code no: r22041 r10 ii b. tech ii semester supplementary ... · pdf fileii b. tech ii semester...

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Code No: R22041

II B. Tech II Semester Supplementary Examinations May/June - 2015

ANALOG COMMUNICATIONS (Electronics and Communications Engineering)

Time: 3 hours Max. Marks: 75

Answer any FIVE Questions

All Questions carry Equal Marks

~~~~~~~~~~~~~~~~~~~~~~~~

1. a) Describe the operation of switching modulator.

b) Consider a single-tone conventional AM signal with a total power of 1 kW. What is the

power in each of the sideband frequency components if the modulation depth is 70%.

2. a) Explain the operation of ring modulator.

b) What is the effect of carrier frequency incoherence in the process of demodulation of DSB-

SC wave?

3. a) Obtain the Hilbert transform of m(t) = sinc (t).

b) What condition must be the VSB filter transfer function satisfy for distortion-free

transmission?

4. a) Give the main advantage as well as main tradeoff in FM.

b) Compare and contrast single-tone FM and PM.

5. Give a qualitative explanation of the noise performance of the SSB-SC system.

6. Explain the operation of phase modulated FM transmitter.

7. Explain the following terms:

i) Sensitivity ii) Selectivity iii) Image frequency iv) Amplitude limiting

8. Explain the following terms:

i) PAM ii) TDM

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1. a) A signal m (t) = 10 cos (2π 103t) amplitude modulates a carrier. If the bandwidth of the

transmitted signal has to be less than 2% of the carrier frequency, what should the carrier

frequency be?

b) Describe the operation of envelope detector.

2. a) Why was DSB-SC modulation scheme not adopted for commercial voice/music signal

broadcasting? Explain.

b) Explain the operation of balanced modulator.

3. a) Is it possible to generate an SSB signal that can be detected by a linear envelope detector?

Explain.

b) Explain the phase-shift method of SSB-SC generation.

4. a) Explain the direct method of FM generation.

b) Explain how an envelope detector can be used to demodulate an FM signal.

5. Explain why the noise performance of an AM system using synchronous detection is superior

to that of an AM system using envelope detection.

6. Explain the operation of variable-reactance type FM transmitter.

7. Explain the operation of superheterodyne receiver.

8. a) Explain the process of generation of PAM signals.

b) Distinguish between FDM and TDM.

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1. a) Determine the power efficiency of the amplitude modulated wave:

s (t) = [2 + cos (50πt)] cos (20000πt)

b) Sketch the magnitude spectrum of a conventional AM signal with carrier frequency 1MHz

and the message signal frequency 1 kHz.

c) What is the need for modulation? Explain.

2. a) Explain the working of a product modulator.

b) What is quadrature-null effect? Explain.

3. Derive an expression for canonical representation of USSB signal.

4. a) Show that FM is more immune to nonlinear distortion than AM.

b) Why does FM, in general, require much larger bandwidth than AM?

5. Derive the expression for the output SNR for an ideal baseband communication system. State

the assumptions involved.

6. a) Explain the operation of AM transmitter.

b) Write notes on frequency stability in FM transmitters.

7. a) Why are many RF amplifiers used in TRF receiver? Explain.

b) Explain the principle of operation of super heterodyne FM receiver.

8. a) Explain the operation of PWM generator.

b) Describe the demodulation of PPM waves.

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1. a) Derive an expression for effective modulation index for multi-tone modulation.

b) Describe the operation of square-law modulator.

2. a) Describe the operation of Costas loop receiver.

b) Give the working principle of a squaring synchronizer.

3. a) Describe the filter method of SSB signal generation.

b) Distinguish between different amplitude modulation schemes.

4. a) Give the details of the frequency and bandwidth of the signals used in commercial FM radio

broadcasting. What is Carson’s rule?

b) Show how a PM signal can be demodulated using an FM demodulator.

5. Explain pre-emphasis and de-emphasis circuits.

6. a) Give the classification of radio transmitters.

b) What is the effect of feedback on performance of AM transmitter? Explain.

7. In the context of radio receivers, define the terms:

a) selectivity

b) sensitivity

c) image frequency rejection ratio

d) Q-factor

8. Write notes on the following terms:

a) Dual polarity PAM

b) Demodulation of PWM signals

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Code No: R22026

II B. Tech II Semester Supplementary Examinations, May/June - 2015

CONTROL SYSTEMS (Com. to EEE, ECE, EIE, ECC, AE)


Answer any FIVE Questions All Questions carry Equal Marks

~~~~~~~~~~~~~~~~~~~~~~~~

1. a) Describe the closed loop control system with an examples

b) Obtain the mathematical model of the following system

2. a) How do you represent a control system by the block diagram and illustrate with an example.

b) Derive the transfer function and develop the block diagram of armature controlled DC servo

motor

3. a) List different types of standard test signals used in time response analysis

b) The open loop transfer function of a unity feedback system is characterized

)6.01)(3.01(

1)(

ssssG

++= .

Find the steady state error for unity step, unity ramp and unity acceleration inputs. Also find

the damping factor and natural frequency of dominant roots.

4. a) Define and derive the break away point on the root locus

b) The open loop transfer function of unity feedback system given by G(s) =)Ts8s(S

K

2++

.

Using Routh’s criterion, determine the values of K and T. which will correspond to a stable

system.

