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ECE :: Exam Questions Paper

  1. For the BJT shown in figure, β = 50, the value of VCE is:

  2. A.
    3.13 V
    B.
    4.24 V
    C.
    5.18 V
    D.
    none

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  3. An average response rectifier type electronic voltameter has a d.c. voltage of 10 V applied to it. What is the meter reading?

  4. A.
    7.1 V
    B.
    10 V
    C.
    11.1 V
    D.
    22.2 V

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  5. Consider the common emitter amplifier shown below with the following circuit parameters: β = 100, gm = 0.3861 A/V, r0 = ∞ rp = 259 Ω, Rs = 1 kΩ, RB = 93 kΩ, RC = 250 Ω, RL = 1 kW, C1 = ∞ and C2 = 4.7mF.

    The lower cut-off frequency due to C2 is

  6. A.
    33.9 Hz
    B.
    27.1 Hz
    C.
    13.6 Hz
    D.
    16.9 Hz

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  7. Number of fundamental cut-sets of any graph will be

  8. A.
    same as the number of twigs
    B.
    same as the number of tree branches
    C.
    same as the number of nodes
    D.
    equal to one

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  9. Consider a silicon p-n junction at room temperature having the following parameters:
    Doping on the n-side = 1 x 1017 cm-3
    Depletion width on the n-side = 0.1 μm
    Depletion width on the p-side = 1.0 μm
    Intrinsic carrier concentration = 1.4 x 1014F. cm-1.
    Thermal voltage = 26mV
    Permittivity of free space = 8.85 x 10-14F. cm-1.
    Dielectric constant of silicon = 12. A built in potential of the junction.

  10. A.
    is 0.70V
    B.
    is 0.76V
    C.
    is 0.82V
    D.
    cannot be estimated from the data given

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  11. A message signal x(t) is amplitude modulated with carrier c(t).
    x(t) = 2 sin 600pt
    c(t) = 8 cos (2p x 106 t)
    such that the modulated signal is
    (8 + 2 sin 600pt) [cos 2p x 106 t]
    The total side band power is:

  12. A.
    B.
    C.
    D.
    0.5ω

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  13. The cross section of a JFET is shown in the following figure. Let Va be - 2 V and let Vp be the initial pinch-off voltage. If the width W is doubled (with other geometrical parameters and doping levels remaining the same), then the ratio between the mutual transconductances of the initial and the modified JFET is

  14. A.
    4
    B.
    C.
    D.

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  15. Simplify : A + B + A B + (A + B)AB + C(B + AB)

  16. A.
    B + A
    B.
    C
    C.
    C
    D.
    1

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  17. Which one of the following driving point functions does not represent an LC network?

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  19. A 2 μF capacitor is shunted by a 1 kΩ maintained at temperature 400 K. The rms noise voltage across the capacitor over the entire frequency band is:

  20. A.
    6.25 x 10-8 V
    B.
    5.25 x 10-6 V
    C.
    6.25 x 10-6 V
    D.
    5.25 x 10-8 V

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