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Home ‣ Electronics and Communication Engineering ‣ Microwave Communication See What Others Are Saying!
  • Question

  • Assertion (A): The phenomenon of differential mobility is called transferred electron effect.

    Reason (R): GaAs exhibits transferred electron effect.


  • Options
  • A. Both A and R are correct and R is correct explanation of A
  • B. Both A and R are correct but R is not correct explanation of A
  • C. A is correct but R is wrong
  • D. A is wrong but R is correct

  • Correct Answer
  • Both A and R are correct but R is not correct explanation of A 

    Explanation
    A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field.

    This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms.

    A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.

    Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.

    More questions

    • 1. As compared to dimensions of most feeds, the skin depth at microwave frequencies is

    • Options
    • A. of the same magnitude
    • B. much larger
    • C. much smaller
    • D. either (b) or (c)
      • Discuss
    • 2. For a 1 cm x 2 cm air filled rectangular waveguide the maximum frequency should be less than about

    • Options
    • A. 1000 MHz
    • B. 5000 MHz
    • C. 14000 MHz
    • D. 140000 MHz
      • Discuss
    • 3. In a radio receiver

    • Options
    • A. all stages contribute equally to noise
    • B. RF stage has no effect on S/N ratio
    • C. mixer stage contributes most of the noise generated
      • Discuss
    • 4. As compared to an ordinary semiconductor diode, a Schottky diode

    • Options
    • A. has higher reverse saturation current
    • B. has higher reverse saturation current and higher cut in voltage
    • C. has higher reverse saturation current and lower cut in voltage
    • D. has lower reverse saturation current and lower cut in voltage
      • Discuss
    • 5. A 3 port circulator is in the given figure. Its scattering matrix is

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 6. The total field developed by an antenna array at a distant point is

    • Options
    • A. phasor sum of fields produced by individual antennas of the array
    • B. algebraic sum of fields produced by individual antennas of the array
    • C. either (a) or (b) depending on type of array
    • D. neither (a) nor (b)
      • Discuss
    • 7. A standard cell of 1.0185 V is used with a slide wire potentiometer. The balance was obtained at 60 cm. When an unknown emf was connected, the balance was obtained at 82 cm. The magnitude of unknown emf is

    • Options
    • A. 1.39 V
    • B. 0.75 V
    • C. 13.9 V
    • D. 7.45 V
      • Discuss
    • 8. The number of valence electrons in donor impurity are

    • Options
    • A. 5
    • B. 4
    • C. 3
    • D. 1
      • Discuss
    • 9. Assertion (A): A DIAC has four layers but only two terminals.

      Reason (R): A DIAC can conduct in both directions.


    • Options
    • A. Both A and R are correct and R is correct explanation of A
    • B. Both A and R correct but R is not correct explanation of A
    • C. A is correct but R is wrong
    • D. A is wrong but R is correct
      • Discuss
    • 10. A NAND gate has 3 inputs and one output. The number of thyristors required for this gate are

    • Options
    • A. 1
    • B. 2
    • C. 3
    • D. 3 or 4
      • Discuss

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