noise factor (F) is a dimensionless characteristic value of radio systems, low-noise amplifiers (LNA), active analog circuits, mixer circuits, receiver systems and of operational and differential amplifiers.The noise factor is defined as the ratio of two noise powers at the output of an active quadripole
: The noise power with no input signal, to the amplified noise power resulting from the input noise and present at the output of the quadripole. The noisefactor
(F) and the noise figure (NF) are directly related.
The noise figure is calculated from the tenfold logarithm of the noise factor.