Fixed 9V rail, 1.5 A ceiling — the L7809ABV-DG on the bench
The STMicroelectronics L7809ABV-DG is a fixed 9V positive linear regulator in a TO-220-3 through-hole package, rated for 1.5 A continuous output. It belongs to the L78xx family of three-terminal regulators — the same pinout and footprint as the standard 7809, so it drops into any board originally laid out for a TO-220 9V regulator without rewiring.
The 1.5 A output current is the continuous limit at the rated input-output differential — push beyond that and the thermal shutdown kicks in. PSRR of 61 dB at 120 Hz is the ripple rejection figure for full-wave rectified mains — a 1 V pk-pk ripple on the input is attenuated to roughly 0.9 mV at the output. For a 9 V rail feeding analog circuitry, that keeps the hum out of the signal path. Quiescent current is 6 mA — the regulator's own draw from the input rail regardless of load. In a battery-powered design that sleeps most of the time, that 6 mA is always there, so it matters for standby budget. Operating temperature spans -40°C to 125°C, covering industrial enclosures, outdoor telecom cabinets, and engine-bay-adjacent electronics. The TO-220 tab is the primary heat path — bolt it to a heatsink for sustained loads above a few hundred milliamps.
Protection and compliance
Built-in over-temperature and short-circuit protection mean the regulator survives a dead short on the output or a thermal runaway condition — the die shuts down before the bond wires fuse. No external crowbar or fuse required for basic fault coverage. ROHS3 compliant — no restricted substances above the threshold limits, so it passes EU RoHS and similar regional requirements without an exemption declaration.