The three-terminal positive voltage regulators, such as those in the 78 XX series (where XX is the output voltage), have their maximum current limited to 1 amp. To obtain more current, a PNP power transistor such as 2N2955 can be used, which must be mounted on a good heat radiator. The way to achieve this is shown in the figure. The input voltage must be at least 2 V greater than the desired output voltage, and the regulator must determine the output voltage. The resistors must be wired.