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5. Sketch the bode plot and determine the following

i) gain cross over frequency ii) phase cross over frequency

iii) gain margin iv) phase margin

for the transfer function is given G(s) = )2s()1s(s

K

++ and determine the K for stability.

6. a) State and explain the Nyquist stability criterion

b) Draw the polar plot for the transfer function G(s)= )31)(1(

12

sss ++ . Determine the

frequency at which the plot crosses the real axis and the corresponding )j(G ω .

7. a) What is the need of lag- lead compensator? Derive its transfer function and draw the bode

plot

b) Explain the design procedure for PID controller compensation in frequency domain

8. a) Develop the state model of linear time invariant systems

b) Determine the state controllability and observability of the following system

−

−=

40

01A ,

=

1

0B , [ ]31=C

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1. a) Explain the need of Electrical analog systems

b) Determine the transfer function for the mechanical system shown in below figure

2. a) Explain the construction and operation principle of synchro transmitter and

b) Find the transfer function for the following block diagram using Mason’s gain formula

3. a) What is mean by step, ramp, parabolic and impulse inputs

b) A unity feedback system is characterized by an open loop transfer function G(s)= )5( +ss

K.

Find the gain K so that the system will have a damping factor of 0.6. For this value of K,

determine the natural frequency of the system. It is subjected to a unity step input. Also

determine the closed loop response of the system in time domain.

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4. a) Explain the special cases in Rouths stability criterion

b) Sketch the root locus for a given units feedback control system whose open loop transfer

function is G(s) = )73( 2

++ sss

k

5. Sketch the Bode plot and determine the following

gain cross over frequency

phase cross over frequency

gain margin

phase margin

for then transfer function is given G(s) = )508(

)2.01(102

++

+

sss

s

6. a) Illustrate the effect of adding a pole or zero to a transfer function on its polar plot

b) A unity feedback control system has an open loop transfer function given by

G(s) H(s) = )2s)(5s(s

100

++ Draw Nyquist diagram and determine stability

7. Design a phase lag network for a plant with the open loop transfer function G(s)= 2)2.01(

120

ss +

to have a phase margin of 350. Verify the performance of the compensated system with the

specification.

8. a) State and explain the controllability and observability of a system

b) Reduce the matrix A to diagonal matrix, A =

−

−

21

23

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1. a) Explain the Reduction of parameter variation by feedback

b) Obtain the differential equations of mechanical system shown in below figure. Also draw the

electrical analogy circuit based on force current analogy.

2. a) Describe the synchro pair as error detector with circuit diagram

b) Using block diagram reduction technique, find the transfer function from each input to the

output C

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3. a) Briefly discuss the different types of controllers

b) A unity feedback control system has a loop transfer function, G(s) =)2(

10

+ss. Find the rise

time, percentage overshoot, peak time and settling time for a step input of 12 units.

4. A unity feedback system has an open loop function G (s) = )94( 2

++ sss

k make a rough sketch

of root locus plot by determining the following (i) Centroid, number and angle of asymptotes

(ii) angle of departure of root loci from the poles (iii) Breakaway points if any (iv) points of

intersection with jω axis and (v) maximum value of k for stability

5. a) Define frequency domain specifications

b) Determine the resonant frequency ωr, resonant peat MP and bandwidth for the system whose

transfer function is G(jω)= 2)(25

5

ωω jj ++

6. The open loop transfer function of unity feedback system is G(s) = )2s)(1s(s

1

++ . Draw the

Nyquist plot test the stability. Also find gain margin and phase margin.

7. A unit feed back system has an open loop transfer function G(s) = )12.0)(1( ++ sss

K. Design a

phase lag compensator to meet the following specifications:

Velocity error constant = 8

Phase margin ≥ 30o

8. a) States and prove the properties of state transaction matrix

b) Determine the state model of the system for the following transfer function

)s(

)s(

U

Y =

4s11s6s

5ss2

23

2

+++

++

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1. a) What do you mean by the sensitivity of the control system and discuss the effect of feedback

on sensitivity

b) Obtain the electrical analogous mechanical system shown in below figure in force current

analogy.

2. a) What is the difference between AC servo motor and induction motor?

b) Using block diagram reduction technique, find the closed loop transfer function of the

following system.

3. a) Define the steady state error and error constants of different types of inputs

b) The open loop transfer function of unity feedback system is given by G(s)=)Ts1(s

K

+

By what factor should the amplifier gain K be multiplied so that the damping ratio is

increased from 0.25 to 0.75.

By what factor should K be multiplied so that the maximum overshoot of step response is

reduced from 80% to 20%.

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4. a)What is the necessary and sufficient conditions of stability for linear time invariant systems

b) Sketch the root locus plot of unity feed back system with an open loop transfer function

G(s) = )3)(1( ++ sss

K. Find the range of K for the system to have damped oscillatory

response. Determine the value of K so that the dominant pair of complex poles of the system

has a damping ratio of 0.4. Corresponding to this value of K. Find the closed loop transfer

function in the factored form.

5. Sketch the Bode plot and determine the following

Gain cross over frequency

Phase cross over frequency

Gain margin

Phase margin,

For the transfer function is given by

G(s) = )5.01()2.01(

)1.01(50

ss

s

++

+

6. a) Explain the procedure for constructing the polar plots

b) Draw the Nyquist plot for a given transfer function

G(s) = )1s)(1s(

)2s(

−+

+

7. Consider a unity feedback system with open loop transfer function G(s)= )2.01)(1( sss

K

++,

design a suitable compensator so that the compensated system has

Kv = 7 sec-1

Phase margin = 450

Gain margin ≤ 10 db

8. a) List out the merits and demerits of state variable techniques

b) The state equations of LTIV is represented by x = Ax + Bu. Find the state transition matrix.

