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ECE :: Electronic Devices and Circuits

  1. Assertion (A): When reverse voltage across a p-n junction is increased, the junction capacitance decreases.

    Reason (R): Capacitance of any layer is inversely proportional to thickness.

  2. 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

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  3. In an n type semiconductor

  4. A.
    number of free electrons and holes are equal
    B.
    number of free electrons is much greater than the number of holes
    C.
    number of free electrons may be equal or less than the number of holes
    D.
    number of holes is greater than the number of free electrons

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  5. Mobility of electrons and holes are equal.

  6. A.
    True
    B.
    False

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  7. Electrons can be emitted from a metal surface due to high electric field.

  8. A.
    True
    B.
    False

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  9. In an n type semiconductor the fermi level is 0.35 eV below the conduction band, the concentration of donor atoms is increased to three times. The new position of Fermi level will be

  10. A.
    0.35 eV below conduction band
    B.
    about 0.32 eV below conduction band
    C.
    about 0.32 eV above conduction band
    D.
    about 0.1 eV below conduction band

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  11. Assertion (A): In a BJT, the base region is very thick.

    Reason (R): In p-n-p transistor most of holes given off by emitter diffuse through the base.

  12. 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

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  13. Assertion (A): The behaviour of FET is similar to that of a pentode.

    Reason (R): FETs and vacuum triode are voltage controlled devices.

  14. 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

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  15. SCR can be turned on by

    1. applying anode voltage at a sufficient fast rate
    2. applying sufficiently large anode voltage
    3. increasing the temperature of SCR to a sufficiently
    4. applying sufficiently large gate current.

  16. A.
    1, 2, 4 only
    B.
    4 only
    C.
    1, 2, 3, 4
    D.
    none

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  17. In a bipolar transistor

  18. A.
    recombination in base regions of both n-p-n and p-n-p transistor is low
    B.
    recombination in base regions of both n-p-n and p-n-p transistors is high
    C.
    recombination in base region of n-p-n transistor is low but that in p-n-p transistor is high
    D.
    recombination in base region of p-n-p transistor is low but that in n-p-n transistor is high

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  19. If for a silicon n-p-n transistor, the base to emitter voltage (VBE) is 0.7 V and the collector to base voltage VCB is 0.2 Volt, then the transistor is operating in the

  20. A.
    normal active mode
    B.
    saturation mode
    C.
    inverse active mode
    D.
    cut off mode

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