Physics of Devices — DU B.Sc. (Prog.) Physical Science courses pertaining to Electronics Previous Year Question Papers

(b) Explain the transistor as a two-port network and define the four h-parameters used to characterise it. (5) (c) Calculate the electron and hole concentrations for an intrinsic semiconductor given effective density of states Nc = 2.8 X 10[9 cm-3, 3 Nv= 1.04 x 1019 cm-3, band gap Eg = 1.1ev, at 300K. (5) 2. Attempt a total of four questions, including Question (a) Define the effective mass of an electron in a semiconductor. (b) What is the difference between direct and indirect band gap semiconductors? 3. (a) Discuss the basic idea and significance ofcMOS technology in digital electronics. (5) (c) Explain why the Fermi level shifts in doped semiconductors. (b) Explain the construction and working of a Junction Field Effect Transistor (JFET). (5) (d) What is a varactor diode and give one of its application? (c) Explain the effect of temperature on barrier height and contact resistance of metal-semiconductor junctions. (5) (e) Describe the frequency response of a transistor amplifier. 4. (a) Describe the construction and working of a two-stage RC coupled amplifier. (5) (b) Design a relaxation oscillator of 5 kHz frequency using UJT. (5) 2. (a) Explain the characteristics, working principle and applications of the Unijunction Transistor (c) Find the position of the Fermi level in an n-type semiconductor doped with a donor concentration of 1016 cm-3 at 300K. (5) (b) Outline the structure and working of a Metal Oxide Semiconductor Field Effect Transistor (c) Discuss the characteristics and working principle of a tunnel diode. (5) 5. (a) Describe the formation and characteristics of Schottky barrier and Ohmic contact using energy band diagrams. (5)