In many Zener Diode datasheets, I have witnessed that in the Absolute Maximum Ratings section, they don't include the "Maximum Voltage" that can be applied to the Zener diode. If the applied voltage crosses the Zener breakdown voltage, then the voltage will start to conduct and will enter in the Reverse Breakdown Region.

The datasheet only include maximum power dissipation, Thermal, temperature and Maximum Forward voltage information.

I want to understand why the maximum voltage rating is not provided in the zener diode datasheet.

My questions:

  1. How to find the maximum voltage that can be applied across zener? Should I reverse calculate the Maximum Zener Voltage from the Maximum Power Dissipation rating provided in the datasheet? If so, could you provide an example.

  2. And in case of a transistor/MOSFET, the maximum voltage that can be applied across it, would be the Maximum Collector-Emitter / Drain-Source Voltage, right?

Please help to provide clarity

Edit :

Zener Datasheet = Zener

Transistor Datasheet = Transistor


  • \$\begingroup\$ Please provide a data sheet link. \$\endgroup\$ – Andy aka Apr 26 '20 at 8:02
  • \$\begingroup\$ Provided the datasheets of the components. \$\endgroup\$ – Newbie Apr 26 '20 at 8:06

Zeners are designed to operate in breakdown. Thus hotspots must be avoided.

MOSFETS and Bipolars are not designed to operating in breakdown, tho I've seen schematics using the 2N2169 NPN (Jim Williams of LTC uses this device) in a sub-nanosecond pulse generator, where the avalanche performance (a breakdown mode) produces the fast onset of charge movement and hence the fast edge.

I suspect your performance with such a circuit will strongly depend on who manufactured the transistor, given the avalanche speed is not spec'd in datasheets.


The rated Zener breakdown voltage IS the maximum voltage that can or should be applied. If you try to apply more voltage, the current will increase (theoretically) without limit, exceed the device's power rating and destroy it. The maximum current can be calculated by the Zener voltage and the maximum power rating by P = IV, or I = P/V.

A Zener diode id typically powered through a resistor or a constant-current source, and maintains its rated voltage across it, and thus is commonly used for voltage regulation.

A bipolar transistor and mosfet have three terminals, and thus have several ratings for the maximum voltages between the different terminals.

  • \$\begingroup\$ From what I understand, If the Zener Breakdown Voltage is 36V, and its Zener Maximum Power Dissipation is 300mW, the maximum current that can flow through the device during the zener breakdown condition is 8.3mA? \$\endgroup\$ – Newbie Apr 26 '20 at 7:35

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