eloso:
so the regulator can be very hot at 700mA? i almost got skin burned when i touched it. Im using tip42c pnp.
Note that my drawing shows both the regulator and pass transistor on the same heatsink. The idea is for both devices to share the same temperature... that way if the pass transistor gets too hot, it heats the 78xx regulator and trips the thermal protection. The circuit is designed to pass along the current limiting and thermal protection of the 78xx regulator to the pass transistor.