NOISE CHARACTERIZATION OF POLYSILICON EMITTER BIPOLAR TRANSISTORS

Abstract

A biasing circuit is designed and implemented for the measurement of noise from the base and the collector of an npn bipolar transistor. This circuit is able to measure the coherence between the base noise current and the collector noise current with the help of HP3562A Dynamic Signal Analyzer's built-in Coherence function. The coherence and noise measurement were cartied out on an npn polysilicon emitter bipolar transistors. The measurements were carried out on two classes of devices, one having an interfacial oxide layer at the interface and the other without having an oxide layer at the interface. The coherence measurements on these devices revealed that the oxide layer at the interface plays an important role in the noise characteristics of these devices. It was concluded by careful observation of the results that the coherence is not only a function bias, but also a function of oxide thickness. Base and collector noise current were measured at different biasing conditions. It was concluded that both follow the same relationship i.e., Iab2 ? Ib2 and IBC2 ? IC2 for various types for devices.