How to choose darligton pair...??

[aniket433]

i m designing 0-35 v & 5 Amp linear power supply. for this configuration i m selecting LM317 with darligton pair ( for current boosting)
then which specific darligton pair ic i should select..? :-?

 

[dick_freebird]

I've seen app notes suggesting a single PNP for the booster,
an NPN Darlington would impose additional headroom and
biasing circuitry I expect. Look at the National datasheets
and app notes for the LM117/317 and you'll find schematics.

At 30V drop and 5A, you'll be primarily interested in getting
the heat out - electrical performance is not the #1 difficulty.
You may want multiple, ballasted pass devices and forced
air cooling, or at least decent through-case convection and
a whole lot of fins.