Placement Papers: DRDO Paper on 7th Sept 2008
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I have attended Scientist Entry Test on 7th Sep. Hereby I am submitting paper for Electronics and Communication branch. Hope it helps future aspirants.
SectionA

The current I in the given network.

1A

3A

5A

7A


For the DeltaWye transformation in given figure, the value of the resistance R is:

⅓ ohms

⅔ ohms

3/2 ohms

3 ohms


In the given network, the Thevenin's equivalent as seen by the load resistance Rl is

V = 10 V, R = 2ohms

V = 10V, R = 3 ohms

V = 15V, R = 2ohms

V = 15V, R = 3 ohms


The current I in a series RL circuit with R = 10 ohms and L = 20mH is given by i = 2sin500t A. If v is the voltage across the RL combination then i

lags v by 45 degree

is inphase with v

leads v by 45

lags v by 90


In thr given network, the mesh current I and the input impedance seen by the 50 V source, respectively, are

125/13 A and 11/8 ohms

150/13 A and 13/8 ohms

150/13 A and 11/8 ohms

125/13 A and 13/8 ohms


A voltage sourcehaving a source impedance Z = R + jX can deliver maximum Average power to a load impedance Z, when

Z = R + jX

Z = R

Z = jX

Z = R jX


In the given circuit, the switch S is closed at t = 0. Assuming that there is no initial Charge in the capacitor, the current i (t) for t>0 is

V/R e^2t/RC

V/R e^t/RC

V/2R e^2t/RC

V/2R e^t/RC


For the circuit in given figure, if e (t) is a ramp signal, the steady state value of the Output voltage v (t) is

0

LC

R/L

RC


For the series RLC circuit in given figure, if w = 1000 rad/sec, then the current I (in Amperes) is

2? 15

2? 15

v2? 15

v2? 15


The Yparameter matrix (mA/V) of the twoport given network is

[2 − 1 − 1 2]

[2 1 − 1 2]

[1 − 2 − 1 2]

[2 1 1 2]


The maximum number of trees of the given graph is

16

25

100

125


Given figure shows a graph and one of its trees. Corresponding to the tree, the group of branches that CAN NOT constitute a fundamental cut set is

1, 2, 3

1, 4, 6, 8, 3

5, 6, 8, 3

4, 6, 7, 3


The Yparameter matrix of a network is given by Y = [1 1 − 1 1] A/V. The Z11 parameter of the same network is

½ ohms

1/v2 ohms

1 ohms

2 ohms


For the given circuit, the switch was kept closed for a long time before opening it at t = 0. The voltage v (0 + ) is

10 V

1 V

0V

10 V


The input impedance of a series RLC circuit operating at frequency W = v2w, w being the resonant frequency, is

Rj (wL/v2) ohms

R + j (wL/v2) ohms

Rjv2wL ohms

Rjv2wL ohms


The threshold voltage V is negative for

an nchannel enhancement MOSFET

an nchannel depletion MOSFET

an pchannel depletion MOSFET

an pchannel JFET


At a given temperature, a semiconductor with intrinsic carrier concentration ni = 10^{16}/m^{3} is doped with a donor dopant of concentration Nd = 10^{26}/m^{3}. Temperature remaining the same, the hole concentration in the doped semiconductor is

10^{26}/m^{3}

10^{16}/m^{3}

10^{14}/m^{3}

10^{6}/m^{3}


At room temperature, the diffusion and drift constants for holes in a Ptype semiconductor were measured to be Dp = 10 cm^{2}/s and µp = 1200 cm^{2}/Vs, respectively. If the diffusion constant of electrons in an Ntype semiconductor at the same temperature is Dn = 20 cm^{2}/s, the drift constant for electrons in it is

µn = 2400 cm^{2}/Vs

µn = 1200 cm^{2}/Vs

µn = 1000 cm^{2}/Vs

µn = 600 cm^{2}/Vs


A common LED is made up of

intrinsic semiconductor

direct semiconductor

degenerate semiconductor

indirect semiconductor


When operating as a voltage regulator, the breakdown in a Zener diode occurs due to the

tunneling effect

avalanche breakdown

impact ionization

excess heating of the junction.


