Re: gEDA-user: Dropping a few volts

[phil@xxxxxxxxxxxxx]

> So why not use a standard-issue three-terminal adjustable regulator
> circuit?  Those things don't care what Vin is, only Vin-Vout.

If your Vo is driving a big cap you'll end up with vin = unloaded input
voltage and Vo=0V at turn-on.  This could exceed max ratings at a bad time
which is at max current--charging a big cap.

I don't remember how stable your load will be.  If it is pretty stable,
you could just use a series zener on the high side of your regular
regulator.  I'm rebuilding some old equipment at the moment that does this
to drop +/-24 down to +/-12V on a bunch of chips that have max rails
voltages of +/-12V.  It's obvious the rails are not all that stable and do
exceed the max rating.  But this stuff has been working for almost 40
years ... and the chips all rely on supply rejection.

Phil



>
> Duh!
>
> Thanks for the help, even if you didn't realize what answer you were
> really giving.  ;)
>
> --
> Randall
>
>
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> geda-user@xxxxxxxxxxxxxx
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>




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