Thyristors UJT and Optoelectronic Devices: Important Part B Questions

Electron Devices

Chapter 6: Thyristors UJT and Optoelectronic Devices

Important Part B Questions

1. Explain the construction and working of Shockley diode.

2. Draw and explain the characteristics of Shockley diode stating its applications.

3. Explain the construction of SCR.

4. Enumerate the structure of a SCR, with a two transistor model derive an expression for anode current (I_A) Also indicate its V‒I characteristics.

5. Explain the working principle of SCR and its V‒I characteristics.

6. Draw and explain the operation of SCR using two transistor equivalent circuit.

7. Derive the expression for the anode current from the two transistor model of SCR.

8. Draw and explain the characteristics of SCR.

9. Define the following with respect to SCR:

i. Forward breakover voltage ii. Holding current iii. Latching current iv. Reverse breakdown voltage.

10. State the various specifications of SCR.

11. State the merits of SCR.

12. State the demerits of SCR.

13. State the various applications of SCR.

14. Explain the operation, characteristics and applications of SCR.

15. Explain the basic construction of a diac.

16. Explain the working principle of diac.

17. Explain the four transistor analogy for a diac.

18. Draw and explain the characteristics of diac. Explain its operation.

19. Explain the working and characteristics of DIAC and its applications.

20. What is triac? Explain its construction, symbol and equivalent circuit.

21. Explain the working of triac.

22. Draw and explain the V‒I characteristics of triac. Explain its operation.

23. List the applications of triac.

24. Explain any one application of triac in detail.

25. Compare SCR and triac.

26. List the merits of triac.

27. List the demerits of triac.

28. Draw the basic structure of TRIAC and its symbol.

29. Explain the basic construction and working of UJT. Draw its equivalent circuit.

30. Explain the equivalent circuit and define intrinsic stand off ratio of UJT.

31. Draw and explain the characteristics of UJT.

32. Define negative resistance region and valley point current with respect to UJT.

33. Sketch the UJT emitter characteristics for I_B2 = 0, V_BB = 20 V and V_BB = 5 V. Identify each region and important points on the characteristics.

34. Explain how a UJT functions as relaxation oscillator.

35. Describe the construction, operation and characteristics of UJT.

36. Enumerate the construction and operation of LED.

37. Explain the working principle of LED.

38. State the materials used in LED.

39. Explain the output characteristics of LED.

40. State the advantages of LED.

41. State the applications of LED.

42. State the disadvantages of LED.

43. Compare LED with P‒N junction diode.

44. What is seven segment display? How numbers are displayed using seven segment display?

45. Write a note on seven segment display.

46. Explain construction and operation of LCD.

47. State the types of liquid crystals and explain their structures in brief.

48. Explain the construction and working principle of dynamic scattering LCD.

49. Explain the construction and working principle of field effect LCD.

50. State the advantages of LCD.

51. State the disadvantages of LCD.

52. Compare LED and LCD.

53. An indicator requires voltage to be displayed in seven segment format. However, the power requirement for the display should be very low. Choose a proper display device and justify your choice. Also indicate the characteristics and operating principle of such a display device.

54. Explain the construction and working principle of a phototransistor.

55. Draw and explain the characteristics of phototransistor.

56. State the applications of phototransistor and discuss any one in detail.

57. Write a note on phototransistor.

58. Explain the construction and working of optocoupler.

59. Write a note on optocoupler.

60. Write a note on LED - phototransistor optocoupler.

61. State the characteristics of optocoupler.

62. State the advantages of optocoupler.

63. State the applications of optocouplers.

64. Explain the construction, symbol and characteristics of photovoltaic cell.

65. List the applications of photovoltaic cell.

66. Write a note on solar cell.

67. State the features of power MOSFET.

68. Draw and explain the DMOS structure.

69. Draw and explain the VMOS structure.

70. Draw and explain the characteristics of power MOSFET.

71. Write a note on safe operating area of power MOSFET.

72. Write a short note on power MOSFET.

73. What is the name implies VMOS?