If the common base DC current gain of a BJT is 0.98, its common emitter DC current gain is

51

49

1

0.02


Negative resistance characteristics is exhibited by a

Zener diode

Schottky diode

photo diode

Tunnel diode


Let En and Ep, respectively, represent the effective Fermi levels for electrons and holes during current conduction in a semiconductor. For lasing to occur in a PN junction of bandgap energy 1.2 eV (EnEp), should be

greater than 1.2eV

less than 1.2eV

equal to 1.1eV

equal to 0.7eV


In a Pwell fabrication process, the substrate is

Ntype semiconductor and is used to build Pchannel MOSFET

Ptype semiconductor and is used to build Pchannel MOSFET

Ntype semiconductor and is used to build Nchannel MOSFET

Ptype semiconductor and is used to build Nchannel MOSFET


In a MOS capacitor with ntype silicon substrate, the Fermi potential = 0.41 V and the flatband voltage Vfb = 0V. The value of the threshold voltage Vt is

0.82 V

0.41 V

0.41 V

0.82
Refer given figure for question 26 and 27. Assume D1 and D2 to be ideal diodes.


Which one of the following statements is true?

Both D1 and D2 are ON

Both D1 and D2 are OFF

D1 is ON and D2 is OFF

D2 is ON and D1 is OFF


Values of Vo and I, respectively, are

2V and 1.1 mA

0V and 0 mA

2V and 0.7 mA

4V and 1.3 mA


In a BJT CASCODE pair, a

common emitter follows a common base

common base follows a common collector

common collector follows a common base

common base follows a common emitter


Inside a 741 opamp, the last functional block is a

differential amplifier

level shifter

classA power amplifier

classAB power amplifier


For the MOSFET in the given circuit, the threshold voltage Vt = 0.5V, the process parameter KP = 150 µA/V^{2} and W/L = 10. The values of Vd and Id, respectively, are

Vd = 4.5 V and Id = 1 mA

Vd = 4.5 V and Id = 0.5 mA

Vd = 4.8 V and Id = 0.4 mA

Vd = 6 V and Id = 0 mA


A negative feedback is applied to an amplifier with the feedback voltage proportional to the output current. This feedback increases the

input impedance of the amplifier

output impedance of the amplifier

distortion in the amplifier

gain of the amplifier


The early effect in a BJT is modeled by the small signal parameter

r0

r?

gm


For a given filter order, which one of the following type of filters has the least amount of ripple both in passband and stopband?

Chebyshev type I

Bessel

Chebyshev type II

Elliptic


For a practical feedback circuit to have sustained oscillation, the most appropriate value of the loop gain T is

1

1

1.02

1.02


Assume the opamps in given figure to be ideal. If the input signal vi is a sinusoid of 2V peaktopeak and with zero DC component, the output signal vo is a

sine wave

square wave

pulse train

triangular wave


In a common source amplifier, the midband voltage gain is 40 dB and the upper cutoff frequency is 150kHz. Assuming single pole approximation for the amplifier the unity gain frequency fT is

6 MHz

15 MHz

150 MHz

1.5 GHz


An opamp is ideal except for finite gain and CMRR. Given the open loop differential gain Ad = 2000, CMRR = 1000, the input to the noninverting terminal is 5.002 V and the input to the inverting terminal is 4.999 V, the output voltage of the opamp is

14 V

24 V

6 V

8 V


The opamp in the circuit in given figure has a nonzero DC offset. The steady state value of the output voltage Vo is

RC dvs (t)/dt

(1/RC)  vs (t) dt

V

+ V


For the circuit in given figure, if the value of the capacitor C is doubled, the dutycycle of the output waveform Vo

increases by a factor of 2

increases by a factor of 1.44

remains constant

decreases by a factor of 1.44


Assume the opamp in the given circuit to be ideal. The value of the output voltage Vo is

3.2 Vi

4 Vi

9 Vi

10 Vi


The complement of the Boolean expression F = (X + Y + Z) (x + Z) (X + Y) is

XYZ + XZ + YZ

XYZ + XZ + XY

XYZ + XZ + YZ

XYZ + XY


The Boolean function F (A, B, C, D) = (0, 6, 8, 13, 14)? with don't care conditions d (A, B, C, D) = (2, 4, 10)? can be simplified to

F = BD + CD + ABC

F = BD + CD + ABCD

F = ABD + CD + ABC

F = BD + CD + ABCD


The Boolean function F = AD + BD can be realized by one of the following figures

For the multiplexer in given figure, the Boolean expression for the output Y is

Which one of the following is TRUE?

