So for a power supply project I need a voltage regulator giving me a positive output at around 40v. Obsessively you can not buy these, So i am useing a circuit which consists of a resistor, npn transistor, and zener diode. the positive input goes to the collector of the transistor and through the resistor to the base of the transistor, and a zener diode of 39v is on the base to ground. Then my output is the emitter. This works fine, but... As some of you may know I do a lot in audio and need a negative voltage regulator for the split audio power supply, is there a modification I need to do to make this the same thing just as a negative voltage regulator? Also what the heck does a negative voltage regulator do anyway? I understand a positive obsessively but am not sure about the negative.