I would like some quick advice. First of all, please no "why do you want to do that" or "use a switcher" or any other things that are not what I asked.
With that, please see the attached circuit diagram. It is a simple and very nicely performing voltage regulator.
The idea behind it is that the LM-317 initially provides the output, but as soon as the current demand increases enough, the voltage across the PNP Vbe makes the transistor begin to conduct and it "pushes in" the required extra amount of current to maintain the LM-317 programmed voltage.
By adding one or more NPN transistors to the circuit making a "PNP-NPN Darlington", any amount current can be provided, and always perfectly referenced to the LM-317. The way the 317 is wired allows it to sense any drop along the path (up to the point where it's connected) allowing for remote voltage sense if desired.
My question / advice request is: If I wanted to replace the NPN "boosters" or even just the main PNP transistor with a MOSFET or IGBT, which would be preferable, and why? Or, are neither suitable substitutes for BJT parts?
My thinking is that maybe MOSFET parts would be more rugged and less likely to be damaged by temporary (fraction of a second) overloads. Of, course, I'm probably way out in left field about this...
(click thumb for full size)