A =

−

−

−

100

110

002

, B =

0

1

0

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Code No: R22043


ELECTRONIC CIRCUIT ANALYSIS

(Com. to ECE, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~

1. a) For the amplifier shown in figure1, calculate Ri; Ro; AV ;AVS and AI = - I2 / I1.

The h-parameter values are hfe = 50, hie = 1.1K, hre = 2.5x10 - 4, hoe = 24 µA/V.

b) What is square law distortion? what is its effect in FET amplifiers? Compare important

characteristics of CD, CS, and CG FET amplifiers.

2. a) An amplifier has a voltage gain of 200, before negative feedback is applied. When negative

feedback with β-0.25 is applied, the nomial gain changes by 10%.Find the percentage

change in the overall gain?

b) With the help of a suitable BJT based voltage series feedback amplifier diagram, explain the

features and benefits of negative feedback in amplifiers.

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3. a) Draw the circuit diagram of colpiit’s oscillator and explain its operation ?

b) Find an expression for the frequency of oscillations in wein bridge oscillator. Show that the

amplifier used in a wein bridge oscillator must have a gain greater than 3 for sustained

oscillations ?

4. a) Mention the multi-stage amplifiers that exhibit very large input impedance. Describe the

operation of any one such cascaded set through relevant schematic and mathematical

expressions.

b) Four identical cascaded stages have an overall upper 3-dB frequency of 20 KHz and a lower

3-dB frequency of 20 Hz. What are fL and fH of each stage? Assume non interacting stages?

5. a) Derive various Resistive parameters of Hybrid π model of a transistor in terms of h

parameters.

b) What is the relationship between fT and fβ? Discuss the significance of fT .

6. a) Draw the circuit of class-A series fed power amplifier and derive the expression of output

power Po.

b) Draw and discuss the operation of class – C power amplifier?

7. a) Draw the circuit diagram of a double tuned amplifier and derive the expression for 3 db band

width ?

b) Describe the heat sinks for tuned power amplifiers?

8. a) Explain why voltage regulators are required for a DC power supply operating from an AC

source?

b) A power supply has a voltage regulation of 1% If the no load voltage is 30V. What is the full

load voltage?

c) Give the differences between Load and Line Regulations.

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ELECTRONIC CIRCUIT ANALYSIS (Com. to ECE, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~

1. a) Discuss the effect of each and every component of a CE amplifier that has an influence on

the frequency response of the amplifier

b) Draw the circuit diagram and equivalent circuit of a Common Source amplifier. Derive

expressions for AV , AI , RIN and ROUT without source and load resistances

2. a) Derive the expression for voltage gain ,input resistance ,output resistance of the current

shunt feedback amplifier?

b) An amplifier has a voltage gain of 500,f1=100Hz,f2=400Khz and a distortion of 10%

without feedback. Determine the amplifier voltage gain f1f,f2f and Df when a negative

feedback is applied with feedback ratio of 0.01

3. a) Substantiate the requirement of positive feedback in amplifier for oscillations.Relate the

requirement to Barkhausen Criterion.

b) With the help of neat circuit diagram, explain how sustained oscillations are obtained in RC

phase shift BJT based oscillator. Derive the expression for frequency of oscillation

4. a) Derive expressions for overall voltage gain and overall current gain of a two-stage RC

coupled amplifier.

b) List out the special features of Darlington pair and cascode amplifiers.

5. a) In Hybrid π model of a transistor at high frequencies, show that gm is pro-portional to the

collector current.

b) Define fT and what is physical significance of fT ? If a silicon p-n-p transistor has an

fT = 400MHz. What is the base thickness? Assume Diffusion constant as 13 cm2/sec.

6. a) Certain power transistor for class A operation has a zero signal power dissipation of

20Watts. If the AC output power is 5W, find

i) Collector efficiency and ii) Power rating of the transistor

b) Classify the large signal amplifiers based on its operating point? Distinguish these

amplifiers interms of conversion efficiency ?

7. a) Derive the equation for the 3dB bandwidth of double tuned amplifier?

b) Write short notes on different stabilization methods in tuned amplifiers.

8. a) Describe the functioning of an IC 723 in shunt regulator configuration. Compare series and

shunt regulation configurations specifically with IC 723.

b) Explain the significance of Low Pass Filter in Switching Regulator

c) What are the limitations of Switching Regulators?

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ELECTRONIC CIRCUIT ANALYSIS (Com. to ECE, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~

1. a) Draw a circuit diagram of a emitter follower transistor amplifier and derive the expressions

for voltage gain ,input resistance and ouput resistance ?

b) Discuss the effect of different types of loads to a common source MOS amplifier.

2. a) The β and the open loop gain of an amplifier are -10% and -80 respectively. By how much

% the closed loop gain changes if the open loop gain increases by 25%?

b) Compare the characteristics of feedback amplifiers in all the four configurations.

c) Reason out why 2 stages are required to implement current shunt feedback?

