Topic: Analog Electronics
Gain and NF of a single stage amplifier is 10 dB and 3 dB respectively. When two such amplifiers cascaded then gain and NF of cascaded amplifier will be:
- A. Gain : 20 dB, NF : 3.2 dB
- B. Gain : 20 dB, NF : 6.0 dB
- C. Gain : 13 dB, NF : 3.6 dB
- D. Gain : 13 dB, NF : 6.7 dB
Answer: A. Gain : 20 dB, NF : 3.2 dB
Explanation: G1 = G2 = 10 dB = 10, F1 = F2 = 3 dB = 2. Overall noise figure = F1 + (F2 - 1)/G1 = 2 + 1/10 = 2.1. Noise figure (dB) = 10 log10 2.1 = 3.2 dB. Overall gain (dB) = G1(dB) + G2(dB) = 20 dB.