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Unformatted text preview: ECE 440 Homework 9 Fall 2009 Due: Friday, Nov 13, 2009 1. A voltage V A = 23.03 kT/q is being applied to a step junction diode with n and pside dopings of N A = 10 17 cm3 and N D = 10 16 cm3 . Make a dimensioned log(p and n) versus x sketch of both the majority and minority carrier concentrations in the quasineutral regions of the device. Be sure to identify points of 10 and 20 diffusion lengths on the plot. 2. Consider the p +n step diode pictured above. Note that p is infinite for 0 x x b and p = 0 for x b x x c . Excluding biases that would cause highlevel injection or breakdown, develop an expression for the roomtemperature IV characteristic of the diode. Assume that the depletion width (W) never exceeds x b for all biases of interest. 3. PN junction Simulation. To analyze a pn junction, we solve the continuity equations for electrons and holes, the driftdiffusion equations (which describe how carriers move in response to an electric field), and Poissons equation (because when charge carriers move, they change the...
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 Spring '08
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