Both latch and flipflop are edge triggered.

A latch is level triggered and a flipflop is edge triggered.

A latch is edge triggered and a flipflop is level triggered.

Both latch and flipflop are level triggered.


In a schottky TTL gate, the Schottky diode

increases the propagation delay

increases the power consumption

prevents saturation of the output transistor

keeps the transistor in cutoff region


For which one of the following ultraviolet light is used to erase the stored contents

PROM

EPROM

EEPROM

PLA


Which one of the following is NOT a synchronous counter

Johnson counter

Ring counter

Ripple counter

Updown counter


In 8085 microprocessor, the accumulator is a

In the register indirect addressing mode of 8085 microprocessor, data is stored

at the address contained in the register pair

in the register pair

in the accumulator

in a fixed location of the memory


The output w[n] of the system shown in given figure is

x[n]

x[n − 1]

x[n] x[n − 1]

0.5 (x[n − 1] + x[n])


Which one of the following is a periodic signal

x (t) = 2 e^{j} (t + (p/4) )

x[n] = u[n] + u[n]

x[n] =? {? [n − 4k]? [n − 1 − 4k]} where k = 8to 8

x (t) = e^ (1 + j) t


If the inputoutput relation of a system is y (t) =? x (t) dt where t = 8 to 2t

linear, timeinvariant and unstable

linear, noncausal and unstable

linear, causal and time invariant

noncausal, time invariant and unstable


Which one of the can be the magnitude of the transfer function  H (jw)  of a causal system

Consider the function H (jw) = H1 (w) + jH2 (w), where H1 (w) is an odd function and H2 (w) is an even function. The inverse Fourier transform of H (jw) is

a real and odd function

a complex function

a purely imaginary function

a purely imaginary and odd function


The laplace transform of given signal is

If X (z) is the ztransform of x[n] = (½) ^  n , the ROC of X (z) is

In a linear phase system, tg the group delay and tp the phase delay are

constant and equal to each other

tg is a constant and tp is proportional to w

a constant and tg is proportional to w

tg is proportional to w and tp is proportional to w


A signal m (t), bandlimited to a maximum frequency of 20 kHz is sampled at a frequency fs kHz to generate s (t). An ideal low pass filter having cutoff frequency 37 kHz is used to reconstruct m (t) from s (t). The maximum value of fs required to reconstruct m (t) without distortion is

20 kHz

40kHz

57 kHz

77 kHz


If the signal x (t) shown in given figure is fed to an LTI system having impulse response h (t) as shown in given figure, the value of the DC component present in the output y (t) is

1

2

3

4


The characteristic equation of an LTI system is given as s^{3} + Ks^{2} + 5s + 10. When the system is marginally stable, the value of K and the sustained oscillation frequency w, respectively, are

2 and 5

0.5 and v5

0.5 and 5

2 and v5


The time required for the response of a linear timevariant system to reach half the final value for the first time is

delay time

peak time

rise time

decay time


The signal flow graph of the given network is

Let c (t) be the unit step response of a system with transfer function K (s + a)/(s + K). If c (0 + ) = 2 and c (8) = 10, then the values of a and K, respectively, are

2 and 10

2 and 10

10 and 2

2 and10


The loop transfer function of an LTI system is G (s) H (s) = K (s + 1) (s + 5)/s (s + 2) (s + 3). For K>0, the point on the real axis that DOES NOT belong to the root locus of the system is

0.5

2.5

3.5

5.5


The state space equation of the circuit shown in given figure for x1 = v0, x2 = I is

The open loop gain of a unity feedback system is G (s) = wn^{2}/s (s + 2wn). The unit step response c (t) of the system is

If A = [2 0 0 2], then e^{At} is given by

[e^{2t} 0 0 e^{2t}]

[e^2t 0 0 e^2t]

[e^{t}/2 0 0 e^{t}/2]

[e^t/2 0 0 e^t/2]


