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ECE :: Electronic Devices and Circuits

  1. The forbidden band in semiconductors is of the order of

  2. A.
    6 eV
    B.
    1 eV
    C.
    10 eV
    D.
    0.01 eV

  3. For an P-N-P transistor in normal operation its junction are biased as

  4. A.
    emitter base : reverse, collector base : forward
    B.
    emitter base : forward, collector base : reverse
    C.
    emitter base : forward, collector base : forward
    D.
    emitter base : reverse, collector base : reverse

  5. A FET is to be operated as voltage variable resistor. For this drain to source voltage VDS should be,

  6. A.
    74
    B.
    = VP
    C.
    < VP
    D.
    > VP

  7. Assertion (A): FET has characteristics very similar to that of pentode.

    Reason (R): Both FET and pentode are voltage controlled devices.

  8. A.
    Both A and R are true and R is correct explanation of A
    B.
    Both A and R are true but R is not a correct explanation of A
    C.
    A is true but R is false
    D.
    A is false but R is true

  9. The current gain of a bipolar transistor drops at high frequencies because of

  10. A.
    transistor capacitance
    B.
    high current effects in the base
    C.
    parasitic inductive elements
    D.
    the early effect

  11. In an intrinsic semiconductor, the intrinsic charge concentration at any absolute temperature T is proportional to

  12. A.
    T
    B.
    T2
    C.
    T3
    D.
    T4

  13. The conductivity of an intrinsic semiconductor is (symbols have the usual meanings).

  14. A.
    generally less than that a doped semiconductor
    B.
    σi = enin - μp)
    C.
    σi = enin + μp)
    D.
    σi = nin - μp)

  15. The current due to thermionic emission is proportional to

  16. A.
    T
    B.
    T2
    C.
    T3
    D.
    T4

  17. For radiating ultraviolet rays, LEDs use

  18. A.
    zinc sulphide
    B.
    gallium arsenide
    C.
    gallium phosphide
    D.
    none of the above

  19. Addition of a small amount of antimony to germanium will result in

  20. A.
    formation of p-type semiconductor
    B.
    more free electrons than holes in semiconductor
    C.
    antimony concentrating on the edges of the crystal
    D.
    increased resistance