I B.Tech - Regular Examinations, June 2009
First Year
BASIC ELECTRONIC DEVICES AND CIRCUITS - SET NO: 1
(Regulation 2007)
Time : 3 hours |
Maximam Marks:80 |
Answer any FIVE Questions
1. (a) With the help of a neat sketch, explain the principle of working of a CRT.
(b) In a CRT, the length of deflecting plates is 2cm. The spacing between the
plates is 0.6cm. The distance of the screen from the center of the plates is
16cm. Calculate the deflection sensitivity in m/volt if the final anode voltage
is:
i. 600V and
ii. 900V.
2.(a) How does the reverse sturation current of diode varies with temperature. Ex-
plain.
(b) Draw the energy band diagram of p-n diode for no bias, forward bias and
reverse bias and explain.
3.(a) A 15-0-15 Volts (rms) ideal transformer is used with a full wave rectifier circuit
with diodes having forward drop of 1 volt. The load is a resistance of 100ohm
and a capacitor of 10,000µf is used as a filter across the load resistance. Cal-
culate the dc load current and voltage.
(b) Draw the circuit diagram of a bridge rectifier circuit with L-section filter and
explain its operation.
4. (a) Draw the circuit for BJT in C.C. configuration and draw the input and output
characteristics.
(b) Explain the terms α, β, ICEO,ICBO,β* and γ pertaining to BJT.
5. (a) Determine the stability factor for the circuit shown in figure 5a.
(b) Calculate the thermal resistance for the 2N338 transistor for which the manu-
facturer specifies Pc,max=125mW at 250C free-air temperature and maximum
junction temperature Tj=1500C. What is the junction temperature if the col-
lector dissipation is 75mW?
6. (a) Explain the method of evaluating h parameters for a transistor in CB config-
uration.
(b) A CC amplifier is driven by a voltage source of internal resistance Rs=1k
.
The load impedance if RL=1K
. The transistor parameters are hic= 1.1K
,
hfc = -51, hrc=1, hoc= 25µA/V. Compute input and output impedance of the
amplifier.
7.(a) Define Desensitivity D. What is the significance of this?
(b) An amplifier without feedback gives a fundamental output of 36V with 7
percent second-harmonic distortion when the input is 0.028V. If 1.2 percent
of the output is fed back into the input in a negative voltage series feedback
circuit, what is the output voltage? If the fundamental output is maintained
at 36V but the second-harmonic distortion is reduced to 1 percent, what is
the input voltage?
8. (a) Consider the two section RC network shown in figure 8a. Find the Vi/Vf ’
function, and verify that it is not possible to obtain 1800phase shift with a
finite attenuation.
(b) State the similarities and differences between series and parallel resonance
crystal oscillator circuits.
|