What this -12V regulator does
The L7912CP is a fixed -12V output linear regulator from STMicroelectronics, delivering up to 1.5A continuous current. It's the negative-rail counterpart to the 78xx series — you feed it a negative unregulated input down to -35V max, and it holds -12V within its dropout budget. The 1.1V typical dropout at 1A means the input must be at least -13.1V to maintain regulation at full load. Below that, the output starts to sag — factor that into your transformer secondary and rectifier drop calculations.
PSRR and protection features
PSRR is 60 dB at 120 Hz — that's the ripple rejection on the negative rail. For an audio preamp or analog front end running off a bipolar supply, this keeps 120 Hz hum from the rectifier out of the signal path. It's not a high-frequency LDO; the rejection rolls off above a few kHz, so pair it with a post-filter if your load draws fast transients. On-chip protection includes over-temperature shutdown and output short-circuit current limiting. The thermal limit kicks in around 150°C junction — the TO-220FP tab needs a heatsink if you're pulling more than a few hundred mA continuously in a warm enclosure.
Through-hole TO-220-3 Full Pack — the tab is fully moulded plastic, no exposed metal pad. That means the thermal path goes through the plastic to the ambient, not to a heatsink tab you can solder to a copper plane. For rework, it's a straightforward three-lead part: heat all three pins simultaneously with a wide tip or hot-air nozzle, lift the part, then wick the holes clean. No risk of lifting pads like a QFN; the leads are thick and the holes are plated through. Fine for bench supplies, industrial control panels, and audio gear. Not rated for under-hood or outdoor telecom without environmental screening.
It's a standard catalogue part, not a custom or discontinued line.