I B.Tech - Regular Examinations, June 2009
First Year
BASIC ELECTRONIC DEVICES AND CIRCUITS - SET NO: 3
(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) Derive the expression for contact difference of potential V0 in the case of an
open circuited p-n junction.
(b) What is the ratio of current for a forward bias of 0.08 V to the current for the
same magnitude of reverse bias for the Germanium diode.
3.(a) Discuss the operation of HW recitifier with and without capacitor filter.
(b) Draw the Half wave rectifier circuit using a step down Transformer with Vs
= 46 sin(100p t) and a semiconductor diode. Calculate the turns ratio of
the Transformer windings when the primary voltage of the Transformer is 230
volts.
4. (a) Derive the relation between a and ß of the BJT.
(b) Derive the relation between ICEO and ICBO of a transistor.
(c) Explain how transistor can be used as an amplifier.
5. (a) What do you understand by dc and ac load line? Explain how to choose the
operating point?
(b) For a fixed bias configuration, determine IbQ, ICQ and VceQ using the following
specifications: Vcc= 16V, ß =90, Rc = 2.7K
, Rb=470K
and also find the
saturation current Isat.
6. Find the overall h parameters of the composite transistor shown in figure 6
7.(a) List the steps required to carry out the analysis of a feedback amplifier.
(b) Calculate voltage gain, input impedance and output impedance of a CE am-
plifier with voltage-shunt negative feedback.
8.(a) Find Vi/Vf ’ for the network shown in figure 8a
Sketch the circuit of a phase shift oscillator using feedback network shown in
figure 8b.
(c) Find the expression for the frequency of oscillation, assuming that the network
does not load down the amplifier of question (b).
(d) Find the minimum gain required for oscillations of the circuit of question (b).
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