This is a: ether type of noise in transistor, and in other semiconductor deviczs. Its intensity is inversely proportional to the freqency. Therefore, it is also called semiconductor noise or 1/f noise. It has been observed that this noise becomes negligible above 1000 Hz. The cause for this noise is not completely understood. It is assumed that it originates in the irregular distribution and flow of carriers on the crystal surface in the vicinity of the depletion region. This noise increases with an increase of d c. voltage between the collector and the base. This noise in a transistor can be minimized by cleaning the crystal surface and by applying a smaller d c. voltage between the collector and base.
This noise is entirely absent in metals. Hence in electronic circuits where flicker noise is to be reduced wire-wound resistors are preferred to carbon resistors.
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