# Anna University Model Question Paper BE II sem E&I ELECTRON DEVICES

**MODEL PAPER**

**B.E. DEGREE EXAMINATION.**

**Second Semester**

**Electronics and Instrumentation Engineering**

**EI 132 — ELECTRON DEVICES**

(Common to Instrumentation and Control Engineering)

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A — (10 ´ 2 = 20 marks)

- Draw the basic structure of a CRT.
- An electron is injected perpendicularly into a uniform magnetic field of flux density 0.01 Wb/m
^{2}with an initial speed of 10^{7}m/s. What will be the radius of the circular path that the electron describes? - Draw the energy band diagram of
*n*type and*p*type semiconductor. - Compute the value of diffusion length in a single crystal germanium having 100 if the diffusion constant is 47 cm
^{2}/sec. - Mention the important features of power transistor.
- What is Early effect?
- Draw the equivalent circuit and the V–I characteristics of UJT. Mention the important characteristic of the same.
- Draw the high frequency equivalent circuit of FET in common source configuration.
- What is an LCD? Mention its merits and demerits.
- Discuss briefly about the operation of photo diode.

- An electron is injected perpendicularly into a uniform magnetic field of flux density 0.01 Wb/m

PART B — (5 ´ 16 = 80 marks)

- (i) Explain about electrostatic deflection employed in CRT. Derive the necessary expressions. (10)

** **(ii) An electron enters the space between two parallel plates A and B through a small hole in A with an energy of 200 eV at an angle of 60° to A. Calculate the uniform magnetic flux density required to cause the electrons return through another hole set in A at a distance of 0.08 mt from the point of entrance and lying in the same plane as the initial velocity. (6)

- (a) (i) Derive continuity equation. What are its uses? (10)

** ** (ii) The resistivity of intrinsic germanium at 300°K is 0.47 ohm–mt. Calculate the intrinsic density of electrons and holes if the hole and electron mobilities in germanium are 3600 cm^{2}/volt–sec and

1700 cm^{2}/volt–sec. Also calculate the diffusion coefficient for holes and electrons in germanium at 300°K. (6)

Or

** **(b) (i) Explain about Schottky barrier diode. (10)

** ** (ii) The breakdown voltage of the diode is 10 V. Find the value of for the currents and voltage specified. (6)

- (a) (i) A silicon transistor shown in circuit has an . Find the region of operation of transistor. Find the value of for which the transistor comes out of saturation. (10)

** ** (ii) Derive hybrid model of a transistor in common emitter configuration. (6)

Or

** ** (b) Describe the operation of a bipolar junction transistor as a switch. How will you improve its performance if it is to be used for high frequency applications? Suggest a method.

- (a) Draw the volt–ampere characteristic of a JFET and explain about each of the regions of operations of the same with relevant equations.

Or

** **(b) What is a bilateral diode switch? Explain.

- (a) What is a charge transfer device? From the basic principle, explain its operation.

Or

** **(b) With relevant diagrams, describe about the operation of a solar cell.

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