Experience with the new compact MEXTRAM model for bipolar transistors

The improved performance of the compact bipolar transistor model MEXTRAM is demonstrated by comparison with Gummel-Poon (GP) model calculations and measured DC and high-frequency data. The MEXTRAM model contains extended modeling of the collector epilayer and the inactive region of the base-collector epilayer and the parasitic pnp. It has five internal nodes, whereas the GP model has three. The advantage is a more accurate prediction of the DC behavior and the f_t fall-off at high currents. The AC small-signal behavior at frequencies ⩾f_t is dominated by the inactive part of the device. If unphysical fit parameters are accepted, the GP model can obtain in the forward mode up to the top of the f_t nearly as good a fit as MEXTRAM does; the predictive capability, especially for down-scaled devices, however, will remain inferior. This is a very important point for circuit optimization MEXTRAM has been used successfully in this area, e.g. for ECL gates