The angles of the asymptotes of the root loci of the equation s^{3} + 5s^{2} + (K + 2) s + K = 0, for 0 ⇐ K<8, are

0 and 270

0 and 180

90 and 270

90 and 180


The bode plot corresponding to a proportional derivative controller is the one shown in given figure

In frequency modulation, the instantaneous

amplitude of the carrier signal is varied with the instantaneous amplitude of the message signal

amplitude of the carrier signal is varied with the instantaneous frequency of the message signal

frequency of the carrier signal is varied with the instantaneous amplitude of the message signal

frequency of the carrier signal is varied with the instantaneous frequency of the message signal


If X is a zero mean Gaussian random variable, then P { X ⇐ 0} is

0

0.25

0.5

1


If a singletone amplitude modulated signal at a modulation depth of 100% transmits a total power of 15W, the power in the carrier component is

5W

10W

12W

15W


In a superheterodyne receiver, rejection of the image signal can be achieved by using a

higher local oscillatorn frequency

crystal oscillator

narrow band IF filter

narrow band filter at RF stage


The number of bbits per sample of a PCM system depends upon the

sampler type

quantizer type

number of levels of the quantizer

sampling rate


Which one of the following is used for the detection of AMDSBSC signal

Ratio detector

FosterSeeley discriminator

Product demodulator

Balancedslpoe detector


Which one of the following signal pairs can represent a BPSK signal

A cos2pfct, A sinpfct

A cos2pfct, A sinpfct

A cos2pfct, A sinpfct

A sin2pfct, A cospfct


Which one of the following can be used for the detection of the noncoherent BPSK signal

matched filter

phaselocked loop

envelope detector

product demodulator


Bits of duration Tb are to be transmitted using a BPSK modulation with a carrier of frequency Fc Hz. The power spectral density of the transmitted signal has the first null at the normalized frequency

 F Fc  Tb = 0

 F Fc  Tb = 1

 F Fc  Tb = 2

 F Fc  Tb = 4


The probability of bit error of a BPSK modulation scheme, with transmitted signal energy per bit Eb, in an additive white Gaussian noise channel having onesided power spectral density N0, is

(½) erfc (Eb/2N0)

(½) erfcv (Eb/2N0)

(½) erfc (Eb/N0)

(½) erfcv (Eb/N0)


For a given transmitted pulse p (t), 0 ⇐ t ⇐ T, the impulse response of a filter matched to the received signal is

The multiple access communication scheme in which each user is allocated the full available channel spectrum for a specified duration of time is known as

GSM system uses TDMA with

If Rx (t) is the autocorrelation function of a zeromean widesense stationary random process X, then which one of the following is NOT true?

If E denotes the expectation operator, then E[XEX]^3 of a random variable X is

A discrete memoryless source produces symbols m1, m2, m3 and m4 with probabilities ½ ¼ ⅛ and ⅛ respectively. The entropy of the source is

A channel has a signaltonoise ratio of 63 and bandwidth of 1200 Hz. The maximum data rate that can be sent through the channel with arbitrary low probability of error is

For the vectors A = X ax + Y ay and B = Z az, del (A X B). is

Which one of the following relations represents Strokes'theorem (symbols have their usual meaning)?

Which one of the following relations is not correct (symbols have their usual meaning)?

The electric field component of a uniform plane wave propagating in a lossless magnetic dielectric medium is given by E (t, z) = ax 5cos (10^{9} t 20/3 z) V/m. If? 0 represents the intrinsic impedance of the free space, the corresponding magnetic field component is given by

The skin depth of a nonmagnetic conducting material at 100 MHz is 0.15 mm. The distance which a plane wave of frequency 10 GHz travels in this material before its amplitude reduces by a factor of e^1 is

A lossless transmission line has a characteristic impedance of 100 ohms and an inductance per unit length of 1 µH/m. If the line is operated at 1 GHz, the propagation constant is

When a load resistance Rl is connected to a lossless transmission line of characteristic impedance 75 ohms, it results in a VSWR of 2. The load resistance is

A twoport network characterized by the Sparameter matrix, [S] = [0.3 L0 0.9 L90 0.9 L90 0.2 L0] Is

A lossless air filled rectangular waveguide has internal dimensions of a cm * b cm. If a = 2b and the cutoff frequency of the TE02 mode is 12 GHz, the cutoff frequency of the dominant mode is

A Hertzian dipole antenna is placed at the origin of a coordinate system and it is oriented along zaxis. In which one of the following planes the radiation pattern of the antenna has a circular shape?

