How to find out the breakdown voltage?

A diode typically has a high resistance in the reverse direction and does not allow electrons to flow in this reverse-biased mode. When the reverse voltage reaches a certain value, this resistance drops and the diode conducts in reverse-biased mode. The potential at which this occurs is called the breakdown voltage. The threshold voltage at which this occurs is known as the breakdown voltage or dielectric strength. In a gas, the breakdown voltage is determined by Paschen’s Law.

Paschen’s Law is an equation that gives the breakdown voltage as a function of atmospheric pressure and gap length.

Vb = Bpd/[ln(Apd) − ln[ln(1 + 1/γse)]]

Vb is the DC breakdown voltage

p is the pressure of the gas,

d is the gap distance in meters

A and B are constants that depend on the surrounding gas

γse is the secondary electron emission coefficient.

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