Location of 1/f noise sources in BJT's and HBJT's—I. theory

The most general case of1/fnoise in transistors can be described by three independent noise current generators: ibebetween base and emitter, ibcbetween base and collector, and iecbetween emitter and collector. By short-circuiting the base and the collector to ground and comparing the base and collector noise spectraSIB(f)andSIC(f)for the case of zero feedback from the emitter with the base and collector noise spectraS'IB(f)andS'IC(f)for the case of strong feedback from the emitter, one can evaluate the relative strength of the three noise sources. By measuring the current dependence ofSIB(f),SIC(f),S'IB(f), andS'IC(f), one can assign physical processes to the current generators ibc, ibe, and iec. It is the aim of this paper to demonstrate theoretically a simple method for locating1/fnoise sources in BJT's and HBJT's by comparing the base and collector1/fnoise for the cases without and with strong emitter feedback. In later papers we shall demonstrate experimentally how this method is applied to practical situations.