with unstable rail voltages.
>
>
> --
> /// Neil Harper
> /// Every Wave is New Until it Breaks
>
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