PAPER-II
ELECTRONIC SCIENCE







ELECTRONIC SCIENCE Paper II Note This paper contains fifty objective type questions of two marks each. All questions are compulsory.
1. In JFET the transconductance can be expressed as
...

...

I

V

2
dss
V
gs


1

V

p p
...

...

2I

V

dss gs


1

V

V

p p
...

...

2I

V

2
dss gs


1

V

V

p p
...

...

2I

V

dss gs


1

V

V

p p
2. An electrodynamic generator is used to convert

Motion into voltage Voltage into motion


Temperature into pressure Pressure into temperature


3. The effect of adding poles and zeros can be determined for determining phase and gain margin by

Magnitude Vs phase plot Nyquist plot


Nicholas plot Bode plot


4. The small signal model of a tunnel diode in negative resistance region is











5. The logic function implemented by the circuit below is



Y=P.Q P+Q


Y=P . Q P . Q

6. For the following circuit, for making the output high the input combination must be


A=0,B=0and C=1


A=1,B=1and C=0


C=0


A=0,B=1and C=1


7. Number of times the instruction sequence below will loop before coming out of loop is MOV AL, 00H A1 INC AL JNZ A1

256 255


01 00


8. The number of wait states required to interface 8279 to 8086 with 8 MHz clock are

One Two


Three None


9. Which combination of the integer variables y and z makes the variable to get the value 4
in the following expression?
x


x x z 5


x x z 2


10. Consider the following program main(
float a 0.3, 0.5
0.6)
if 0.3) printf ("xyz"
else printf
else printf


The output is


XYZ MLN


ABC None of these


11. For a matched junction, scattering parameters are given values, which one of the following is true
S. 0
11 21
S. 0 S=1
22 21
12. The number of bits per sample in a PCM system is increased from 8 to 16. The bandwidth of the system would increase

8 times 2 times


½ times 24 times


13. An infrared LED is optically coupled to a photodiode. When LED is turned off, the reading on an ammeter in series with the reversed-biased photodiode will

Not change Decrease


Increase Fluctuate


14. After firing a SCR, the gating pulse is removed, the current in the SCR will

remains the same immediately falls to zero


rise up rise a little and then falls to zero


15. A signal is defined as at)e -at. Its Laplace transform will be
1 s

a)2 a)2


a)2
16. For intrinsic semiconductor the conductivity is
q(nµ+pµ)
n pinp

p q

npnp
Out of these the following is correct



and are correct and are correct


and are correct and are correct


17. Read the following statements

The gain crossover is a point on the plot at which the magnitude of is equal to 1.


The gain crossover is a point on the plot at which the magnitude of is equal to 0.


The gain crossover frequency, is the frequency of where 1


The gain crossover frequency is the frequency of where 0 Which of the above statements are correct


and and


and and


18. In a p-n junction diode if A is the area of a junction then the transition capacitance is
...
W2
q N q NA
a a
dW
dV

...

q NWA q NA
a a


2e
s
...

dW

dV

...

Out of these which one is correct and are correct is correct, but is wrong is correct but is wrong and are correct
J-88-16 5 Paper-II

19. In a resistive ladder network used in n bit D to A converters, the following statements are
given
1


LSB weight


(2n
1


LSB weight

(2n


The sum of all weights is equal to 1


The sum of all the weight is greater than 1
Out of the above statements following is true



and and


and and


20. The 8085 µp enters into bus idle machine cycle whenever

INTR interrupt is recognized


RST X.5 is recognized


When content of register B is 00h


DAD rp instruction is executed


Options

and are correct and are correct


and are correct and are correct


21. If x is an one-dimensional array then

x is same as x 1


is same as x


is same as x


is same as



Options

and are correct and are correct


and are correct and are correct


22. For transmission lines following statements are given

There is no cut-off frequency for TEM in coaxial cables.


Coaxial cables are useful upto 100 MHz only.


Waveguides do not support TEM waves.


