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| [[File:Square1.jpg|thumb|High voltage dielectric breakdown within a block of [[Poly(methyl methacrylate)|plexiglas]]]]
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| The '''breakdown voltage''' of an [[Insulator (electrical)|insulator]] is the minimum voltage that causes a portion of an insulator to become electrically [[Conductor (material)|conductive]].
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| The '''breakdown voltage''' of a [[diode]] is the minimum ''reverse'' voltage to make the diode conduct in reverse. Some devices (such as [[TRIAC]]s) also have a ''forward breakdown voltage''.
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| ==Solids==
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| Breakdown voltage is a characteristic of an [[Electrical insulation|insulator]] that defines the maximum [[Breakdown potential|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 [[electric current|current]]. Within rarefied gases found in certain types of lamps, '''breakdown voltage''' is also sometimes called the "striking voltage".<ref>J. M. Meek and J. D. Craggs, Electrical Breakdown of Gases,
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| John Wiley & Sons, Chichester, 1978.</ref>
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| The breakdown voltage of a material is not a definite value because it is a form of failure and there is a statistical probability whether the material will fail at a given voltage. When a value is given it is usually the mean breakdown voltage of a large sample. Another term is also [[Dielectric withstand test|withstand voltage]] where the probability of failure at a given voltage is so low it is considered, when designing insulation, that the material will not fail at this voltage.
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| Two different breakdown voltage measurements of a material are the AC and impulse breakdown voltages. The AC voltage is the [[utility frequency|line frequency of the mains]]. 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.<ref>Emelyanov, A.A., Izv. Vyssh. Uchebn. Zaved., Fiz., 1989, no. 4, p. 103.</ref>
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| Two technical standards governing performing these tests are ASTM D1816 and ASTM D3300 published by ASTM.<ref>Kalyatskii, I.I., Kassirov, G.M., and Smirnov, G.V., Prib. Tekh. Eksp., 1974, no. 4, p. 84.</ref>
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| ==Gases and vacuum==
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| {{main|Gas discharge}}
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| 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 partial 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.<ref>Stefanov, L.S., Tekhnika vysokikh napryazhenii (High-Voltage Engineering), Leningrad: Energiya, 1967.</ref>
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| In a gas, the breakdown voltage can be determined by [[Paschen's Law]].
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| The breakdown voltage in a partial vacuum is represented as<ref>G. Cuttone, C. Marchetta, L. Torrisi, G. Della Mea, A. Quaranta,
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| V. Rigato and S. Zandolin, ''Surface Treatment of HV
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| Electrodes for Superconducting Cyclotron Beam Extraction,''
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| IEEE. Trans. DEI, Vol. 4, pp. 218<223, 1997.</ref><ref>H. Moscicka-Grzesiak, H. Gruszka and M. Stroinski, ‘‘Influence
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| of Electrode Curvature on Predischarge Phenomena and Electric
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| Strength at 50 Hz of a Vacuum</ref>
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| :<ref>R. V. Latham, High Voltage Vacuum Insulation: Basic concepts
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| and technological practice, Academic Press, London, 1995.</ref>
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| <math>
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| V_\mathrm{b} = \frac {Bpd}{\ln Apd - \ln(\ln(1 + \frac {1}{\gamma_\mathrm{se} }))}
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| </math>
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| where <math>V_\mathrm{b}</math> is the breakdown potential in volts [[Direct current|DC]], <math>A</math> and <math>B</math> are [[Constant (mathematics)|constant]]s that depend on the surrounding gas, <math>p</math> represents the pressure of the surrounding gas, <math> d </math> represents the distance in centimetres between the electrodes, and <math> \gamma_\mathrm{se} </math> represents the [[Secondary emission|Secondary Electron Emission]] Coefficient.
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| A detailed derivation and some background information is given in the article about [[Paschen's law]].
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| ==Diodes and other semiconductors==
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| [[File:Diode-IV-Curve.svg|thumb|Diode I-V diagram]]
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| 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 [[electrical current|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 diode]]s are essentially just [[Doping (semiconductor)|heavily doped]] normal diodes that exploit the breakdown voltage of a diode to provide regulation of voltage levels.
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| ==References==
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| {{reflist}}
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| ==See also==
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| *[[Dielectric strength]]
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| *[[Electrical breakdown]]
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| *[[Avalanche breakdown]]
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| *[[Avalanche diode]]
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| [[Category:Electrical breakdown]]
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| [[Category:Electrical parameters]]
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| [[pl:Napięcie przebicia]]
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