Chapter 5 Lecture - Part 4

Component what happens when the current is turned off

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Unformatted text preview: simply the recombination Note: component. component. – What happens when the current is turned off? • The diode will have a stored charge that doesn’t dissipate The instantaneously Transients and AC Conditions Transients – In the n-type region, excess holes will dissipate In upon recombining with excess electrons in a time dependent manner. dependent – The time dependent hole charge can be described The by: by: Qp(t) = Iτpexp(-t/τp) – Thus charges dissipate exponentially and Thus proportional to the mean lifetime of the charge carrier in the material carrier • See Fig 5-27 Effects of a step turn-off transient in a p+-n diode: (a) current through the diode; (b) decay of stored charge in the n-region; (c) excess hole distribution in the n-region as a function of time during the transient. Transient and AC Conditions Transient • Transient Voltage – Results from this persistent charge after I = 0 – This voltage has a time dependence and behaves This exponentially exponentially – This voltage posses challenges for switching This applications appli...
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