Lecture12

No charge carriers to ow current backward 14 clicker

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Unformatted text preview: filled with electrons.   These appear as “holes” in the Fermi sea of electrons. o  They have an effecLve posiLve charge and can be moved by an E field. o  It is easier to calculate the effect of a field on a small number of holes rather than work with the very large number of electrons filling the band. 12 Semiconductor JuncLons   electrons flow from N region to P region set up E field. o  depleLon region o  allows current in one direcLon Forward voltage: •  depleLon region shrinks •  current flows a`er juncLon voltage overcome Reverse voltage: •  depleLon region grows •  very Lny current 13 Diode   Need to overcome potenLal step to flow current in the posiLve direcLon.  No charge carriers to flow current backward. 14 Clicker: Diode   Why does a diode allow current only in one direcLon? A.  A potenLal is built up that opposes current in the backward direcLon. B.  There are not charge carriers in the conducLon band. C.  Applying a field in the backward direcLon only causes both types of charge carriers to move away from the juncLon. D.  Because it is used as a recLfier. E.  none of the above 15 Transistor   The normal bipolar tr...
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This note was uploaded on 02/24/2014 for the course PHYS 2D taught by Professor Hirsch during the Winter '08 term at UCSD.

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