All the frequencies above cut-off flow through waveguides.
Out of the above statements following is true



and and


and and


23. Which of the following statements are true for Delta modulation

The Modulation is digital in nature.


The modulation is analogue in nature.


Better signal to Noise-ratio than PCM.


Slope overload occurs in Delta Modulation.



Options

and are correct and are correct


and are correct and are correct


24. Which of the below mentioned statements are correct with respect of semiconductor LASER

pn-junctions can be formed by using direct bandgap semiconductors.


Emitted radiations should be monochromatic and coherent.


Emitted radiations be monochromatic and all are in same phase.


Emitted radiations should be monochromatic and spontaneous.



Options

are correct are correct


are correct are correct


25. Consider a two port network shown in the following figure

The z-parameters zand zfor this network are given as
11 21
6


O

11
16



z21 O

11
6



z11 O

11
16



O

11 Which of the above are correct


and and


and and

d.
A Lead-Lag Network iv.



26. Match the following lists
List I List II
a. Darlington transistor i. ß 1
b. Common base ii. ß
c. Common emitter iii. a
d. Common collector iv. ß1ß2
Codes
a b c d
iv iii ii i
i ii iii iv
iii i ii iv
ii iv i iii
27. Match the following lists
List I List II

a. A-bridge T filter i.
b. A Lead Network ii.
c. A Lag Network iii.


Codes
a b c d
ii ii i i i i iii ii iv iii ii iv iii iv iv iii
Paper-II 8 J-88-16

28. Match the following lists List- I List- II
a. hi. i/i
ie cb
b. h ii. ./i
re bb
c. hiii. ./.
fe bc
d. h iv. i/.
oe cc

Codes
ab cd

ii iii iiv


iii ii i iv


ii iii iv i


i ii iii iv


29. Match the following lists List- I List- II
a.
IC 7408 i. BCD to decimal decoder

b.
IC 7442 ii. BCD to seven segment decoder-drivers

c.
IC 7447 iii. Quad 2-input NAND gate

d.
IC 7400 iv. Quad 2-input AND gate



Codes
ab cd

i iii iv ii


ii i iv iii


iv i iii ii


iv i ii iii


30. Match the following
List I List II
a. RST 7.5 i. Non maskable interrupt
b. RST 0-7 ii. Level triggering interrupt
c. TRAP iii. Hardware interrupt
d. RST 5.5 and RST 6.5 iv. Software interrupt
Codes
a b c d
i iii ii iv
ii iii i iv
iii i ii iv
iii iv i ii
31. Match the following
List I List II
a. The program fragment i. Prints 4
int a b
printf
b. The program fragment ii. Prints 0
int a b
printf
c. The program fragment iii. Prints 1
int a b
printf("%d",
d. The program fragment iv. Prints 2
int a b
printf
Codes
a b c d
i ii iv iii
ii iii i iv
ii iii iv i
iii ii i iv
Paper-II 10 J-88-16

32. Match the following lists List- I List- II
a.
PIN diode i. Optical detector

b.
APD ii. Tuning

c.
Varacter diode iii. Microwave oscillator

d.
Tunnel diode iv. Microwave detector



Codes
ab cd

iv i ii iii


iii i ii iv


i iii ii iv


i iv ii iii


33. Match the following lists
List I List II
a. Quantization noise in i. Number of quantization levels
PCM
b. Bandwidth in PCM ii. Lesser number of quantization levels
needed
c. Sampling rate iii. Highest frequency in the analog signal
d. Differential PCM iv. Atleast twice the maximum frequency
component present in the signal
Codes
a b c d
i iii iv ii
i ii iii iv
i iv iii ii
ii iv i iii
J-88-16 11 Paper-II

