Noise factor for a system is defined as the ratio of

Q9. Noise factor for a system is defined as the ratio of

Options:

a) Input noise power (P_no) to output noise power (P_ni)
b) output noise power (P_no) to input noise power (P_ni)
c) output noise power (P_no) to input signal power (P_si)
d) output signal power (P_so) to input noise power (P_ni)

Correct Answer: b) output noise power (P_no) to input noise power (P_ni)

Explanation :

The noise factor of a system is defined as the ratio of output noise power (P_no) to input noise power (P_ni):
F_n = P_no/ P_ni, at standard room temperature 290K
= P_no/GKBT₀


The input noise power is P_ni= GKBT₀,
G is the gain of the amplifier
K= 1.38 X 10^-23 J/°K , Boltzmann's constant
B is the bandwidth of the network in hertz (Hz)
To = 290°K
Noise factor may also be defined as the ratio of Signal to Noise ratio at the output to Signal to Noise ratio at the input.
i.e., F_n = S_ni/ S_no