5V fixed linear regulator in a TO-92-3 — what it does and where it fits
The Texas Instruments LM78L05ACZ/LFT3 is a fixed-output positive linear regulator delivering 5 V at up to 100 mA in a through-hole TO-92-3 package.
Key ratings and what they mean for the BOM
The fixed 5 V output eliminates the need for external resistor dividers — just input and output caps, and the rail is set. At 100 mA output, this part is sized for low-current loads: a small MCU, a few op-amps, or an isolated sensor supply. Exceed that and the regulator drops out of regulation or hits thermal shutdown. The 62 dB PSRR at 120 Hz tells you how well the part rejects ripple from a full-wave rectified mains supply — useful when the input comes from a transformer-and-capacitor front end rather than a switching preregulator. Quiescent current sits at 3 mA, which is modest for a linear regulator but worth noting in battery-powered designs where every millamp counts. Over-temperature and short-circuit protection are built in, so the part survives a momentary output short without damage.
Temperature grade and environment
Rated for 0°C to 125°C operating junction temperature, this part covers commercial and most industrial indoor environments.
Lifecycle and sourcing posture
That means no last-time-buy pressure and no forced redesign for a replacement. ROHS3 compliant, so it clears the RoHS directive without exemption paperwork. For a BOM freeze, this part is a stable line item; no PCN watch needed unless the fab moves.