34. Match the following lists
List I List II
Medium Index of refraction(.

a. Glass Fibre i. 1.0003
b. Water ii. 3.4
c. Air iii. 1.5 1.9
d. Silicon iv. 1.33
Codes
a b c d
iv iii i ii
ii iv i iii
ii i iii iv
iii iv i ii
35. Match the following lists
List I List II
a. i. z
1 z-1 z 1
b. anU[n] ii. z z a z a
c. nanU[n] iii. z 1)2 z 1
d. iv. az a)2 z a
Codes
a b c d
iii ii iv i
ii iv i iii
i ii iii iv
ii iii iv i

Directions Question No. 36 to 45
The following items consist of two statements, one labelled as "Assertion and the other labelled as the "Reason You are to examine the two statements carefully and decide if the Assertion and the Reason are individually true and if so whether the reason is a correct explanation of the assertion. Select your answer to these items using the codes given below and mark your answer accordingly.

Codes

Both and are true and is the correct explanation of


Both and are true, but is not the correct explanation of


is true, but is false.


is false, but is true.


36.
Assertion GaAs shows very low reverse saturation current, excellent temperature sensitivities and high breakdown voltages.

Reason It operates at only low frequencies as compared to Ge and Si. It has a knee voltage of 2.0 Volts.

37.
Assertion It is said that Kirchhoff's current law has never been found to be invalid. Reason The current law is based on the principle of conservation of charge.

38.
Assertion Networks that are quite stable and relatively insensitive to temperature variations have low stability factors.


Reason The stability factors are defined as
. I

CO
S(ICO)
. I
C
. V
BE
S(VBE)
. I
C
.ß

. I
C
Where . signifies the change in the quantity.
39.
Assertion In Electromagnetics, materials are divided roughly into two classes, i.e. conductors and dielectrics or insulators.

Reason In Maxwell equation, s/.. decides, whether the medium is a good conductor or a dielectric.

40.
Assertion Ready pin of 8086 microprocessor is used to introduce wait states.

Reason Because the WR and ALE signals are not available directly from the processor in maximum mode.

41.
Assertion When a static variable is defined inside a function in then it remains alive until end of the function.

Reason Because that variable is treated as local variable.

42.
Assertion In tristate buffer, at the input of a digital system, there may be more than one input signal.

Reason The tristate buffer is controlled by gate signal, when G is high, the output follows the input. However, when the signal at G is low, the output is an open circuit third state).

43.
Assertion The Fourier transform provides a unified solution for both periodic and non-periodic waveforms over the entire interval.

Reason The Fourier transform is a tool for generalized analysis of arbitrary waveforms over the entire interval.

44.
Assertion Optical communications has certain inherent advantages over conventional communications systems such as copper cable and radio links etc.

Reason It is because optical fibres have light weight and smaller diameter.

45.
Assertion Capacitive transducers are preferred over inductive transducers.


Reason Push-pull inductive transducers can be replaced with push-pull capacitive transducers.
Directions (46 50) Read the passage and answer the following questions numbering from 46 to 50 The metal oxide semiconductor field effect transistor is the most important device for very large scale integrated circuits such as microprocessor and semiconductor memories. MOSFET is also becoming a power device. The principle of field effect transistor was first proposed by Dillen Field in 1930. The current in a MOSFET is transported by carriers of one polarity and is usually referred as unipolar device. The MOSFET is a member of the family of field effect transistors. It is fabricated with various semiconductors such as Si, GaAs and SiC with various insulators. The most important system is Si SiO2
interface.
46. MOSFET is in equilibrium condition when
V 0 V .
gs ds gs ds
V . V. 0 V
gs ds gs ds
47. The cut off frequency of a MOSFET can be defined as gg
m m

2p 2p C
gs
gg

m d

g 2p C
d gs
48.
The surface charge per unit area after strong inversion is given by

49.
The threshold voltage of a MOSFET is 2e s q NA(2.B)



2.B 2.B+ C

i
2e q
2e q
sAB sAB
2.B- 2.B+
C C
i i
50. The transconductance in linear region is zz

µCV (2)
niD niG Tzz
L L


µC
nGT ni
L L
Space For Rough Work