PSpice Application Notes

PSpice App Note_Modeling Schottky Diodes

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APPLICATION NOTE 1 Introduction This document explains how the model parameters IS and N can be modified to set the forward voltage drop of a Schottky diode. Attached test case shows the simulation results of varying these parameters. The project has three simulation profiles; 1. dc: DC sweep analysis of forward biased schottky diode as shown in Fig. 2. 2. IS_Variation: Nested DC sweep. Shows effect of IS variation. 3. N_Variation: Nested DC sweep. Shows effect of N variation. Schottky Diode Schottky diode, also known as hot carrier diode is a semiconductor diode with low forward voltage and a very fast switching action. Unlike a PN-junction diode, a Schottky Diode has a metal–semiconductor (M–S) junction in which a metal comes in close contact with a semiconductor material. Schottky diodes do not have a recovery time, as there is nothing to recover from (i.e. no charge carrier depletion region at the junction). The switching time is ~100 ps for the small signal diodes, and up to tens of nanoseconds for special high-capacity power diodes. (1) (2) Where Developing Model With respect to the above diode equation, we can see that the forward voltage drop, V, depends on the current, I, but only weakly. V increases by 60 millivolts for each factor of 10 that I increases. Alternatively, V increases by 60 millivolts for each factor of 10 that IS decreases. So, the forward voltage drop for your circuit's bias conditions can be set by changing IS parameter. You can change this in the diode's .MODEL statement. For Schottky diodes, values of IS are larger when compared to diffusion diodes of the same area. The model parameter N can also be used to adjust the forward voltage drop, but changing N will make the I-V curve deviate from the normal slope of a decade per 60 millivolts. We do not recommend changing N

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