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Prévia do material em texto

Step 1 of 3 3.010E The current flowing through the junction of a semiconductor is, I Where J, is the current density of holes, is the current density of electrons, A is the area of the junction, D, is the diffusion constant of holes, is the diffusion constant of electrons, L, is the diffusion length of holes, is the diffusion length of electrons, is the terminal voltage, and are the carrier concentration levels. Step 2 of 3 Substitute for and for where n, is the carrier concentration in the intrinsic silicon, is the acceptor dopant concentration and ND is the donor dopant concentration. I = + = = When a negative voltage, V (reverse biased) is applied with a magnitude of a few times then the exponential term would essentially be zero, and the current across the junction becomes negative and constant. Step 3 of 3 Therefore, the term + can be substituted with the term Iₛ The relation for the current Iₛ is, It is given that the acceptor dopant concentration is very much greater than the donor dopant concentration, The term D. would yield a very low value when compared with the term D D, because the as the L,ND denominator (consisting of NA) value increases, the term decreases. So neglect the term then the equation is, = Therefore, the saturation current is,