Adjustable regulation in a TO-92-3 — what the 100mA ceiling means
The LM317LZ/LFT4 is a 100mA adjustable positive voltage regulator in a TO-92-3 through-hole package — the current ceiling is the first fit check: this is a low-dropout bias supply for op-amp rails, MCU Vref, or sensor front-ends, not a main power rail pass element. Output adjusts from 1.2V up to 37V with two external resistors, and the 40V input maximum gives headroom for unregulated supplies up to 36V nominal.
PSRR and protection — the design-in details
PSRR runs 80dB to 65dB at 120Hz — that 80dB floor at line frequency is relevant when the input comes from a full-wave rectified supply; the rejection drops at higher frequencies, so post-regulation filtering may be needed for switching-noise-sensitive loads. Built-in over-current, over-temperature, and short-circuit protection mean the regulator handles a momentary output short without cascading failure — a practical advantage in breadboard or field-repair scenarios where the load might fault before the supply is sequenced. Quiescent current is 5 mA — not a micropower LDO, but acceptable for always-on bias rails where the load current is in the tens of milliamps and the Iq is a small fraction of the total budget.
Temperature grade and board-level fit
The TO-92-3 package is a three-lead through-hole form factor — it protrudes above the board and is hand-solderable, making it a common choice for rework, prototyping, and low-volume production where SMD reflow is not justified.
Available in Cut Tape and Tape & Box packaging — the Tape & Box option suits automated insertion for through-hole assembly lines, while Cut Tape works for smaller quantities or hand-loading.