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  • Question

  • Consider the following statements

    1. Impedance of Gunn diode is about tens of ohms.
    2. Impedance of Impatt diode is a few ohms.
    3. Impedance of Impatt diode are of the same order.
    4. Impedance of Impatt diode is more than that of Gunn diode.
    Which of the above statement are correct?


  • Options
  • A. all
  • B. 1 and 2 only
  • C. 1, 2 and 3
  • D. 1, 2 and 4

  • Correct Answer
  • 1 and 2 only 

    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.

    An Impatt diode has n+ - p - i - p + structure and is used with reverse bias.

    It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit.

    The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode.

    The features of Impatt diode oscillator are : Frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%.

    Its applications include police radar systems, low power microwave transmitter etc.

    More questions

    • 1. A copper atom is neutral. Its core has a net charge of

    • Options
    • A. 0
    • B. + 1
    • C. - 1
    • D. + 2
      • Discuss
    • 2. The characteristics of which device has peak point and valley point

    • Options
    • A. SCR
    • B. PUT
    • C. SCS
    • D. Shockley diode
      • Discuss
    • 3. Schrodinger wave equation is partial differential equation.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. The output frequency of a cycloconverter can be changed by changing the firing angle.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. Most of the memory chips in static RAM

    • Options
    • A. do not require any supply
    • B. need 2 V supply
    • C. need 5 V supply
    • D. need 12 V supply
      • Discuss
    • 6. In crystalline solids, atoms are stacked in a regular manner.

    • Options
    • A. True
    • B. False
      • Discuss
    • 7. The classes of solid dielectrics are

    • Options
    • A. A, B, C, D, E, F, H
    • B. A E B F H C D
    • C. Y A E B F H C
    • D. A E B F H C
      • Discuss
    • 8. The unit for mmf is

    • Options
    • A. A
    • B. Wb
    • C. T
    • D. V
      • Discuss
    • 9. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally

    • Options
    • A. equal
    • B. different
    • C. equal or different
    • D. different but sometimes equal
      • Discuss
    • 10. The real part of complex dielectric constant and tan? for a dielectric are 2.1 and 5 x 10-4 at 100 Hz respectively. The imaginary part of dielectric constant at 100 Hz is

    • Options
    • A. 1.05 x 10-3
    • B. 2.1 x 10-3
    • C. 5 x 10-3
    • D. 1.05 x 10-2
      • Discuss

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