3. a) Differentiate between RC and LC type oscillators.

b) Derive the expression for frequency of oscillation in a Hartley Oscillator.

c) State Barkhausen Criterion for Oscillations

4. a) Differentiate between direct and capacitive coupling of multiple stages of amplifiers. With

the help of a neat circuit diagram, describe the working of a cascade amplifier.

b) Draw the circuit diagram, equivalent circuit of a Darlington pair and derive expressions for

overall voltage gain and input impedance.

5. a) What is the frequency range to consider Giacolletto model of a transistor at high

frequencies? What is the significance of fT in discussing the frequency range of a transistor

at high frequencies?

b) Explain emitter follower at high frequencies?

6. a) A single stage class A amplifier Vcc

=20V, VCEQ

=10V, ICQ

=600mA, RL=16 Ω. The ac output

current varies by ± 300mA, with the ac input signal. Find

i) The power supplied by the dc source to the amplifier circuit.

ii) AC power consumed by the load resistor.

iii) AC power developed across the load resistor.

iv) DC power wasted in transistor collector.

v) Overall efficiency

vi) Collector efficiency.

b) What is crossover distortion? How do we eliminate this distortion? What are the advantages

of class B over class A power amplifier?

7. a) Draw the circuit diagram of a double tuned amplifier and derive the expression for 3 db band

width ?

b) Describe the heat sinks for tuned power amplifiers?

8. a) Draw the circuit diagram of a series voltage regulator that can implement current limiting in

addition to regulation. Explain its operation with the help of its load V-I characteristic.

b) Compute the output voltage of a 24 V regulator designed to limit the maximum current to

0.1A when connected to a load resistance of i) 1K ii) 100 K

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ELECTRONIC CIRCUIT ANALYSIS

(Com. to ECE, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~

1. a) For the CB amplifier circuit shown, compute RIN

and ROUT

if C1

is

i) Connected ii) Not connected

The h-parameters of the transistor in CE configuration are listed as:

hie

= 2.1KΩ, hfe

= 81, hoe

= 1.66 µMhos and hre

is negligibly small.

b) State Miller’s theorem. Specify its relevance in the analysis of a BJT amplifier.

2. a) An amplifier has a gain of 50 with negative feedback. For a specified output voltage, if the

input required is 0.1V without feedback and 0.8V with feedback, Compute β and open loop

gain.

b) Through the block schematics, show four types of negative feedback in amplifiers.

3. a) List out the merits and demerits of oscillators.

b) With the help of suitable schematic and description, show that both positive and negative

feedback are used in a Wien Bridge oscillator. Establish the condition for oscillations

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4. a) If four identical amplifiers are cascaded each having fH =100 KHz, determine the overall

upper 3dB frequency f h*

Assume non interacting stages.

b) Write a short note on Bootstrapped Darlington circuit.

5. a) Show that in Hybrid model, the diffusion capacitance is proportional to the emitter bias

current.

b) How do the parameters of hybrid-π model transistors vary with temperature?

6. a) Derive the expression for maximum conversion efficiency for a simple series fed Class A

power amplifier.

b) What are the drawbacks of transformer coupled power amplifiers?

c) A push pull amplifier utilizes a transformer whose primary has a total of 160 turns and

whose secondary has 40 turns. It must be capable of delivering 40W to an 8 Ω load under

maximum power conditions. What is the minimum possible value of Vcc

?

7. a) Compare single tuned inductively coupled amplifier with capacitively coupled single tuned

amplifier? Highlight their merits.

b) What is a tank circuit? What are the advantages of using tank circuit as a load to an

amplifier?

8. a) Draw the transistor based shunt voltage regulator and describe its functioning. Justify the

statement that current limiting is an inherent feature of shunt voltage regulators

b) Why switching frequencies are limited in Switching regulator and also explain how to

overcome this.

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Code No: R22042


ELECTRO MAGNETIC WAVES AND TRANSMISSION LINES (Com. to ECE, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~~

1. a) State and Explain coulomb’s law.

b) Two dipoles with moments -5 az nC/m and 9 az nC/m are located at points (0, 0, -2) and

(0, 0, 3) respectively. Find the potential the origin. (8M+7M)

2. a) State and explain Biot – Savart’s law.

b) State Maxwell’s equations for magneto static fields. (8M+7M)

3. a) Distinguish the terms transformer EMF and Motional EMF.

b) A parallel plate capacitor with plate area of 5 cm2

and plate separation of 3 mm has a voltage

50 sin 103t V applied to its plates. Calculate the displacement current assuming ɛ = 2ɛ0.

(8M+7M)

4. a) Define the term attenuation constant and derive the expression for it..

b) In a non magnetic medium E = 4 sin (2π X 107

t – 0.8x) az V/m. Find ɛr , η . (8M+7M)

5. a) State and prove poynting theorem.

b) Define the term “plane of incidence” and give the significance of it. (10M+5M)

6. Explain the following terms in detail.

a) Wave impedance

b) Phase and group velocities (8M+7M)

7. a) List out different types of transmission lines and write the applications of transmission lines.

b) A transmission line has operating at 500 MHz has Zo = 80 Ω, α = 0.04 Np/m, β = 1.5 rad/m.

