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An amplifier has three stages for which Te1 = 150 K (first stage), Te3 = 350 K, and Te3 = 600 K (output stage). Available power gain of the first stage is 10 and overall input effective noise temperature is 190 K
Que: What is the cascade's operating spot noise figure when used with a source of noise temperature Ts = 50 K
  • a)
    1.34 dB
  • b)
    3.96 dB
  • c)
    6.81 dB
  • d)
    None of the above.
Correct answer is option 'C'. Can you explain this answer?
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An amplifier has three stages for which Te1= 150 K (first stage), Te3=...
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An amplifier has three stages for which Te1= 150 K (first stage), Te3=...
Given parameters:
- Te1 = 150 K
- Te2 = 350 K
- Te3 = 600 K
- Power gain of first stage = 10
- Overall input effective noise temperature = 190 K
- Source noise temperature = 50 K

Calculating the cascaded noise figure:
1. Calculate the noise factor of each stage using the available power gain and the stage's effective noise temperature:
- NF1 = (Te1/To) * (1 + 1/G1) - 1 = (150/290) * (1 + 1/10) - 1 = 2.1
- NF2 = (Te2/To) * (1 + 1/G2) - 1 = (350/290) * (1 + 1/1) - 1 = 2.2
- NF3 = (Te3/To) * (1 + 1/G3) - 1 = (600/290) * (1 + 1/1) - 1 = 3.1
where To is the reference temperature of 290 K and G1, G2, and G3 are the power gains of the respective stages.

2. Calculate the overall noise factor of the cascaded amplifier:
- NFcasc = NF1 + (NF2 - 1)/G1 + (NF3 - 1)/(G1*G2) = 2.1 + (2.2 - 1)/10 + (3.1 - 1)/(10*1) = 2.3

3. Calculate the cascaded noise figure:
- NF = 10*log10(NFcasc) = 10*log10(2.3) = 6.81 dB

Therefore, the cascaded operating spot noise figure is 6.81 dB when used with a source of noise temperature 50 K. The correct answer is option C.
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An amplifier has three stages for which Te1= 150 K (first stage), Te3=350 K, and Te3=600 K (output stage). Available power gain of the first stage is 10 and overall input effective noise temperature is 190 KQue: What is the cascade's operating spot noise figure when used with a source of noise temperature Ts = 50 Ka)1.34 dBb)3.96 dBc)6.81 dBd)None of the above.Correct answer is option 'C'. Can you explain this answer?
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An amplifier has three stages for which Te1= 150 K (first stage), Te3=350 K, and Te3=600 K (output stage). Available power gain of the first stage is 10 and overall input effective noise temperature is 190 KQue: What is the cascade's operating spot noise figure when used with a source of noise temperature Ts = 50 Ka)1.34 dBb)3.96 dBc)6.81 dBd)None of the above.Correct answer is option 'C'. Can you explain this answer? for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Question and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus. Information about An amplifier has three stages for which Te1= 150 K (first stage), Te3=350 K, and Te3=600 K (output stage). Available power gain of the first stage is 10 and overall input effective noise temperature is 190 KQue: What is the cascade's operating spot noise figure when used with a source of noise temperature Ts = 50 Ka)1.34 dBb)3.96 dBc)6.81 dBd)None of the above.Correct answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An amplifier has three stages for which Te1= 150 K (first stage), Te3=350 K, and Te3=600 K (output stage). Available power gain of the first stage is 10 and overall input effective noise temperature is 190 KQue: What is the cascade's operating spot noise figure when used with a source of noise temperature Ts = 50 Ka)1.34 dBb)3.96 dBc)6.81 dBd)None of the above.Correct answer is option 'C'. Can you explain this answer?.
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