ELECTRONICS PREVIOUS OBJECTIVE QUESTIONS AND SOLUTIONS

  1. The p-n junction diode is a

Ans: unilateral device

 2. A semiconductor has —– temperature coefficient of resistance.

Ans: negative

 3. A metal has ——– temperature coefficient of resistance.

Ans: positive

4.  A JFET has

Ans: two built in diode

 5.  The value of intrinsic stand-off ratio of UJT should be

                   Ans: <1

 6.  The output impedance in an ideal op-amp is

                Ans: zero

7. Match the following

Part A                                      Part B

  1. LED                                   1. Heavily doped
  2. APD                                  2. Coherent radiation
  3. Tunnel diode                     3. Spontaneous emission
  4. Laser                                 4. Current gain

Ans:  a- 3, b- 4, c-1, d-2

8. Following are the process steps to fabricate an IC

    1. Crystal growth
    2. Epitaxial growth
    3. Photo etching
    4. Diffusion
    5. Vacuum evaporation of aluminium

The correct sequence of fabrication is

Ans: 1,2,3,4,5

 9. Match the lists:

List1                                         List 2

(band gap in eV)                    (materials)

  1. 0.67                                      1. Ga As
  2. 1.1                                        2. Cadmium sulphate
  3. 1.4                                        3. Si
  4. 2.4                                        4. Ge

Ans: a-4, b-3,c-1,d-2

 10. Match the lists:

List 1                                          list 2

  1. Gamma rays                       1. 400-700nm
  2. Visible light                         2. 1-10cm
  3. Radio waves                        3. 3*10^3 m
  4. Microwaves                        4. 4*10^-11 m

Ans: a-4, b-1, c-3, d-2

11.  Semiconductor are sensitive to

    1. Heat
    2. Magnetic field
    3. Light energy
    4. All of the above

Ans: d

12. Photo diode is reverse biased because

         Ans: reverse current is small as compared to photo    current

13. Avalanche photodiodes are preferred over PIN diodes in optical communication systems because of

               Ans: larger power handling capacity

14. In UJT, the stand-off ratio is

               Ans: 0.7

14. Tunnel diode is basically a junction diode with

             Ans: high doping in p and n regions, both

15. An op-amp behaves like an ideal amplifier decreases, the bandwidth

              Ans: 5 KHz

16.If the gain of an ideal amplifier decreases, the bandwidth

             Ans: increases

17. To use as a memory, which is more stable?

            Ans: bistable multivibrator

18. The time base of CRO is controlled by

             Ans: saw tooth waveform

19. Photo diode is reverse biased because

         Ans: reverse current is small as compared to photo current

20. In SCR’s snubber circuits employ

             Ans: A combination of R and C

 21. Step down regulator produces an output

            Ans: low voltage at high current

 22. Negative feedback in amplifier results in

    1. Reduced voltage gain
    2. Reduced sensitivity
    3. Decreased bandwidth
    4. Reduced distortion

Of these statements:

Ans: 1,2,4 are correct

23. Consider the following statements:

    1. Figure of merit and CMRR are the same parameters.
    2. In an op-amp CMRR is very high approaching to infinity
    3. The input stage of an op-amp is usually a differential amplifier

Ans: 2 and 3 are correct

 24. Semiconductor materials are made up of

      Ans: covalent bond

 25. A UJT has

       Ans: negative resistance characteristics

 26. CMRR for a differential amplifier should be

             Ans: large

 27. The current in a zener diode is controlled by

            Ans: external circuit’s resistance

 28. The ripple factor of a half wave rectifier is found to be

            Ans: 1.21

 29. Hartley oscillator is commonly used in

            Ans: radio receiver

 30. An ideal op-amp has

                Ans: infinite differential gain and zero common mode gain

 31. SCR turns off conducting state to blocking state on

               Ans: reducing anode current below holding current value

 32. A balanced modulator essentially is

            Ans: a product modulator

 33. Photo conductive devices are made of

           Ans: semiconductor materials

34. The figure of merit of logic family is given by

             Ans: (propagation delay time)* (power dissipation)

 35. The leakage current in silicon p-n junction at room temperature is of the order of

Ans: µ µA

 36. The most suitable instrument for the measurement of voltage is

              Ans: CRO

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