Find the line parameters R, L, G and C. (8M+7M)

8. a) Derive the expressions for the input impedance of a transmission line.

b) A certain transmission line 2 m long operating at ω = 106

rad/s has α = 8 dB/m, β = 1 rad/m,

and Z0 = 60 + j40 Ω. If the line is connected to a source of 0010∠ V, Zg = 40 Ω and

terminated by a load of 20 + j50Ω, determine the input impedance. (8M+7M)

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1. a) State and Explain Gauss law. Write the applications of Gauss law.

b) Point charges 1mC and -2mC are located at (3, 2, -1) and (-1, -1, 4) respectively. Calculate

the electric force on a 10 nC charge located at (0, 3, 1) and electric field intensity at that

point. (8M+7M)

2. a) Derive the expression for magnetic field due to a straight filamentary conductor carrying

current I.

b) Define the term Magnetic flux density and explain why isolated magnetic pole does not

exist. (8M+7M)

3. a) Explain the inconsistency of Ampere’s circuit law.

b) Write the expression for Maxwell equations for Time Harmonic EM fields. (8M+7M)

4. a) Discuss about wave propagation in Good conductors.

b) The magnetic field component of a wave is given by H = 30 cos (108t – 6x) ay mA/m.

Determine

i) Direction of wave propagation

ii) The wavelength

iii) The wave velocity. (8M+7M)

5. a) Derive an expression for reflection coefficient when a wave is incident on a dielectric

obliquely with parallel polarization.

b) Explain the terms Brewster and critical angles. (8M+7M)

6. Derive the expressions for the E and H field components for TM waves in a parallel plane

wave guide. (15M)

7. a) Define the term characteristic impedance and derive the expression for it.

b) A distortion less line has Zo = 60 Ω, α = 20 mNp/m, u = 0.6c, where c is the speed of light in

vacuum. Find the line parameters R, L, G, C at 100 MHz. (8M+7M)

8. a) Explain how the smith chart is constructed.

b) Sketch the variation of input impedance of lossless transmission line with electrical length

when it is i) Open circuited and ii) Shorted line (8M+7M)

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1. a) Derive the relationship between electric field intensity and electric potential.

b) If J = 3

1

r

(2 cos θ ar + sin θ aθ) A/m2, calculate the current passing through

i) A hemispherical shell of radius 20 cm, 0 < θ < π/2, 0 < Ф < 2π

ii) A spherical shell of radius 10 cm (8M+7M)

2. a) A circular loop located on x2

+ y2

= 9, z = 0 carries a direct current of 10 A along aФ.

Determine H at (0, 0, 4) and (0, 0 -4).

b) Derive the expression for magnetic field due to Infinite line current using Ampere’s circuit

law. (8M+7M)

3. a) Define the term displacement current density and give the significance of this term.

b) Write the Maxwell’s equations for static fields. (8M+7M)

4. a) Show that when a uniform plane wave propagating in particular direction, it does not contain

any field components in that particular direction.

b) A uniform plane wave in air has E = 10 cos (2π X 106

t – βz) ay V/m. Calculate β, λ and H.

(8M+7M)

5. a) Determine the Expression for Electric field of plane wave when it is incident on a perfect

conductor normally.

b) Obtain an expression for power loss in a plane conductor in terms of surface resistance.

(8M+7M)

6. Derive the expressions for the E and H field components for TE waves in a parallel plane wave

guide. (15M)

7. a) What are the primary and secondary constants of transmission lines. Give the expressions for

these constants.

b) A telephone line has R = 30 Ω/km, L = 100 mH/km, G = 0, and C = 20 µF/km. At f = 1

KHz, find the characteristic impedance of the line and propagation constant. (8M+7M)

8. a) Define the terms reflection coefficient and derive the expression for it.

b) Write the applications of smith chart. (8M+7M)

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1. a) Define the term electric potential and hence deduce the expression for electric potential at

any point due to point charge located the origin.

b) The point charges -1 nC, 4 nC and 3 nC are located at (0, 0, 0), (0, 0, 1) and (1, 0, 0)

respectively. Find the energy in the system. (8M+7M)

2. a) State and explain ampere’s circuit law.

b) Derive the expression for magnetic field due to Infinite sheet of current using Ampere’s

circuit law. (8M+7M)

3. What is meant by boundary conditions? Derive the boundary conditions for electrostatic fields.

(15M)

4. a) Discuss about wave propagation in free space.

b) Define the term loss tangent and give the significance of it. (8M+7M)

5. a) Determine the Expressions for Electric fields of plane wave when it is incident on a perfect

dielectric normally.

b) List out various applications of poynting theorem. (8M+7M)

6. a) Explain why TEM wave propagation does not exist in wave guides.

b) Sketch the electric and magnetic fields in a parallel plate and coaxial lines. (8M+7M)

7. a) Discuss about distortion less transmission lines.

b) Draw the π – type and T – type equivalent circuits of transmission lines. (8M+7M)

8. a) Explain about low loss transmission lines.

b) Explain the procedure for finding reflection coefficient and standing wave ratio using smith

chart. (8M+7M)

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Code No: R22021


PULSE AND DIGITAL CIRCUITS (Com. to EEE, ECE, ECC, BME, EIE)

