10 V Zener — the voltage reference for a 500 mW thermal budget
Microchip Technology 1N6000B/TR is a 10 V Zener diode in the standard DO-35 axial-lead glass package, rated for 500 mW continuous power dissipation. The ±5% tolerance on the nominal Zener voltage means this part holds the regulation point between 9.5 V and 10.5 V at the specified test current — tight enough for a bias rail or a reference shunt in a discrete supply. A 15 Ohm maximum Zener impedance (Zzt) means the dynamic resistance is low enough that a 10 mA change in load current shifts the regulated voltage by only 150 mV worst-case. This matters when the Zener doubles as a voltage reference feeding an ADC's external reference pin or a comparator's threshold divider.
DO-35 glass package — hermetic seal for the full temperature range
The DO-204AH (DO-35) axial-lead glass package is a hermetic, double-plug construction rated for continuous operation from -65°C to 175°C. This temperature range covers military avionics bay ambient, engine-mounted sensors, and down-hole tool environments where the diode sees both thermal cycling and humidity exposure that would crack a plastic SMD package. Through-hole mounting with axial leads means the diode body is bonded into the glass envelope, not overmolded. The lead-to-glass seal is a matched-expansion alloy that survives thermal shock from -65°C to 175°C without leaking. For a board that must pass MIL-STD-883 Method 1014 gross-leak testing, this package is the baseline.
Reverse leakage and forward drop — the two secondary checks
Reverse leakage is specified at 100 nA maximum when the applied voltage is 8 V (80% of the nominal Zener voltage). This confirms the Zener knee is sharp: below the breakdown region the diode draws negligible current, so it does not load down the bias supply it is meant to regulate.