5.1 V shunt regulation with 1 W dissipation ceiling
The 1N4733AP/TR12 is a 5.1 V Zener diode from Microchip Technology's 1N4733 family, rated for 1 W maximum power dissipation in the standard DO-204AL (DO-41) axial-lead package. The ±5% tolerance on the nominal Zener voltage means the regulation window spans 4.845 V to 5.355 V — tight enough for most 5 V rail clamping or reference applications without requiring a precision-grade part.
The 1 W power rating sets the maximum steady-state dissipation: at 5.1 V, the diode can conduct up to about 196 mA before exceeding the thermal limit at 25°C ambient. The 7 Ohm max Zzt impedance at the Zener test current means the regulation voltage shifts roughly 70 mV per 10 mA of bias current change — a consideration for circuits where the load current varies widely. Reverse leakage is specified at 10 µA maximum at 1 V reverse bias — well below the Zener knee, confirming the diode is fully off below the regulation voltage. The forward voltage drop of 1.2 V at 200 mA is a standard silicon junction characteristic — the diode conducts in the forward direction like a conventional rectifier when the anode is positive, which matters for circuits that use the Zener in a bidirectional clamping configuration.