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ECE :: Exam Questions Paper

  1. In a communication system, a process in which statistical averages and time averages are equal is called as,

  2. A.
    stationary
    B.
    ergodic
    C.
    Gaussian
    D.
    BIBO stable

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  3. The materials not having negative temperature coefficient of resistivity are

  4. A.
    metals
    B.
    semiconductors
    C.
    insulators
    D.
    none of the above

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  5. The input to a binary communication system, denoted by a random variable x, takes on one of the two values 0 or 1 with probabilities and . The behaviour of the communication system is modelled by
    P(Y = 1 |x = 1|) = and P(Y = 0|x = 0) =
    Find P(Y = 1)

  6. A.
    B.
    C.
    1
    D.

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  7. Consider an AM system using a square law detector as shown in figure.

    XC(t) = AC[1 + u x (t)] cos ωct, |ux(t)| << 1
    The signal power at the output is :

  8. A.
    A2Cu2 E[x2(t)]
    B.
    A2Cu2 E(x)
    C.
    D.
    None

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  9. Thermal noise is passed through an ideal low-pass filter having cut-off at fc = ωHz. The auto correlation value of the noise at the output of the filter is given as

  10. A.
    Triangular function over the range
    B.
    Gaussian over the range -∞ ≤ t ≤ ∞
    C.
    A Delta function at t = 0
    D.
    Sin c function over the range - ∞ ≤ t ≤ ∞

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  11. For dielectric to dielectric interface with surface charge density, which of the following statements are true?

    1. Dn2 - Dn1 = rs
    2. Et1 = Et2
    3. En1 = En2

  12. A.
    1, 2 and 3
    B.
    1, 2 and 4
    C.
    1, 2 only
    D.
    1, 4 only

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  13. Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].
    Assertion : FETs are more suitable at the input stages compared to BJTs
    Reason: A FET has lower output impedance than a BJT.

  14. A.
    Both [a] and [r] are true and [r] is the correct reason for [a]
    B.
    Both [a] and [r] are true but [r] is not the correct reason for [a]
    C.
    Both [a] and [r] are false
    D.
    Both [a] and [r] are true

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  15. What are the ultimate purpose of minimizing logic expressions?

    1. To get small size expression.
    2. To reduce the number of variables in the given expression.
    3. To implement the function of the logic expression with least hardware.
    4. To reduce the expression for making it feasible for hardware implementation.
    Select the correct answer from the codes given below:

  16. A.
    1 only
    B.
    2 and 3
    C.
    3 only
    D.
    3 and 4

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  17. A function is given f(t) = sin2t + cos2t. Which of the following is true?

  18. A.
    f has frequency components at 0 and 1/2p Hz
    B.
    f has frequency components at 0 and 1/p Hz
    C.
    f has frequency components at 1/2p and 1/p Hz
    D.
    f has frequency components at 0, l/2p and 1/p Hz

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  19. The amplifier network is shown below:

    re and z0 is:

  20. A.
    6.42 kΩ, 5.6 kΩ
    B.
    6.42 Ω, (5.62) kΩ
    C.
    6.4kΩ, (5.62) kΩ
    D.
    6.42 Ω, 5.6 kΩ

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