The noise caused by random variations in the arrival of electrons or holes at the output electrode of an amplifying device

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ISRO VSSC Technical Assistant Electronics 2018 Official Paper

Answer 1

Shot noise:

It is a type of noise that appears in all amplifying & active devices.
It is associated with a current flow
The noise caused by random variations in the arrival of electrons or holes at the output electrode of an amplifying device is called shot noise.
In semiconductor devices, shot Noise is due to the random variation in the diffusion of minority carriers
Current is a flow of carriers each of which carriers a finite amount of charge.
For diodes, the exact expression for RMS shot noise \(I_n^2 = 2\;{I_{dC}}qB\)

26 June 1

At low frequencies, the noise varies approximately as 1/f, and is called an excess, or flicker noise. It is caused by the recombination and generation of carriers on the surface of the crystal.
In intermediate frequencies, the noise is independent of frequency. This white noise is caused by the bulk resistance of the semiconductor material and the statistical variation of the currents (shot noise).
The third region is characterized by an increase of the noise figure with frequency and is essentially caused by a decrease in power gain with frequency.