Zener voltage and thermal budget
The 1N6334US is a 27 V Zener diode rated for 500 mW continuous power dissipation in a hermetic SQ-MELF package. With ±5% tolerance on the 27 V nominal, the regulation window spans 25.65 V to 28.35 V — enough margin for most clamping and shunt-regulator circuits without bin-sorting. The -65°C to +175°C operating range covers the full military temperature grade and then some — useful in avionics or downhole tools where the ambient hits 150°C and the diode still holds its Zzt under 27 ohms.
Leakage and forward drop
Reverse leakage at 21 V is a max of 50 nA — low enough that it won't drift a high-impedance bias network or drain a battery-powered hold-up capacitor. The forward voltage at 1 A is 1.4 V max, so the diode can handle brief forward-surge conditions without cooking the junction.