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Code No: R21026
R10
SET - 1
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRONIC DEVICES AND CIRCUITS
(Com. to EEE, ECE, EIE, ECC, CSE, IT, BME)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) Explain the construction and working principle of CRT.
b) With the help of a block schematic, explain the working of a CRO.
(8M+7M)
2.
a) Distinguish between drift and diffusion current in a semiconductor. State continuity
equation.
b) Derive an expression for current density in an N-type semiconductor in terms of drift
velocity. Show that the conductivity is given by σ = neµn.
(8M+7M)
3.
a) Compare the characteristics of a P-N junction diode, Zener diode and tunnel diode.
b) Explain Zener diode as a voltage regulator in detail.
(7M+8M)
4.
a) Discuss about the principle of operation of bridge rectifier circuit. Mention the advantages
and disadvantages of the circuit when compared to other full wave rectifier circuit.
b) A full-wave rectifier produces an r.m.s voltage of 10 V at 50 Hz and feeds a resistance of
1,100 Ω and filter uses C = 50 µF. Find the ripple output voltage.
(8M+7M)
5.
a) Explain how transistor acts as an amplifier.
b) Explain the current components of a transistor. Explain early effect. What are the
consequences of early effect?
(7M+8M)
6.
a) Explain the operation of UJT. Define the intrinsic standoff ratio. Draw its characteristic
curve and explain the various parameters.
b) Draw the characteristics and explain the operation of enhancement and depletion mode
MOSFETS.
(8M+7M)
7.
a) What are the factors that affect the stability of operating point? Explain.
b) Discuss the various methods of transistor biasing.
8.
(7M+8M)
a) Explain the h-parameter model of a transistor at low frequencies and derive the formulae for
current gain, input impedance, voltage gain and output impedance.
b) Derive the expressions for current gain, input impedance, output impedance and voltage
gain of a CC amplifier with the help of approximate hybrid model.
(8M+7M)
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Code No: R21026
R10
SET - 2
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRONIC DEVICES AND CIRCUITS
(Com. to EEE, ECE, EIE, ECC, CSE, IT, BME)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) What is magnetic deflection sensitivity of CRT? Derive the magnetic deflection sensitivity
of CRT. What are the salient features of magnetic deflection sensitivity?
b) Explain any three applications of CRO in detail.
(7M+8M)
2.
a) What is meant by distribution function? Plot the Fermi-Dirac probability function verses
energy curves at 00 K and at 30000 K. What is the significance of these plots?
b) Draw the potential energy picture of a metal. Explain qualitatively the presence of potential
barrier at the metal surface.
(8M+7M)
3.
a) Explain the V-I characteristics of Zener diode and distinguish between Avalanche and Zener
Break downs.
b) Discuss about the capacitance effect of a reverse biased P-N junction diode. State it
importance.
(8M+7M)
4.
a) Derive the expression for the ripple factor of π-Section filter when used with a full-wave
rectifier. Make necessary approximations.
b) Compare the performance of Inductor filter, capacitor filter, pi-filter and L-section filter.
(7M+8M)
5.
a) Draw the circuit of a BJT in CE configuration and explain about the input and output
characteristics.
b) A silicon N-P-N transistor with α = 0.995 and ICO=15 nA, operates in the CE configuration.
What is the collector current for a base current of 20µA?
(8M+7M)
6.
a) Explain the various methods to turn on SCR.
b) Explain the construction and operation of N-channel JFET.
(7M+8M)
7.
a) What do you mean by the quiescent point of transistor amplifier? What is a load line?
Explain its significance.
b) Why a transistor needs biasing? Explain.
(8M+7M)
8.
a) Analyze a single stage transistor amplifier using h - parameters.
b) Draw the approximate hybrid model of a transistor amplifier and derive the expressions for
current gain, input impedance, voltage gain and output impedance of a CB amplifier.
