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Breakdown Voltage (Insulator) = The minimum voltage that causes a portion of an insulator to become electrically conductive.

Breakdown Voltage (diode) = 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 weakenned path within the material by creating permanent molecular or physical changes by the sudden flow of current. Within rarified 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.

Is a parameter of a diode that defines the largest reverse voltage potential 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.

• Electrical breakdown
• Avalanche breakdown
• Avalanche diode
• Zener diode

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