Current Crowding Effect of Equilateral Polygon Emitter Transistors

This brief deals with current crowding in the equilateral polygon emitter transistor. Simple, analytical expressions are derived for the base current and the base resistance, which can be applied to specific emitter geometries, including the triangular, rectangular, hexagonal, and octagonal emitters. The solution for a device with circular symmetry is obtained when the side number of the polygon approaches infinite. The current crowding effects and the corresponding internal base resistances of different emitter geometries are compared and discussed.