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Hybrid-pi model parameter determination

S

sert

Jan 1, 1970
0
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:

http://i33.tinypic.com/2m2xvtt.png

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?
 
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