GTU Last Year question papers

GUJARAT TECHNOLOGICAL UNIVERSITY

B.E. Sem-III Examination December 2009

Subject code: 131101

Subject Name: Basic Electronics

Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

Q.1 (a) Define following terms:

(i) Electron Volt (eV).

(ii) Mobility of charge carries.

(iii) Barrier potential.

(iv) Voltage equivalent of temperature.

(b) Explain energy band diagram of insulator, semiconductor and conductor.

(c) Explain following for npn transistor.

(i) Current components.

(ii) Regions of operation according to biasing condition

Q.2 (a) Draw the circuit diagram of full wave bridge rectifier and give its input and output waveforms. Also derive the expression for the d.c. current.

(b) Explain Hall effect. Derive expression of Hall voltage and state its applications.

OR

(b) A bar of n type silicon has length of 5 cm and circular cross sectional area of 10 mm2. When it is subjected to a voltage of 1 V along its length, the current flowing through it is 5 mA. Calculate the concentration of free electrons and drift velocity of electrons. Assume mobility of free electrons to be 1300 cm2/V-s.

Q.3 (a) Compare zener and avalanche break down.

(b) What is transition capacitance in p-n junction diode? Give its physical significance.

(c) State the use of clipping circuits. Discuss with neat sketch working of a biased parallel clipper.

OR

Q.3 (a) Explain principle of operation of a Photodiode.

(b) Discuss piece-wise linear model of a diode.

(c) Compare V-I characteristics of Silicon and Germanium p-n junction diode.

Q.4 (a) Draw CE transistor configuration and give its input and output characteristics. Also derive the relation between current gain of CE, CB and CC configurations.

(b) Give constructional details of JFET and give its characteristics. Why FET is called voltage controlled device?

OR

Q.4 (a) Explain the operation of Emitter follower amplifier. Why is it named as emitter follower?

(b) Give points of difference between BJT and FET. Also explain FET as voltage variable resistor.

Q.5 (a) State the need of biasing. Discuss voltage divider bias circuit and mention its advantages.

(b) What is the difference between voltage amplifier and power amplifier? State important features of power amplifier and classify them based on the position of Q point.

OR

Q.5 (a) Discuss h-parameter equivalent circuit for transistor in CE configuration.

(b) State the role of voltage regulators in power supplies? Discuss working of a series voltage regulator.