SRM University 2007 B.Tech Information Technology ELECTRONIC DEVICES AND CIRCUITS - Question Paper

39. What is meant by negative resistance region in a UJT?
40. Mention 2 applications of UJT.
41. What is thyristor? Mention a few of them.
42. Draw the symbol of UJT and SCR.
43. Draw the 2 transistor equivalent circuit of a SCR.
44. Define holding current in a SCR.


45. Draw the V-I characteristics of a SCR.
46. State any 2 applications of SCR.
47. Explain why a SCR is operated only in the forward biased condition.
48. Explain how triggering of an SCR can be controlled by the gate signal supplied.
49. DIAC is a bi-directional device. Explain?
50. Draw the volt-ampere characteristics of a TRIAC.
51. Draw the transistor equivalent circuit of a TRIAC.
52. Draw the V-I characteristics of a DIAC.
53. Draw the symbol of DIAC, TRIAC.



TEN MARKS

1. Write short notes on (i) Intrinsic semiconductor
(ii) Extrinsic semiconductor (N kind & P type)
2. With energy hill diagram discuss the operation of PN junction under forward biased and reverse biased condition
3. (a) Write short notes on depletion layer, width of depletion layer.
(b) describe Threshold voltage, Pinch off voltage, valley voltage and Break down
voltage.
4. Explain the construction of PN junction diode and state how will you find the forward and reverse characteristic curve.
5. Explain the terms (i) Avalanche breakdown
(ii) Conductors, semiconductors and insulators.
6. With a neat diagram discuss the construction and operation of a BJT showing all the current components.
7. Sketch the typical input and output characteristics of a common emitter BJT configuration and discuss.


8. Explain the construction and operation of a n-channel junction field effect transistor.
9. (a) Draw the Drain and transfer characteristics of a JFET and discuss.
(b) explain the advantages of JFET over BJT.
10. Explain the operation of UJT relaxation oscillator with a neat diagram.
11. Explain the construction, operation and characteristics of UJT.
12. Discuss in detail with neat sketches the 2 methods of turning on and off the SCR.
13. Sketch the construction of a silicon controlled rectifier. Also, sketch the two-transistor equivalent circuit and show how it is derived from the SCR construction. tag all the terminals and discuss how the device operates.
14. Sketch typical SCR forward and reverse characteristics. Identify all the regions of the characteristics and all important current and voltage levels. discuss the shape of the characteristics in terms of the SCR two-transistor equivalent circuit.

Earning:   Approval pending.