5.1 V regulation in a hermetic MELF
The 1N4733AUR is a 5.1 V zener diode in a DO-213AB MELF package, rated for 1 W continuous power dissipation. The ±5% tolerance on the nominal voltage means the actual zener voltage falls between 4.845 V and 5.355 V at the test current — tight enough for most 5 V rail clamping or reference applications without bin-sorting. The DO-213AB MELF package is a hermetic glass body with metallized end caps — it handles thermal cycling and moisture better than plastic SMD packages.
Maximum zener impedance (Zzt) is 7 Ohms at the test current. This impedance sets the voltage regulation accuracy under varying current: a 10 mA change in zener current shifts the output voltage by up to 70 mV. For a precision 5 V reference, the bias current must stay stable — a current source or high-value resistor feeding the zener keeps the operating point on the flat part of the I-V curve. Reverse leakage current is 10 µA maximum at 1 V reverse voltage — that is well below the zener knee, so this spec matters for circuits where the zener sits across a signal line and must not load it until the threshold is reached. Forward voltage is 1.2 V maximum at 200 mA, typical for a silicon junction of this die size.
The base product number is 1N4733 — the 'A' suffix denotes ±5% tolerance (versus ±10% for the non-suffix variant), and the 'UR' suffix indicates the DO-213AB MELF package. When ordering, confirm the full suffix matches your BOM line to avoid receiving a different package variant.