22. It spectrum density of thermal noise at room temperature is 4 x 10-21 W/Hz, then available noise power for a bandwidth of 1 MHz is ___ watt.
A. 4 x 10-27
B. 4 x 10-21
C. 4 x 10-15
D. 4 x 10-9

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23. Ceramic filters
A. are used for single-sideband generation
B. use magnetostrictive materials in their construction
C. use a lattice configuration just like crystal filters
D. are similar in construction to mechanical filters

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24. The value of thermal noise voltage for a resistor of 4 K for a bandwidth of 1 MHz and 'spectrum density of 4 x 10-21 W/Hz is
A.0.8
B.8
C.0.64
D.80

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25. Indicate the noise whose source is in a category different from that of the other three.
A. solar noise
B. cosmic noise
C. atmospheric noise
D. galactic noise

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26. Ten telecommunication links working in tandem each have an S/N ratio of 60 dB. Their overall S/N ratio is ___ dB.
A.20
B. (60)1/2
C.50
D.60

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27. Noise figure is used as figure-of-merit of
A. oscillator
B. amplifier
C. modulator
D. isolator

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28. Indicate which one of the following types of noise does NOT occur in transistors
A. shot noise
B. flicker noise
C. partition noise
D. resistance noise

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