lol i'd use a resistor (always do).. i was thinking in theory (to power a device which required more amps than i have, but using this method i could get a regulated 5v (current from the higher voltage rail) out power what i want... surely this way would be better than a 5 watt zener diode? (rated at 5v) vs a Tip31 and the above method?.. powering a 1amp 5v usb device from 12v via a resistor and 5v on the base pin, i still have issues with this (yes yes with a resistor to limit the current....)