Question

If a matched attenuator with a loss of 3.2 dB is placed between the source and the amplifier’s input, what is the operating spot noise figure of the attenuator amplifier cascade if the attenuator’s physical temperature is 290 K?

(a) 9 db

(b) 11.3 db

(c) 10.4 db

(d) 13.3 db

This question was posed to me during an interview.

Question is from Noise topic in division EDC Overview of Electronic Devices & Circuits

Answer 1

Right answer is (d) 13.3 db

Best explanation: Here Te is 290[(20.89-1) + (2.089)(7.98-1)] or 4544.4K. Hence the required answer is 1 + 4544.4/290 = 212 or 13.3 db.