GTU previous years question papers
GUJARAT TECHNOLOGICAL UNIVERSITY
BE SEM-III Examination-Dec.-2011
Subject code: 131101
Subject Name: Basic Electronics
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Explain the concept of potential energy barrier. 07
(b) State the limitations of Rutherford model and explain Bohr atomic model.
Q.2 (a) Explain the mobility and conductivity using electron-gas theory. Also derive the expression of current density.
(b) Describe the Hall effect and also explain how it is help to determine the different properties of semiconducting material.
(b) Explain the generation of holes and electrons in an intrinsic semiconductor.
Q.3 (a) Explain the formation of barrier potential in open circuited PN junction diode. Also derive the expression for barrier potential.
(b) A diode having internal resistance 20Ω is used for half-wave
rectification. If the applied voltage V=50sin(ωt) and load resistance
1) Im, Idc, Irms
2) d.c. output voltage
3) efficiency of rectification.
Q.3 (a) Define the rectification and describe the full wave bridge rectifier with the help of neat circuit diagram and waveforms.
(b) The resistivities of two sides of a step graded germanium diode are 2
4.cm and 1 4.cm for p-side and n-side respectively. Calculate the height of potential energy barrier Vo. Assume μp=1800 cm2/v.sec,
μn=2100 cm2/v.sec, q=1.6×10-19 ni= 2.5 ×1013 per cm3
Q.4 (a) Define following terms:
2) voltage equivalent of temperature
3) electric potential
4) electron volt
5) Ripple factor
6) base spreading resistance
7) pinch off voltage
(b) Explain the different types of clipping circuits. 07
Q.4 (a) Explain the output characteristic of n-p-n transistor in CE
configuration. Also indicate different regions.
(b) Determine h-parameters for the two port network. Also draw the hybrid model for CE, CB and CC configurations.
Q.5 (a) Explain DC load line and Q-point for any transistor configuration. Also state the necessity of biasing and list biasing methods for transistor.
(b) List the basic configurations of a low frequency FET amplifier. Explain any one of them with the help of neat circuit diagram and small signal equivalent circuit.
Q.5 (a) Classify the power amplifiers based on the position of Q-point on the ac load line. Also explain Class-B push-pull amplifier.
(b) Explain the principle of operation of JFET. Also compare FET with BJT.