The noise figure of an amplifier is the difference in dB of the SNR on the input and the SNR on the output of the amplifier. SNR is the ratio of signal power to noise power. NF and noise power do not depend on impedance, but noise voltage RMS does depend on temperature and impedance.

Noise figure NF:	dB
Input impedance z:	Ω
Working temperature T:	°C   °F   °K

Used formulae:

(1.)	1. NF = 10*log(SNR_in)-10*log(SNR_out) = 10*log((P_n_in+P_n_amp)/P_n_in)

(2.)	2. P_n_amp / P_n_in = 10\(NF * 0.1) - 1