A transistor amplifier has a measured S/N power of 25 at its input and 8 at its output. Its noise figure in decibels is:
A) 9.10
B) 118
C) 17
D) 4.95

Question

Quizplus · Accepted Answer

The noise figure (NF) of an amplifier is given by NF = (S/N)_input / (S/N)_output. Given S/N_input = 25 and S/N_output = 8, NF = 25/8 = 3.125. The noise figure in decibels is 10 * log10(NF) = 10 * log10(3.125) ≈ 4.95 dB.

A Transistor Amplifier Has a Measured S/N Power of 25