(7M+8M)
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Code No: R21026
R10
SET - 3
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRONIC DEVICES AND CIRCUITS
(Com. to EEE, ECE, EIE, ECC, CSE, IT, BME)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) Describe different controls of CRO.
b) Explain the electron gun assembly in CRT.
(8M+7M)
2.
a) What is the meaning of energy density function? Estimate the position of Fermi level in a
conductor having N number of free electrons per cc. Deduce all steps necessary for deriving
the result.
b) What is recombination? Derive the expression for minority carrier lifetime.
(8M+7M)
3.
a) Explain the different current components in a P-N junction diode and hence derive the
current equation.
b) Explain briefly the Varactor and PIN diode.
(5M+10M)
4.
a) Draw circuit diagrams to show two methods of producing a negative output voltage from a
half-wave rectifier. Explain briefly the circuit operations.
b) What is the necessity of having filters in power supplies? Explain with diagrams how R-C
filter improves the output of a rectifier?
(8M+7M)
5.
a) Sketch the typical input and output characteristics of a common base BJT configuration and
explain.
b) In a germanium transistor collector current is 51mA, when base current is 0.4mA.
If hfe = βdc = 125, Calculate cut off current, ICEO.
(7M+8M)
6.
a) With the help of suitable diagrams explain the working of different types of MOSFET.
b) The field effect transistor is called a voltage-sensitive electronic control device. Explain why
is the case?
(7M+8M)
7.
a) Define the stability factors with respect to the changes in ICO, VBE and β. Why is the stability
with respect to changes in VCE not considered?
b) Explain different bias compensation techniques in detail.
(7M+8M)
8.
a) Draw the input and output characteristics of a CE NPN transistor configuration and discuss
how you will determine hie and hfe hybrid parameters from these characteristics.
b) For the emitter follower, with Rs = 0.1 KΩ, RL = 5 KΩ, hfe = 50, hie =1000 Ω, hoe = 25µAV.
Calculate Ai, Av, Avs, Rin and Rout.
(7M+8M)
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Code No: R21026
R10
SET - 4
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRONIC DEVICES AND CIRCUITS
(Com. to EEE, ECE, EIE, ECC, CSE, IT, BME)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) Analyze the motion of electron in and in parallel and perpendicular magnetic field.
b) Derive the expression for electrostatic deflection sensitivity
(8M+7M)
2.
a) Explain the energy band structure of conductor, semiconductor and insulator.
b) What is Hall Effect in semiconductors? The resistivity of doped silicon material is 9 x 103
ohm-m. The Hall coefficient is 3.6 x 10-4 m3 coulomb-1. Assuming single carrier
conduction. Find the mobility and density of charge carriers. e = 1.6 x 10-19 coulomb.
(7M+8M)
a) Explain the operation of a tunnel diode with its energy band diagram.
b) Explain the different current components in a p-n junction diode and hence derive the
current equation .
(8M+7M)
3.
4.
a) Derive the expression for ripple factor, regulation and rectification efficiency of a half-wave
rectifier.
b) What is transformer utilization factor? Determine the rating of a transformer to deliver a 100
Watts of DC power to a load under full-wave rectifier.
(8M+7M)
5.
a) With a neat diagram explain the construction and operation of a BJT.
b) Give the physical arrangement of a PNP transistor and discuss how it provides current
amplification.
(8M+7M)
6.
a) What is channel length modulation in MOSFET? Obtain the output resistance at the Q point.
b) Explain the characteristics of UJT using its equivalent circuit?
(8M+7M)
7.
a) Draw the circuit diagram of a BJT emitter bias and derive the expression of Q point.
Write its advantage over BJT
fixed bias circuit. Also define bias stabilization and stability
factors.
b) In a fixed bias circuit determine IB, IC and VCE if transistor is of silicon, VCC = 10V, RB =2.5
MΩ, RC = 15 KΩ and β = 90.
(8M+7M)
8.
a) Draw and explain the simplified h-parameter model of a common Base amplifier.
b) Compare different transistor amplifier configurations in detail.
(8M+7M)
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