On Mar 21, 2011, at 6:48 AM, Olin Lathrop wrote:

> If you're going to go so far as adding a opamp to control the LM317, =20
> you
> might as well just have the opamp drive something like a PNP pass
> transistor.  The fancy electronics in the LM317 isn't doing much for =20
> you at
> this point.  You're mostly using the LM317 as a pass element anyway.

A *fancy* pass element with features like overcurrent and overtemp =20
shutdown.  And pretty cheap, too.

I have a desire to build a general purpose lab-style power supply =20
using multiple 317s.  Several in parallel for increased output.  One =20
for the negative-voltage-driven current source that permits voltages =20
below 1.25V.  Maybe one as the regulation element in a switching pre-=20
regulator.  Probably because of that eBay deal I got on a box of =20
317s... :-)

BillW

--=20
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