Experimental results on low frequency noise in quasiself-aligned bipolarn-p-njunction transistors, with widely varying emitter/base junction dimensions are presented and compared with former results obtained on devices of the same type. The power spectral density of base current fluctuations was found to depend linearly on the inverse of the area of the emitter/base interface junction, implying localization of the low frequency noise sources on the interface, rather than on the transistor perimeter. An application of current-to-voltage converters for studies of current fluctuations is also discussed and compared with a more conventional technique. ©1997 American Institute of Physics.