noise factor (F)

The noise factor (F) is a dimensionless characteristic of radio systems, low-noise amplifiers( LNA), active analog circuits, mixing circuits, receiving 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 quadrupole: The noise power without input signal, to the amplified noise power resulting from the input noise and present at the output of the quadripole. Here, the input noise is amplified by the amplifier's gain factor.

The noise factor (F) and the noise figure( NF) are directly related. The noise figure is calculated from the tenfold logarithm of the noise factor.