B.E. DEGREE EXAMINATION.
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/m2 with an initial speed of 107m/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 cm2/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.
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 cm2/volt–sec and
1700 cm2/volt–sec. Also calculate the diffusion coefficient for holes and electrons in germanium at 300°K. (6)
(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)
(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.
(b) What is a bilateral diode switch? Explain.
- (a) What is a charge transfer device? From the basic principle, explain its operation.
(b) With relevant diagrams, describe about the operation of a solar cell.