47 V Zener, 500 mW, Axial — the board-level clamp
The 1N6340 is a 47 V zener diode in a B, Axial through-hole package, rated for 500 mW continuous power dissipation. Reverse leakage is specified at 50 nA maximum when 36 V is applied across the junction — this is the standby current the zener draws before it enters breakdown, relevant for battery-powered circuits where quiescent draw matters. Maximum zener impedance (Zzt) is 75 Ohms at the nominal 47 V point, which sets the dynamic regulation — the voltage shift per mA of load current through the zener is the product of Zzt and the current change.