IES Electronics Telecommunication Conventional Paper 2014

8/10/2019 IES Electronics Telecommunication Conventional Paper 2014

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09475

: : A . i > , i ~ ; r 1 A i l o t l 2 0 1 1 J r . a

I

-DMHH-N-FUA

I

ELECTRONICS AND TELECOMMUNICATION

ENGINEERING

Paper

{CONVENTIONAL .

Time Allowed : Three Hours Maximum Marks : 200

INSTRUCTIONS

Please read each of

the

following instructions carefully

before

aUempting questions

:

Candidates should attempt FNE questions in all.

Question no 1 is compulsory.

Out

of

the remaining

SIX

questions attempt any FOUR questions.

ll questions. carry equal marks. The number of marks carried by

a

part of

a question is indicated against it.

Answers must be written in

ENGLISH

only.

ssume suitable data

i f

necessary

and

indicate the same clearly.

Unless otherwise mentioned symbols

and notations have their

usual standard meanings.

Values of the following constants

may

be used as indicated;

wherever necessary :

Electronic

charge=-

16 x 10-

19

coulomb

Free space permeability = 47t x 10-

7

Henry/m

Free space permittivity= 1/367t) x 10-

9

Farad/m

Velocity oflight in free space= 3 x 10

8

m/s

Boltzmann constant = 138

X

10-

23

J/K

Planck constant = 6626 x

10--34 J-s

Neat sketches

may

be drawn wherever required.

ll parts and sub-parts

of

a question are to be attempted together

in

the answer book.

ttempts

of

questions shall

be

counted

in

chronological order.

Unless struck off attempt

of

a question shall be counted even

i f

attempted partly.

ny page or portion of the page left blank

in

the answer book

must be clearly struck off.

A-DMHH-N-FUA 1

[Contd.]

www.examrace.co


2/24

1

. A

ns

w er

ll

ofth

e fo

llow

ing

:

a)

C lea

rly

dist

ing

u ish

bet

w ee

n th

e fo

llow

ing

:

i

) C

ond

uct

ivity

a

nd M

obil

ity

i i)

Ze

ner

brea

kdo

w n

and

A va

lanc

he

brea

kdo

w n

iii)

P

iezo

ele

ctr ic

and

Ce

ram

ic

iv)

D

irec

t ba

nd-g

ap

an

dInd i

rec t

ban

d-g

ap

v)

P

olar

izab

ility

a

nd P e

rm

ittiv

ity

b) T he n-channel MO SFET in the circu it

has

VTN

=

1 V

a

nd K=

0

8 m

V

2

V

nn

=9V

Rn

=2K

i)

A

ssum

e th

at

F

E T .

is

ope

ra ti

ng

in

its

sa

tura

tion

re gi

on.

Sho

w th

at

In

:: . 1

rn

A.

ii )

D e

te rm

ine

the

tra

nsco

ndu

cta

nce

g

m.

iii)

I

fV

i =1

0 m

V

wh

at a

re d

rain

cu

rren

t an

d

v

olt

age

s?

A

-DM

HH

-N-F

UA

2

[C

ontd

.

www.examrace.co


3/24

c)

Prove

that fo r an allo

y p - n ju

nction (wi

th

NA Nnl .

the

wid

th of

the

depl

etion layer

is

give

n

by

,

.

2Jl

v

J2

=

P

J

.

r

p

where

vj

is

th

e ju

nc tion pote

ntial under

the.

co

ndition of a

pplied diod

e voltage.

(d) W

hat is a posit

ive

r

eal fun

ction as ap

plied to

driving po

in t immitta

nce function

s

?

Realize

thefollowing

d riving p

oint imped

ance

function using Foster-

form :

Z(s)

6(s + 3) s

+ 9)

s s +6)

(e)

For an LTI

system w

ith

un

it im

pulse respo

nse

h(t) e-2

t u(t), det

e rm ine the

output for

an

in

put o f x

(t) e-t u(t)

.

f) D

raw sampl

e and hold

c ircuit and

explain its

o

peration.

g) For

a transmiss

ion line, the

pr imary

constants

are:

R= 05 0/m

L

00

2 JlH/m

C lOOpF

/m

G

OOl U/m

C

om pute the

values o

f complex

propagation

co

nstant.

(h ) What

is a strain

gauge ?

W here doe

s it find

application

s

?

H

ow is

temperat

ure

compensatio

ndone in s

uch gauges

?

A-DMHH-N

-FUA

3

[Contd.]

www.examrace.co


4/24

2. (a) The following data is obtained for a nickel-iron

H A/m)

alloy during

the

generation of

steady state

ferromagnetic

hysteresis

loop :

50 25 0

10 15 20 25

50

B(Wb/m

2

)

095 094 092 090 075 055 087

095

(i)

What

is

remanent

induction ?

(ii)

What

is coercive field ?

(iii) Determine

the saturation

induction.

(iv)

Determine the saturation

magnetization.

(v) Identify

these

parameters

on

the

graph.

1

(b) (i) Why do we classify Magnesium and

Aluminium as good electrical conductors

even though outer 3s energy bands

are

filled?

(ii) How

do

you explain for poor conductivity

of

pure

diamond

with

the help of energy

band model?

1

(c)

In an

electronic watch,

the quartz

crystals

are

1 rom thick. They

are

excited piezoelectrically

in their

fundamental

mode.

