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ECE :: Electronic Devices and Circuits

  1. A varactor diode is used for

  2. A.
    tuning
    B.
    rectification
    C.
    amplification
    D.
    rectification and amplification

  3. One eV = 1.602 x 10-19 joules.

  4. A.
    True
    B.
    False

  5. Assertion (A): When VDS is more than rated value the drain current in a JFET is very high.

    Reason (R): When VDS is more than rated value, avalanche breakdown occurs.

  6. 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

  7. If ib is plate current, eb is plate voltage and ec is grid voltage the v-i curve of a vacuum triode is
    ib = 0.003 (eb + kec)n. Typical values of k and n are

  8. A.
    0.5 and 1
    B.
    - 2 and 1
    C.
    30 and 1
    D.
    30 and 1.5

  9. In which material do conduction and valence bands overlap

  10. A.
    insulators
    B.
    conductors
    C.
    both conductor and semiconductor
    D.
    semiconductors

  11. For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in illumination results in

  12. A.
    a change in O.C. voltage
    B.
    a change in S.C. current
    C.
    a decrease in resistance
    D.
    an increase in resistance

  13. Discrete transistors T1 and T2 having maximum collector current rating of 0.75 amp are connected in parallel as shown in the figure, this combination is treated as a single transistor to carry a total current of 1 ampere, when biased with self bias circuit. When the circuit is switched on, T1 draws 0.55 amps and T2 draws 0.45 amps. If the supply is kept on continuously, ultimately it is very likely that

  14. A.
    Both T1, and T2 get damaged
    B.
    Both T1, and T2 will be safe.
    C.
    T1 Will get damaged and T2 will be safe
    D.
    T2 will get damaged and T1, will be safe.

  15. Assertion (A): A high junction temperature may destroy a diode.

    Reason (R): As temperature increases the reverse saturation current increases.

  16. 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

  17. When a diode is not conducting, its bias is

  18. A.
    forward
    B.
    zero
    C.
    reverse
    D.
    zero or reverse

  19. The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply of frequency of

  20. A.
    30 kHz
    B.
    15 kHz
    C.
    5 kHz
    D.
    20 kHz