With this voltage regulator we can have currents up to 4 A at a 5 V output for TTL circuit power. The transistor can be replaced with equivalents and must be mounted on a good heat heatsink. The suffix H of the integrated circuit means that this component has a metal housing and must be mounted on a small heat radiator. The circuit can be assembled with the 7806 which is most common in our market and with the 2N2955 which is the PNP version of the 2N3055.