A number of students have had trouble getting their DC bias conditions working in the lab. This is because the Beta of our lab transistors may not match the PSpice model. I would compare the Beta’s I measured in Lab 7 with what my PSpice output file is telling me in order to gauge the potential accuracy of the PSpice results. My advice is to adjust the base biasing resistors with a potentiometer to get the correct collector current. Then replace the pot with a standard value resistor. If you need to increase the collector current, then you either need to increase RB2 or decrease RB1 – and vice versa if you need to decrease the collector current. One of the reasons that you may be getting non-optimal DC conditions is that in the PSpice we are using the 2N2222 model and I think in your lab kit you have the 2N4401 transistor. From some quick simulations, it appears that the 2N4401 Beta is roughly half of the 2N2222.
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This note was uploaded on 01/01/2012 for the course ECEN 325 taught by Professor Silva during the Spring '08 term at Texas A&M.