The design of silicon power transistors to minimize the effects of thermal feedback

The effects of thermal feedback on the characteristics of multiple emitter stripe silicon power transistors are considered in detail and 1) a method is presented for correlating the isothermal characteristics with the effects of thermal feedback so that observed output characteristics may be predicted and 2) emitter stripe designs are developed to achieve uniform temperature and power distributions. A number of authors have considered the effects of nonuniform temperature distribution. This paper will present a method of isothermal characterization of collector current and base-emitter voltage as functions of power density and temperature, which when combined with two-dimensional thermal analysis for proposed designs, allows the prediction of steady-state device characteristics. The specific temperature uniformity required to alleviate thermal feedback can be predicted and achieved by optimizing the thermal coupling between emitter stripes.