of an Insulator
is the minimum voltage that causes a portion of an insulator to become electrically conductive
of a diode
is the minimum reverse
voltage to make the diode conduct in reverse. Some devices (such as TRIACs
) also have a forward breakdown voltage
Breakdown voltage is a characteristic of an insulator
that defines the maximum voltage
difference that can be applied across the material before the insulator collapses and conducts. In solid insulating materials, this usually creates a weakened path within the material by creating permanent molecular or physical changes by the sudden current
. Within rarefied gases found in certain types of lamps, breakdown voltage
is also sometimes called the "striking voltage".
Two different breakdown voltage measurements of a material are the AC and impulse breakdown voltages. The AC voltage is the line frequency of the mains (either 50 or 60 Hz depending on where you live). The impulse breakdown voltage is simulating lightning strikes, and usually uses a 1.2 microsecond rise for the wave to reach 90% amplitude then drops back down to 50% amplitude after 50 microseconds.
Two technical standards governing performing these tests are ASTM D1816 and ASTM D3300 published by ASTM.
Breakdown in vacuum
In standard conditions at atmospheric pressure, gas serves as an excellent insulator, requiring the application of a significant voltage before breaking down (e.g. lightning). In vacuum, this breakdown potential may decrease to an extent that two uninsulated surfaces with different potentials might induce the electrical breakdown of the surrounding gas. This has some useful applications in industry (e.g. the production of microprocessors) but in other situations may damage an apparatus, as breakdown is analogous to a short circuit.
The breakdown voltage in vacuum is represented as
is the breakdown potential in volts DC
that depend on the surrounding gas,
represents the pressure of the surrounding gas,
represents the distance in centimetres
between the electrodes, and
represents the Secondary Electron Emission Coefficient
Breakdown voltage is a parameter
of a diode
that defines the largest reverse voltage
that can be applied without causing an exponential increase in the current
in the diode. As long as the current is limited, exceeding the breakdown voltage of a diode does no harm to the diode. In fact, Zener diodes
are essentially just heavily doped
normal diodes that exploit the breakdown voltage of a diode to provide regulation of voltage levels.