Fixed 5 V rail in a TO-3 can
The STMicroelectronics L7805CT is a single-output positive fixed 5 V linear regulator in the TO-3 steel can. It delivers up to 1.5 A continuous with a typical dropout of 2 V at 1 A load. The 62 dB PSRR at 120 Hz attenuates mains ripple, adequate for general-purpose analog and logic supplies.
Dropout headroom and thermal budget
The 2 V dropout at 1 A sets a minimum input-to-output differential of 2 V; below that the regulator drops out of regulation. At 1.5 A output and a 7 V input (2 V dropout), the TO-3 package dissipates about 3 W. The steel can requires a heatsink — in still air the junction-to-ambient thermal resistance of the TO-3 alone is around 35–40 °C/W, which would exceed the 125 °C maximum junction temperature at that dissipation. A clip-on or bolt-on heatsink is mandatory for full-rated current. The quiescent current is 8 mA typical, which is modest for a 1.5 A linear regulator but adds to the total input current budget in battery-powered designs.