The 1N4744APE3/TR12 is a 15 V zener diode from Microchip Technology, rated for 1 W continuous power dissipation in a DO-204AL (DO-41) axial-lead package. The ±5% tolerance band means the actual zener voltage at 25 °C falls between 14.25 V and 15.75 V — tight enough for most 15 V shunt regulation or voltage-clamping tasks where a precision reference is not required. Maximum zener impedance is 14 Ohms (Zzt at the test current). This impedance governs how much the zener voltage shifts with current — a 10 mA change in zener current shifts the output by roughly 140 mV. For a shunt regulator feeding a constant load, that is within the ±5% tolerance; for a variable load, the dynamic impedance adds to the regulation error budget.
Temperature range and reverse leakage — the operating envelope
Reverse leakage is specified at 5 µA maximum when 11.4 V is applied across the junction — this is the leakage at 76 % of the nominal zener voltage, well below the breakdown knee, so the diode draws negligible current in the off state. Forward voltage drop is 1.2 V maximum at 200 mA forward current. If the part is used in a bidirectional clamping circuit or as a rectifier, this forward drop adds to the conduction loss budget.
Active production — sourcing for the BOM line
The tape-and-reel packaging (TR suffix) indicates it is supplied on a reel for automated pick-and-place assembly, though the DO-41 axial body is typically hand-inserted or formed for through-hole insertion — the reel format suits high-volume board assembly houses that handle axial components.