Effects of the distributed nature of base resistance on the manifestation of noise in planar transistors

Noise measurements at moderate frequencies on several types of planar bipolar transistors are presented. The results show that the representation of the base region by a single resistance in the equivalent circuit is incompatible with the measured values of thermal noise and base-current noise. A theoretical analysis of thermal and current-induced noise is given for various geometries of base region, and provides a partial explanation of the observed effects.