I've been trying to determine the parameters of the hybrid-pi model for a given bjt transistor. Some books give the following as the model:
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Is it just me or are the rb and rpi resistances impossible to calculate by manipulating the circuit only from the B, C, E terminals? It seems to me that the system of the equations we can write is under-determined. If we omit rb (as is mostly done) though, it becomes very simple to solve.
Is rb determined via some other way?