I B.Tech - Regular Examinations, June 2009
First Year
BASIC ELECTRONIC DEVICES AND CIRCUITS - SET NO: 2
(Regulation 2007)
Time : 3 hours |
Maximam Marks:80 |
Answer any FIVE Questions
1. (a) Draw the schematic diagram of a CRT and explain about the various sections
and the materials used.
(b) In a CRT, the electrons emitted are accelerated by a potential of 500V. The
length of the deflecting plates is 1.3 cm. Distance between the deflecting plates
is 0.5 cm. The distance between the centre of the deflecting plates and the
screen is 20 cm. Determine the value of electrostatic deflection sensitivity.
2.(a) Draw and explain the V-I characteristics of a p-n junction diode. Use equations
wherever necessary.
(b) The transition capacitance of an abrupt junction diode is 30pf at 8V. Deter-
mine the value of capacitance for an increase in the bias voltage of 2V.
3.(a) Explain the circuit diagram of a single phase full-wave bridge rectifier and
sketch the input and output wave forms.
(b) Define percentage regulation and prove that the regulation of both half wave
and full wave rectifier is given by percentage regulation equal to Rf/
Rl
× 100%.
4. (a) Draw the circuit and explain the characteristics of BJT (input and output
characteristics) in C.E. configuration
(b) Give the specifications, parameters and typical values of a silicon NPN tran-
sistor.
5. (a) What is the necessity to stabilize the operating point of transistor amplifier?
(b) What is thermal runaway?
(c) What is thermal runaway?(c) For a fixed bias configuration determine I c, R c, R b and Vce using the following
specifications: V cc=12V, V c=6V, ß =80, I b = 40 µA.
6. Show that the exact expression for hfe in terms of the CB hybrid parameters is from this formula obtain the approximate expression for hfe.
7.(a) An amplifier has a gain of -100 and a distortion of 8%. What is the effect of
introducing negative feedback with feedback factor of 0.05?
(b) Find Af for a CE stage with an un bypassed emitter resistor.
8. (a) What is condition of unity loop gain to sustain oscillations? Prove it.
(b) Prove that the ratio of the parallel to series resonant frequencies of a crystal
is 1+1/2(C/C’).
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