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

The most general case of
1/f
noise in transistors can be described by three independent noise current generators: i
be
between base and emitter, i
bc
between base and collector, and i
ec
between emitter and collector. By short-circuiting the base and the collector to ground and comparing the base and collector noise spectra
S_{IB}(f)
and
S_{IC}(f)
for the case of zero feedback from the emitter with the base and collector noise spectra
S'_{IB}(f)
and
S'_{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 of
S_{IB}(f)
,
S_{IC}(f)
,
S'_{IB}(f)
, and
S'_{IC}(f)
, one can assign physical processes to the current generators i
bc
, i
be
, and i
ec
. It is the aim of this paper to demonstrate theoretically a simple method for locating
1/f
noise sources in BJT's and HBJT's by comparing the base and collector
1/f
noise for the cases without and with strong emitter feedback. In later papers we shall demonstrate experimentally how this method is applied to practical situations.