# Identify the Maximum Voltage that can be applied across Zener, MOSFET and Transistor

#### Electronic_Maniac

Joined Oct 26, 2017
253
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?

#### crutschow

Joined Mar 14, 2008
24,969
1. How to find the maximum voltage that can be applied across zener?
You do not apply a voltage directly across a Zener, you apply a current (often from a voltage through a resistor).
If you apply a voltage above the Zener voltage with nothing to limit the current, then the current rapidly becomes very large and will likely zap the Zener.

So it's the maximum current that's of concern and that's the maximum power dissipation divided by the Zener voltage.
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?
Yes.

• Electronic_Maniac