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Analog Electronics - Engineering

Q1:

The signal input to a given amplifier is made up of 100 mΩ signal power and 1 mΩ noise power. The amplifier contributes an additional 100 mΩ of noise and has a power gain of 20 dB. The noise factor is

A 1

B 1.5

C 2.0

D 15

ANS:C - 2.0

Input SNR = 100 mW/1mW = 100.

Power gain = 20 dB = 100.

Output signal power = 100 mW*100.

Output Noise power = 1 mW*100+100 = 200mW.

Output SNR = (100*100)/200 = 50.

Noise Factor = (Input SNR)/(Output SNR) = 100/50 = 2.