3.3 V zener, 1 W in a MELF
The 1N4728AUR is a 3.3 V zener diode rated for 1 W continuous power dissipation in the DO-213AB MELF package — a common voltage reference or clamping element for low-voltage rails in industrial and telecom designs. With ±5% tolerance on the nominal voltage, the actual zener voltage falls between 3.135 V and 3.465 V, which is tight enough for basic regulation or protection circuits where a precision reference is not required.
Thermal and leakage profile
Reverse leakage is specified at 100 µA max at 1 V reverse bias — well below the zener knee, so the diode draws negligible current until the applied voltage approaches 3.3 V. Maximum forward voltage is 1.2 V at 200 mA, typical for a silicon junction; the diode can be used as a standard rectifier in a pinch, though the 1 W dissipation limit still applies.