Time: 3 hours Marks: 75



~~~~~~~~~~~~~~~~~~~~~~~~

1. a) Draw the circuit of a double differentiator and derive the output for input vi = V e-t/τ

and

also plot the response and also locate maxima and minima.

b) Derive the expressions for the output of a RC Low pass circuit and also draw the input

and output waveforms for the following: (i) ramp input. (ii) sinusoidal input.

2. a) For the circuit shown in Figure 1, draw the transfer characteristics when diodes are ideal

diodes.

b) Derive the expression for steady state output of a clamper circuit when excited by a

square wave input and also sketch the steady state output to scale.

3. a) A transistor has fT = 50 MHZ, hFE = 40, cb’c = 3pF and operates with Vcc = 12 V and Rc =

500 Ω. The transistor is operating initially near to cut-in point. What base current must be

applied to drive the transistor to saturation in 1 µsec?

b) Draw the circuit of a two input ECL NOR gate and explain its operation.

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Code No: R22021

4. a) Explain the hysteresis that exists in Schmitt trigger circuit.

b) Draw the circuit diagram of a Schmitt trigger circuit and explain its operation.

5. a) Design a collector coupled transistor monostable multivibrator to produce a time delay of

50 µ sec. Given that hFE = 100 and driven by ± 15V power supply, VCE sat = 0.3V,

VBE sat = 0.7 V, VBE cut off = 0 V.

b) Explain how an Astable multivibrator can be used as voltage to frequency converter.

6. a) In a bootstrap time base generator , find the values of RB and Cs to generate a 15 V sweep

in 250 µ s.

b) Draw the circuit of current time base generator and explain its operation.

7. a) With the help of waveforms, show that the frequency division is by a factor of two in a

sweep generator.

b) Compare sine wave synchronization with pulse synchronization.

8. a) Explain the operation of a blocking oscillator and also enlist the applications of the

blocking oscillator.

b) Draw the circuit of a triggered transistor monostable blocking oscillator with base timing

and explain its operation and derive expression for its output pulse width.

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1. a) Derive the expressions for the output of a RC High pass circuit and also draw the input and

output waveforms for the following : (i) sinusoidal input. (ii) pulse input.

b) A 10V step input is applied to an RC low pass circuit with R = 22kΩ and C = 300 pF.

Calculate the rise time of the capacitor voltage, the time required for the capacitor to

charge up to 63.2% of its maximum charge. And the time taken for the capacitor to become

completely charged.

2. a) Explain the principle of clamping, and discuss the effects of source impedance, load

resistance and cut-in voltage on clamping.

b) Draw the transfer characteristics for the circuit shown in Figure 1.

3. a) Explain the reverse recovery of a semiconductor diode and also explain how the diode

speed is affected by the recovery time.

b) Compare the DTL, ECL, TTL and CMOS logic families.

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Code No: R22021

4. a) Draw the circuit diagram of fixed amplitude sweep circuit and explain its operation.

b) Design a collector coupled bistable multivibrator to operate from a ± 6V power supply.

Using npn transistor having hfe = 70 and ICE sat = 2 mA

5. a) In a collector coupled astable circuit using pnp transistor VCC = 15 V, Rc = 3 KΩ, R1 = 40

KΩ, R2 = 20 KΩ, hfe = 30, rbb’ = 0 and neglect all forward biased junction voltages.

Calculate and plot the waveforms at the base and collector of one transistor and also find

the value of coupling capacitor when the circuit is working at 5 KHz, assuming C1 = C2.

b) Explain how a monostable multivibrator works as a voltage to time converter using

suitable waveforms and circuit.

6. a) Enlist and explain the general features of a time-base signal. And also explain why time

base generators are called sweep circuits.

b) With help of neat sketches explain the working of a bootstrap time base generator.

7. a) Explain how a sinusoidal oscillator can be used as a frequency divider.

b) Using suitable sketches explain the process of synchronization of monostable multivibrator.

8. With the help of circuit diagram and relevant waveforms explain the operation of a triggered

transistor blocking oscillator with base timing. Derive the expression for the pulse width at the

output. Also explain the disadvantages of the circuit and state how they can be overcome.

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1. a) In a RC high pass circuit, derive the expression for percentage tilt.

b) A 5 KHz idle square wave is applied to a RC circuit whose output has tr = 250 ns and

percentage tilt of 5%. Determine the upper and lower 3 – dB frequencies of the circuit.

2. a) With the help of a neat circuit diagram, explain the working of an emitter – coupled clipper.

b) With the help of a neat circuit diagram, explain the working of a simple diode comparator.

Draw the output waveform for a ramp input.

3. a) Briefly explain about transistor switching times.

b) With the help of neat diagrams explain the working of a TTL NAND gate.

4. a) Design a fixed bias Bistable multivibrator using npn silicon transistor for the following

specifications: VCC=VBB=12V, hfe(min)=20, ic(sat)=5mA, VCEsat=0.3V, VBE sat= 0.7V

b) Explain how Schmitt trigger can be used as a comparator using relevant sketches.

5. a) Explain how Astable multivibrator can be used as voltage controlled oscillator.

b) Design a collector coupled monostable multivibrator with an output amplitude of 10 V of

time period 20 µ sec , IC(sat) = 8 mA, the base drive required for the ON transistor is 1.5

times iB(min), VCE(sat) = o.1V, VBE(sat) = 0.3V, hfe(min) = 20.

6. a) What are the reasons for nonlinear sweeps and also explain the different methods of

improving linearity in these circuits.

b) Design a bootstrap sweep generator using following transistor parameters, hfe(min) = 20, Vcc =

15V, ic = 1 mA

7. a) Using suitable sketches explain the process of synchronization of astable multivibrator.

b) Write short notes on the following:

i) Phase delay. (ii) phase jitters

8. a) Draw the circuit of a four diode sampling gate and explain its operation.

b) Explain the working of astable transistor blocking oscillator with wave forms.

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1. a) Explain in detail with suitable waveforms about how an RC High –pass circuit can be

used as differentiator.

b) Derive the expression for the output of a series RLC circuit when excited by step input

and also draw the output waveforms.

2. a) For a diode shunt clipper with ideal diode characteristics and VR = 15 V and Vi = 30

sinωt, draw to scale the input and output waveforms and label the maximum and minimum

values for the following cases: (i) R = 10 kΩ , (ii) R = 20 KΩ

b) Explain the principle of clamping. What is the need for a shunting resistor R in parallel

with the diode in the basic clamping circuit?

3. a) Explain in detail the various switching times of the transistor supported by their

expressions.

b) With help of neat sketch explain the operation of a two input CMOS NAND gate.

4. a) Explain the transfer characteristics of Schmitt Trigger. Explain how hysteresis can be

eliminated.

b) Discuss in detail about the symmetrical and asymmetrical triggering of bistable

multivibrator.

5. a) Derive an expression for the output gate width of a transistor monostable multivibrator.

b) Design a collector coupled astable multivibrator for the following specifications, f =10 KHz,

Vcc = 9 V, hfe = 20, iC(max) = 2 mA.

6. a) Design a transistor bootstrap time base generator triggered by a negative pulse of amplitude

5 V and duration 2 m sec separated by 0.2 msec, generating an output of 10 V with time

period of 2 m sec. The load resistance is 2 KΩ and the ramp is linear within 1%. Supply

voltage is ± 12 V and hfe (min) = 120.

b) Compare voltage time base generator circuits and current time base generator circuits.

7. a) Explain the principle of synchronization and synchronization with frequency division.

b) A Symmetrical astable multivibrator using transistor operates from 10 V supply has a

period of 1 m sec. Triggering pulses of spacing 750 µ sec are applied to one base through a

small capacitor from a high impedance source. Find the minimum triggering pulse

amplitude required to achieve 1:1 synchronization.

8. a) Compare monostable triggered transistor blocking oscillator (base timing) and monostable

triggered transistor blocking oscillator (emitter timing).

b) Why is the pulse width of transistor blocking oscillator (employing base timing) highly

sensitive

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Code No: R22023


SWITCHING THEORY AND LOGIC DESIGN

(Com. to EEE, ECE, ECC, BME, EIE)




