Improved modeling of output conductance and cut-off frequency of bipolar transistors

The collector epilayer is a crucial element in the behaviour of modern bipolar transistors. Compact models for its description, like the Kull model, are also therefore of crucial importance. We give a Mextram-based improvement to these models for quasi-saturation, and show that the output conductance and the cut-off frequency are much smoother. Apart from ohmic quasi-saturation, we also include velocity saturation, which also leads to quasi-saturation (Kirk effect).