12 V ±2% regulation with 1 W dissipation ceiling
The 1N4742CPE3/TR8 is a 12 V zener diode in the 1N4742 family from Microchip Technology, rated for 1 W continuous power dissipation in the DO-204AL (DO-41) axial-lead package. The ±2% tolerance on the nominal 12 V zener voltage means the regulation window is 11.76 V to 12.24 V at the test current — tighter than the standard ±5% grade, which matters when the clamped rail feeds a precision reference or an ADC supply.
Operating envelope and dynamic impedance
Maximum zener impedance is 9 Ohms (Zzt at the test current), so the voltage shift under load is bounded — a 10 mA change in zener current shifts the output by less than 90 mV, keeping the rail inside the ±2% tolerance band. Reverse leakage is 5 µA maximum at 9.1 V, which is the knee voltage — below the zener region the diode draws negligible current, so standby power in a shunt regulator or overvoltage clamp stays under 50 µW.
Housed in the DO-204AL (DO-41) axial-lead package, the diode is through-hole mounted — the 0.025-inch diameter leads suit standard 0.040-inch plated-through holes on a 0.100-inch grid. Supplied in Tape & Reel (TR) format, the part is ready for automated insertion or hand assembly from cut tape.