2008 MG University B.Tech Electronics& Communication Engineering Examination Question Paper

B.TECH DEGREE EXAMINATION, MAY 2008

Third Semester
SOLID STATE ELECTRONICS (L A S)
( Supplementary, Improvement)

Time: 3 hours Maximum:100 marks

Part A

Answer all questions briefly. Each question carries 4 marks.

1. Sketch the Fermi level in energy band diagram of an intrinsic semiconductor and compare with that of the extrinsic types.
2. Distinguish between direct and indirect band gap semiconductors.
3. Write the Einstein relation and explain.
4. With a neat diagram, explain the Quasi Fermi level.
5. Describe the working of photodiode.
6. What are the advantages and disadvantages of LED?
7. Define how a transistor is biased in active region.
8. Define emitter efficiency and base transport factor and relate them.
9. Explain pinch-off and threshold voltages.
10. Compare n MOS and p MOS.


PART B
Answer either a or b of each module. Each full question carries 12 marks.

MODULE I
11. (a) Derive the expression for the majority and minority carrier concentraions in an n type semiconductor. Obtain the expression for its conductivity.
Or
(b) With the help of neat sketches, explain what is meant by carrier concentration
And Fermi level in intrinsic and extrinsic semiconductors. Derive suitable
Relationship between them.

MODULE 2

12. (a) Sketch the various current componentprofiles in a forward and reverse biased
pn junction diode and explain.
Or
(b) What are the various types of breakdown mechanism that occur when a junction is reverse biased ? Differentiate theim qualitatively Explain their significances.

MODULE 3

13. (a) With the help of neat energy band diagrams explain the working of a tunnel diode. Sketch and explain the VI characteristics, giving its application.
Or
(b) (i)Derive equations for the capacitance of a varactor diode. What is it's application?
(ii)Sketch and explain the forward and reverse VI characteristics of a zener diode.

MODULE 4

14.(a) Sketch the diagram showing all the currentcomponents in a pnp transistor biased in the active region and explain the profiles.

Or
(b) With the help of necessarydiagrams, explain the amplifying and switching actions performed by the BJT in CE configuration. Show the relationship between Ic, Ib and b in both the cases.

MODULE 5

(a) With the help of constructional diagram , describe the working of n-channel JFET. Indicate clearly the ohmic and pinch off regions. Explain the VVR operation and its applications..

Or
(b) With the help of neat constructional diagram and characteristics describe the operation of a depletion typeMOSFET. Sketch the charges induced in the various layers clearly. What are its merits and demerits compared to JFET?