Mahatma Gandhi University (MGU) 2007 B.Tech Applied Electronics and Instrumentation - Question Paper

B.Tech Degree Examination, November 2008
Third Semester

Branch: Electronics and Communication, Applied Electronics and Instrumentation, Electronics and Instrumentation

SOLID STATE DEVICES


Time : three Hours Max. : 100 Marks


Part A

ans all ques. briefly.
every ques. carries four marks.


1. discuss how energy bands are formed in a solid.
2. describe and discuss mobility and conductivity.
3. What is meant by carrier lifetime? How does it affect the performance of a device?
4. describe and discuss the diffusion constant with the help of expression.
5. What is varactor diode? How it is formed? What is its use?
6. describe and discuss the static and dynamic resistances of a diode.
7. Differentiate ranging from base transport and emitter efficiency and write the relation ranging from them.
8. What is a schottky transistor? elaborate its advantages?
9. How FET can be used as VVR? elaborate its applications?
10. What is substrate bias effect in MOSFET?

(10×4 = 40 marks)

Part B

ans either A or B part of every ques..
every full ques. carries 12 marks.


11. A. Sketch and discuss the energy band diagrams of (i) intrinsic semiconductor ; (ii) n-type semiconductor ; and (iii) p-type semiconductor at 0 K and 300 K. Show donor/acceptor levels also.

Or

B. What is Hall effect? discuss. define the procedure to measure majority carrier concentrations and mobility of a semiconductor specimen.

12. A. (i) Plot the minority and majority carrier currents as a function of distance across a long abrupt p-n junction. (8 marks)

(ii) Plot the characteristics of a diode and discuss. (4 marks)


B. Derive the expressions for

(a) built-in potential
(b) electric field distribution
(c) potential distribution and,
(d) depletion layer capacitance of a linearly graded p-n junction.

13. A. (i) Derive the expression for the time variation of voltage across a p-n junction as it is switched from forward bias to reverse bias condition.
(6 marks)

(ii) What is meant by storage delay time? How is it related to the current through the diode? (6 marks)

Or

B. (i) Sketch and discuss the characteristics of a photo diode. Write the current voltage relationship. (7 marks)

(ii) discuss the principle of operation of LED. elaborate the materials used for the fabrication of LED? discuss. (5 marks)


14. A. (i) Plot the minority carrier distribution in an npn transistor in its various regions and tag it properly. (6 marks)

(ii) Draw the typical doping profile in a BJT and discuss its significance. (6 marks)

Or

B. (i) What is the difference ranging from transit time and lifetime with respect to the base region of a BJT? Derive expression for transit time. (7 marks)

(ii) define the principle of phototransistor. elaborate its applications?
(5 marks)

15. A. Derive the expression for the drain current of JFET. discuss the approximation made. How the expression is replaced under saturated conditions?

Or

B. Sketch and discuss the energy band diagrams of MOS capacitor under :

(a) Thermal equilibrium (b) Accumulation
(c) Depletion (d) Inversion
(e) Strong inversion.

Earning:   Approval pending.