ABSTRACT
This chapter describes the Spice model of the bipolar transistor uses similar or identical equations. It shows the parameters of the bipolar transistor model and its relation to the parameters. The temperature dependence of the transistor model is described based on the model of the SPICE program. It also discusses the deviations from the actual temperature dependence. All parameters of the transistor model are temperature dependent. Some parameters are very strong functions of temperature. To simplify the model description, the temperature dependence of some parameters is often neglected. Although the SPICE bipolar transistor model uses more than 40 parameters, many features of the bipolar transistor are not included in the model. The performance of the Si bipolar transistor can be greatly enhanced with proper engineering of the base bandgap profile using a narrower bandgap material, SiGe, an alloy of Si and Ge. Structure wise, a SiGe HBT is essentially a Si BJT with a SiGe base.