(i)

Estimate

the frequency at which

they

oscillate.

(ii) Estimate its daily

drift

(sec/day) in winter

if

there is

no compensation for changes

in

the quartz. o

you think that the watch

does have such compensation ?

B

=

10

12

erg/cm3

and

p

=

27 glcm3.

1

A-DMHH-N-FUA

4

(Contd.)

www.examrace.co


5/24

(d) A steady-state magnetic field of 10 im is

incident on an iron air boundary as shown

in

figure.

IJ.r; 8000

(i)

(ii)

(iii)

a

air

l r ;

8000

H

Write

the

boundary conditions for the

magnetic field

in

terms of

the

indicated

variables

and parameters assuming

surface currents to be absent.

7t

Plot a vs 0 for

the

range 0

< a< 2 .

For

e ; : ,

find

the

magnetic flux density

m magnitude and direction at the

interface.

3. (a) A small

number

of readily ionized donors

Nn

are

added to

an

intrinsic semiconductor, such

that

0

ni where

ni

is the intrinsic carrier

concentration. Find

the

free electron and hole

concentration n a semiconductor, accurate to

1

the first order Nn

/n;

A-DMHH-N-FUA

5

[Contd.]

www.examrace.co


6/24

b)

Two identic

al

si

li on ju

nction diod

es D

1

and

D

2

.

are con

nected back

to back

as shown belo

w. The

rev

erse curren

t I

8

of each

diode is. 10 8 A

and

thebreakdownvoltage

VB

is 50

V.

Findthe

V

n

1

a

nd

Vn

2

volta

ges droppe

d across dio

des

D

1

an

d

D 2. A s s ; e ~

=2

5mv

1

D2

5V

c)

An n

-type silic

on bar is

doped unifo

rmly by

phosp

horus ato

ms to a

concentra

tion of

4

5

x

1Q15fcc.

The ba

r has a cro

ss-section

of

1 mm

2 anda

length of 1

0

em

It i,s

i l luminated

un

ifonnly for

region x

0 as sho

wn in

the

figure. Assu

me optic

al genera

tion

rate

102

1

elec

tron-hole p

airs per cm

3

/sec. The

hole

li fe

time and el

ectron lifet

ime are equ

al and a re

1

JlSec.

F

ind

the

h

ole and. el

ectron diffu

sion

cu rre

n t

at

x = 3

46

J.l

m.

Light

/

~

n-type

semicon

ductor

x

O

10

cm

x=

O

A-O

MHH-N-FUA

6

[Contd

]

\

www.examrace.co


7/24

(d)

Design

a self b

iasing circ

uit such that

le

=5mA

Vee=8

V VE=6V

8=

10

hre

=

2

and Vee=2 V

Vee

(e) A

nn channe

l MOSFE

T- T hav in

g a V of 2

V

(Threshold

voltage) is

used in

the circuit

s

shown. I

nitially T

is OF F

and is in

steady-state

. At

tim e

t

= 0,

a st

ep voltage

o f

m agn

itude

4 V

is applied to

the input s that

M OS

FET t

urns ON ins

tantaneous

ly. The

device para

meters re

K=5m

A/V

2

R

ns==

C n

s=O

Cna=O

T

1

k.Q

+o

I

v

-r-

1

v n

lOOpF

ov

D raw

the equi

valent circu

it a

nd

calc

ulate the

t ime take

n for the ou

tput

to

fall to

5 V.

A DMHH N

FUA

7

[Contd.]

www.examrace.co


8/24

4.

(a)

What

is a Ztransform? Give its utility.

(b) Obtain the Inverse - Laplace transform of

the

following:

Y s)=

s

s(s

2

+3s+2)

c)

(i)

For

the

channel and message

probabilities given

in

the

figure below,

determine

the

best

decisions about

the

transmitted

message for each possible

received response.

(ii) .

With decisions made as m

part

(a),

calculate

the

probability of error.

Ml)

P(M

1

= 05 oE---*-ll.- --3>0rl

M2)

P(M

2)

=

02

r : # 2 : . : : : : : _ - : : - = - : , . . ; : _ : _ _ _ _ _ : _ ~ r 2

(d) 40 of

the

population of a town

are

voterS, 50

are educated and 20 are educated-voters. A

person is chosen at random.

i) f he is educated,

what

is

the

probability

that he

is a voter ?

(ii)

If he

is a voter,

what

is

the

probability

that

he

is not educated ?

(iii) What is the probability that

he

is neither

4

1

1

a voter nor

educated? 1

(e) Find

the

inverse 'Fourier transform' of signum

function sgn.

6

A-DMHH-N-FUA

8

[Contd.

www.examrace.co


9/24

5

.

a) I

n

t

he

netw

ork

show

n belo

w,

the sw

itch

is

clos

ed at.

t 0

. Obta

in t

he curr

ent i

2

t) in th

e

net

w ork

fo r t

0.

102

1H

lH

~

lO

OV

1

1

b)

Find

the sh

ort c

ircuit

adm

ittanc

e pa

rame

ters

for

two p

ort n

etw or

ks as

show

n in f

ig ure

w i th

1

1

R

Ra Rb

= 1

0

and

C 1 C 2

=c=

1

Q

4

2

1

Documents

IES Electronics Telecommunication Conventional Paper 2014