75 V zener — bias rail or clamp protection
The 1N6021B is a 75 V zener diode in a DO-35 glass axial-lead package, rated for 500 mW continuous power dissipation. The 75 V nominal breakdown makes it a fit for regulating a high-voltage bias rail — say a 48 V telecom bus stepped up — or for clamping overvoltage transients on a 60 Vdc supply line where the zener conducts at the threshold and shunts the spike to ground.
Parametric fit — tolerance, leakage, impedance
Tolerance is ±5%, so the actual zener voltage for any given unit lands between 71.25 V and 78.75 V. That spread is tight enough to set a consistent clamp threshold across a production run, though a precision reference circuit would call for a ±2% or ±1% grade. Dynamic impedance (Zzt) is 265 Ohms at the zener test current. This is the incremental resistance in the breakdown region; a 265 Ω Zzt means the regulation slope is steeper than a low-voltage zener — a 1 mA change in current shifts the zener voltage by roughly 265 mV. For a bias rail that must stay within a few percent, the series resistor and load variation need to hold the operating current steady.
Temperature range and package — harsh-environment ready
Operating junction temperature spans -65°C to 175°C, which is the full military-grade range. A zener in an engine-bay ECU or a downhole sensor module that sees 150°C ambient still has junction margin. The DO-35 glass body is hermetically sealed — no moisture ingress, no parametric drift from humidity — and the axial leads suit through-hole assembly on a wave-solder line or hand-solder rework.