~~~~~~~~~~~~~~~~~~~~~~~~ 1 a) Explain how decimal numbers are represented in binary, octal and

hexadecimal

[6]

b) Find the X from the following? (i) (B0.D)16 = (X)8 (ii) (3.33)3 = (X)2 [6]

c) Consider an arbitrary number system with the independent digits as 0, 1 and

X. What is the radix of this number system? List the first 10 numbers in this

number system.

[3]

2 a) Express the compliment of following functions in sum of min terms

i) F(A,B,C,D) = ∑ (1,3,5,6,12,14) ii) F(x,y,z) = π (0,2,6,5)

[8]

b) Find the compliment of F = x+yz then show that F.F` = 0 and F + F` = 1 ? [3]

c) Show that the dual of an exclusive OR is equivalent to its complement

[4]

3 a) Simplify the Boolean function F together with the don’t care conditions d in

(i) sum of products and (ii) product of sums using K-maps

f(w,x,y,z) = ∑ (0,2,3,8,10,12)

d(w,x,y,z)= ∑ (1,5,6,11,14)

[12]

b) Simplify the following function f = x`y` +yz + x`yz`

[3]

4 a) Draw the circuit diagram of a 4-bit adder-subtractor and briefly describe its

functionality?

[8]

b) Draw the logic diagram of a three digit BCD adder and briefly describe its

functional principle.

[7]

5 a) Realize the switching function f (w,x,y,z)= ∑ (1,5,6,8,9,11,14) by

an (8 × 1) multiplexer.

[7]

b) Realize NOT,AND,NOR,NAND,NOR and XOR gates using 2X1

Multiplexer

[8]

6 a) Write short notes on PLA. [3]

b) Implement 4 bit binary to gray code conversion logic functions in PLA. [7]

c) Give the comparison between PROM, PLA and PAL.

[5]

7 a) Develop a synchronous 3-bit UP/DOWN counter with a gray code sequence.

The counter should count UP when an UP/DOWN control i/p is 1. And count

DOWN when i/p is 0.

[8]

8 a) What are the capabilities and limitations of Final State Machines? [8]

b) Explain in detail the Mealy state diagram and ASM chart for it with an

example.

[7]

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1 a) Represent the number 6027 in BCD & EXCESS-3 code? [3]

b) If A = -57 and B = +38 Represent A and B in 8-bit 2’s complement.

Find i) A+B ii) A-B using 2’s complement method [7]

c) convert the binary number to hexadecimal 10110001101011.11110010 [2]

d) Using 8-bits represent the integers -48 and 52 in

(i) Signed magnitude form

(ii) Twos complement form

[3]

2 a) Express the following functions in sum of minterms and product of

maxterms

i) f(A,B.C.D) = B`D + A`D + BD

ii) f (x,y,z) = (xy+z)(xz+y)

[7]

b) Explain how hamming code is constructed for single bit error detection and

correction with example

[8]

3 a) Realize a network whose input are first 10 non-negative integers x in the

Gray code, and whose output has the value 1 when 5 ≤ x ≤ 7.

