Noise figure and Noise factor :

The noise factor (f) of an amplifier or any network is defined in terms of the signal to noise ratio at the i/p and o/p of the system. It is defined as:

$F = \frac{S/N at i/p}{S/N at o/p} $

$= \frac{Psi}{Pni} \times \frac{Pno}{Pso}$ …