4.3 V Zener with 5 W dissipation
The 1N6635 is a 4.3 V zener diode in the E axial through-hole package, rated for 5 W continuous power dissipation. The ±5% tolerance on the nominal zener voltage means the regulation point sits between 4.085 V and 4.515 V at the test current — tight enough for most clamp and reference circuits in industrial and military-grade supplies. The 500 Ohm maximum zener impedance (Zzt) at the operating point is typical for a 4.3 V device at this power level — the dynamic resistance rises with lower zener voltages, so the regulation accuracy degrades with load current variation. These numbers confirm the diode behaves as a standard zener with a soft knee — the leakage at low reverse bias is negligible for most shunt regulator designs.