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Flicker Noise

Noise related to resistance fluctuation
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Description

The origin of flicker noise is uncertain but arises from resistance fluctuations in a current carrying resistor (or any other electronic component) and the mean squared noise voltage due to 1/f noise and is given by 2 = AR2I2Δf/f, where A is a dimensionless constant (10-11 for carbon), R is the resistance, I the current, Δf the bandwidth of the detector, and f is the frequency to which the detector is tuned.

The value is dependent upon material, design, nature of contacts etc. It is thus possible to modify manufacturing processes to minimize flicker noise.

Foundries have been trying to perfect fabrication techniques such as those related to surface preparation and cleaning that result in higher surface quality and thus lower flicker noise. Design techniques to mitigate flicker noise include chopping, correlated double sampling, switched biasing etc. The switched biasing technique, which effectively cycles a MOS transistor between strong inversion and accumulation, leads to much lower flicker noise in a fashion similar to the recovery phenomenon of the bias-temperature instability (BTI) effect.

The derivative of flicker noise 1/f2 can be observed in the metal interconnects of chips. It has become more evident for very narrow connections where there is a possibility of electromigration due to high current densities. In aluminum, the electromigration begins at current densities of 200 μA/μm2


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