Bipolar Transistor
In section multiple equations we already came across
a model for the bipolar transistor.
Here we extend that model with some additional physical effects:
emitter current crowding, collector epi-layer resistance and weak avalanche multiplication.
For that purpose two auxiliary variables are introduced:
vnc the voltage over the collector epi-layer,
vrb the voltage over the base resistance.
The model describes both the forward and reverse region of the BJT behavior. So when the measurement data only covers the forward region, as the data given below, all the reverse parameters need to be fixed.