High current 7812 voltage regulator circuit can be constructed by adding a transistor to increase load current capability. As contained in the manual 78/79xx three terminal voltage regulators, positive type of regulator used to use NPN transistors, and otherwise negative type use PNP transistors.
Below is an example of 12V DC voltage regulator circuit using IC 7812 which aims to improve the load current of 1A IC 7812 higher (15A). The more external transistor used the higher load currents.
7812 Voltage Regulator Circuit
The simple voltage regulator circuit below has a current capability up to 15A load by adding three complementary transistors MJ2955. The load current capability can be changed by adding or reducing the number of MJ2955. Resistor 100R or lower can serve to prevent current swamping so as to stabilize the incoming voltage to the IC 7812.
Since 7812 no load current capability greater than 1A needs to be given as a safety fuse 1A output current over the IC, and protect it from high current transients. In IC 7812 and MJ2955 transistor heatsink should be installed so that there is enough heat reduction of the load current is used.
As the above circuit design can be applied to the negative regulator 7912. You need to replace the transistor MJ2955 with other types such as MJ3055, 2N3055 or TIP3055. Hopefully this brief overview is useful in increasing the load current of the 7812 voltage regulator circuit. For Low Dropout voltage - 5V Voltage Regulator Circuit