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GATE 2017-2018 :: GATE ECE

  1. The current ib through the base of a silicon npn transistor is 1 + 0.1 cos(10000 π t) mA. At 300 K, the rπ in the small signal model of the transistor is

  2. A.
    250 Ω
    B.
    27.5 Ω
    C.
    25 Ω
    D.
    22.5 Ω

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  3. The power spectral density of a real process X(t) for positive frequencies is shown below. The values of E[X2(t)] and E[X(t)] , respectively, are

  4. A.
    6000/Ï€, 0
    B.
    6400/Ï€, 0
    C.
    6400/Ï€, 20/(Ï€ √2)
    D.
    6000/Ï€, 20/(Ï€ √2)

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  5. In a baseband communications link, frequencies upto 3500 Hz are used for signaling. Using a raised cosine pulse with 75% excess bandwidth and for no inter-symbol interference, the maximum possible signaling rate in symbols per second is
  6. A.
    1750
    B.
    2625
    C.
    4000
    D.
    5250

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  7. The electric field of a uniform plane electromagnetic wave in free space, along the positive x direction, is given by  . The frequency and polarization of the wave, respectively, are
  8. A.
    1.2 GHz and left circular
    B.
    4 Hz and left circular
    C.
    1.2 GHz and right circular
    D.
    4 Hz and right circular

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  9. Consider the given circuit.

    In this circuit, the race around
  10. A.
    does not occur
    B.
    occurs when CLK = 0
    C.
    occurs when CLK = 1 and A = B = 1
    D.
    occurs when CLK = 1 and A = B = 0

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  11. The output Y of a 2-bit comparator is logic 1 whenever the 2-bit input A is greater than the 2-bit input B. The number of combinations for which the output is logic 1, is
  12. A.
    4
    B.
    6
    C.
    8
    D.
    10

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  13. The i-v characteristics of the diode in the circuit given below are

    The current in the circuit is
  14. A.
    10 mA
    B.
    9.3 mA
    C.
    6.67 mA
    D.
    6.2 mA

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  15. In the following figure, C1 and C2 are ideal capacitors. C1 has been charged to 12 V before the ideal switch S is closed at t = 0. The current i(t) for all t is

  16. A.
    zero
    B.
    a step function
    C.
    an exponentially decaying function
    D.
    an impulse function

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  17. The average power delivered to an impedance (4 - j3) Ω by a current 5cos(100π t + 100) A is
  18. A.
    44.2 W
    B.
    50 W
    C.
    62.5 W
    D.
    125 W

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  19. The unilateral Laplace transform of f(t) is 1/(s2 + s + 1). The unilateral Laplace transform of t f (t) is
  20. A.
    - s/(s2 + s + 1)2
    B.
    - (2s + 1)/(s2 + s + 1)2
    C.
    s/(s2 + s + 1)2
    D.
    (2s + 1)/(s2 + s + 1)2

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