[8]

b) Minimize the following function using K-map

F=∑(0,2,4,5,6,7,8,10,14,17,18,21,29,31) +∑d(11,20,22)

[7]

4 a) Implement a parallel adder to perform addition between two 8 bit numbers

100111002 and101111012 ? Explore the result when the input carry at

lowest bit is 0 and 1.

[8]

b) Explain on look ahead carry adder operation with diagram?

[7]

5 a) Design 3 to 8 line decoder circuit using NOR gates only. [12]

b) Explain different hazards in combinational circuit

[8]

6 a) Give the comparison between PROM, PLA and PAL.

[8]

b) Write the programming table to implement BCD to using a PLA?

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Code No: R22023

7 a) Derive the state tables for the 4 bit ring counter [8]

b) Explain the working of 3-bit bi-directional shift register with the help of

diagram?

[7]

8 a) For the state table of the machine given below. Find the equivalent

partition and a corresponding reduced machine in standard form.

Present State Next State Z

x=0 x=1

A D,0 H,1

B F,1 C,1

C D,0 F,1

D C,0 E,1

E C,1 D,1

F D,1 D,1

[15]

b)Design the above using JK flip-flops [10+5]

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1 a) Perform the subtraction with the following unsigned decimal numbers by

taking the 2’s complement of subtrahend

i) 11010-10000 ii) 11010 -1101 iii) 100 – 110000 iv) 1010100-1010100

[7]

b) Convert the decimal number 416.75 to base 7, 8 and 12

[8]

2 Explain the following codes

a) Gray code

b) Weighted Codes

c) Hamming code [5+5+5]

[15]

3 Simplify the following using K-map method and tabulation method

F( A,B,C,D,E)=_(0,1,2,5,8,11,13,16,17,21,23,25,29,31)

[15]

4 a) Realize a network that activates the seven-segment display of first 10 non-

negative integers as shown

[8]

b) Draw the logic diagram of a three-digit Excess-3 adder and briefly describe

its functional principle?

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Code No: R22023

5 a) An 8X1 multiplexer has inputs A, B, and C connected to S2,S1, and S0,

respectively. The data inputs, I0 through I7, are as follows: I1 = I2 = I7 = 0; I3

= I5 = 1; I0 = I4 =D and I6= D`. Determine the Boolean function that the

multiplexer implements.

[12]

b) Construct 5X32 decoder with four 3X8 decoders with enable and one 2X4

decoder. Use block diagrams.

[3]

6 a) Obtain the programmable table for three digit binary to excess-3 code

conversion using PLA and implement it using PLA

[9]

b) Implement Full adder circuit using ROM

[6]

7 a) The content of a 4 bit shift register is initially 1101. The register is shifted

six times to the right, with the serial input being 101101 what is the content

of the register after each shift?

[7]

b) Design a mod-11 counter using the +ve edge triggered JK Flip-Flop

[8]

8 a) Convert the following mealy machine into a corresponding Moore machine?

PS NS,Z

X=0 X=1

A C,0 B,0

B A,1 D,0

C B,1 A,1

D D,1 C,0

[8]

b) Design the circuit for the above table [7]

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1 a) Explain weighted and non- weighted codes with example [7]

b) Represent the decimal number 6456 in

i) BCD code ii) excess-3 code iii)2421 code iv) 6311 code

[8]

2 a) A 12 bit hamming code word containing 8 bits of data and 4 parity bits is

read from Memory. What was the original 8 bit word that was written in to

the memory if the 12 Bit word read out is as follows?

i) 000011101010

ii) 101110000110

iii) 101111110100

[15]

3 a) Realize the code converter which converts the binary (BCD) code into the

Hamming code as specified in table

[10]

b) Design a combinational circuit with three inputs and one output. Output is 1

when the binary Value of inputs has two high inputs otherwise 0

[5]

4 a) Explain the working of carry look ahead adder and express how it is

advantageous over 4 bit Ripple adder.

[8]

b) Construct the 4 bit parallel adder with look ahead carry generation?

[7]

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Code No: R22023

5 a) A cross-bar switch is a two-input x0, x1 two-output y0, y1device with a

control input w that realizes the mapping y0 = x0 + wx1 and y1 = x1 +

wx0. Realize the cross-bar switch by (2 × 1) multiplexers.

[7]

b) Explain with the help of logic diagram the operation of 3-to-8 line decoder?

How such decoders are used in the realization of 1:64 de-multiplexers?

[8]

6 a) Explain

i) Write and Read operation

ii) ROM and RAM

iii) Programmable Devices with Examples

iv) FPGA and CPLD

[8]

b) Implement the following Boolean functions with a PLA

i) F (x,y,z) = ∑ (0,1,2,5,6) ii) F (x,y,z) = ∑(1,3,6,7)

[7]

7 a) Distinguish between combinational and sequential logic circuits. [7]

b) Draw and explain the all operations of Universal shift register

[8]

8 a) Obtain a minimal state table using partition technique for the state table given

below. Find the minimum length sequence that distinguishes state from A

from state B.

[15]

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Correction in II B.Tech II semester Switching Theory & Logic Design (Code No:

R22023/R10 )

Set No: 1 – Question No:7(b)

7. b) What is shift register? Explain Universal shift register in detail?

code no: r22041 r10 ii b. tech ii semester supplementary ... · pdf fileii b. tech ii semester...

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