This is an ajustable power zenner like you ask for. R may be a
potentiometer but must dissipate an important power if you need large
current as 0.5A. It's not a tipical shunt voltage regulator.
If you need to keep at precise value a potential and to use it is not too
good. But if you want only to minimise dissipation power on to a load
( like a serial power supply transistor or something else ) is perfect.
 Vasile

On Thu, 25 Jan 2001, Harold M Hallikainen wrote:

>         This is a current regulator, right? I'm looking for an "adjustable power
> zener", a shunt regulator.
>
> Thanks though!
>
> Harold
>
>
> On Thu, 25 Jan 2001 09:13:50 +0200 Vasile Surducan
> <vasile@L30.ITIM-CJ.RO> writes:
> > lm317 solution: input current to Vi pin, Vout pin connected to A
> > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin,
> > this
> > is also output current.
> >
> > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA
> >
> > Vasile
> >
> > On Wed, 24 Jan 2001, Roman Black wrote:
> >
> > > Harold M Hallikainen wrote:
> > > >
> > > >         I have a project that involves a variable shunt
> > regulator (10-15V,
> > > > 200mA). It SEEMS that it should be possible to use an LM 317 or
> > 337 wired
> > > > in some manner to make this work, but I'm not seeing it. Anyone
> > see how
> > > > this might be done?
> > >
> > >
> > > You can use one transistor and a zener, this works
> > > very well as a shunt regulator as the zener is
> > > driven from the regulated output and gives a
> > > good precise regulation.
> > > -Roman
> > >
> > > --
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> > >
> >
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>
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