Which one of the following statements is not true?

The directivity of a half dipole antenna is

Which one of the following is not true for a step index optical fibre?

It can support multiple modes

HE11 mode is its lowest order mode

The refractive index of the cladding is higher than that of the core

At a given wavelength, single mode operation is possible by proper choice of core diameter, core and cladding refractive indices.

Section B

Sarnath is situated in the state of

MP

Bihar

Punjab

UP


Green house effect is due to the increase of atmospheric

CO2 level

SO2 level

CO level

N2 level


In the month of July, it is winter in

New York

Beijing

Sydney

London


The chairman of the Planning commission of India is

The prime minister

The vicepresident

The union finance minister

The union commerce minister


The satellite launch vehicle that placed a number of satellites ito orbit in May 2008 is

PSLVC7

PSLVC8

PSLVC9

PSLVC10


DRDO was formed in

1947

1950

1954

1958


SAMYUKTA is developed for the use of

Navy

Army

Air force

RAC


DARL 202 is a variety of

pea

garlic

capsicum

tomato


TRISHUL is

a surface to surface battlefield missile

a quick reaction surface to air missile

an intermediate range ballistic missile

a supersonic cruise missile


HUMSA is a

sonar

tank

mine

night vision device


The value of 1 + 2i/3 − 4i + 2 − I/5i, where i^{2} is1, is

5/2

5/2

⅖

⅖


The particular solution of the differential equation d^{2y}/dx^{2} + 2 dy/dx + 5y = 0 satisfying the conditions y (0) = 0 and y (0) = 1 is

y = ½ e^x cos2x

y = ½ e^x sin4x

y = ½ e^x sin2x

y = ½ e^x cos4x


For the vectors A = 3i − 2j + k and B = 2ik, the value of (A * B). A is

0

1

2

3


The orthogonal trajectory of the family of curves x^{2} − y^{2} = a (where a is a constant) and passing through the point (1, 1) is

y = 1/x

y = 1/x

y = x

y = x


The value of the line integral? y^{2} dx + 2xydy over the curve x = accost, y = asint is

0

1

2

4


The nth partial sum of the infinite series 1/1 * 2 + ½ * 3 + ⅓ * 4 + 1/n * (n + 1).

1/n + 1

n + 2/n + 1

n/n + 1

n − 1/n + 1


The complexvalued function f (z) = e^{z} is analytic for

no z

all z

real z only

imaginary z only


The inverse of the matrix [ cos A sin A #sin A cos A] is

Consider the function f (x) defined as F (x) = 3x − 1, x<0

Two events A and B with probability 0.5 and 0.7, respectively, have joint probability of 0.4. The probability that neither A nor B happens is

0.2

0.4

0.6

0.8


Consider the differential equation X^{2} d^{2}/dx^{2} + x dy/dx + (x^{2} − 4) y = 0. The statement which is not true for it is

It is a linear second order ordinary differential equation

It can not be reduced to a differential equation with constant coefficients

X = 0 is a regular singular point

It is a nonhomogeneous second order ordinary differential equation


The sum of two numbers is 16 and the sum of their squares is a minimum. The two numbers are

10, 6

9, 7

8, 8

5, 11


The value of the definite integral 0 (p/2)? ^ (⅓) x^{2} sin (x^{3}) dx is

⅓

0

1

⅓


A circle C2 is concentric with the circle C1: x^{2} + y^{2} − 4x + 6y − 12 = 0 and has a radius twice that of C1. The equation of the circle C2 is

x^{2} + y^{2} − 4x + 6y − 13 = 0

x^{2} + y^{2} − 4x + 6y − 87 = 0

x^{2} + y^{2} − 4x + 6y − 100 = 0

x^{2} + y^{2} − 4x + 6y − 88 = 0


Consider the quadratic equation x^{2} + px + q = 0. If p and q are roots of the equation, the values of p and q are

p = 0, q = 0 only

p = 1, q = 2 only

p = 0, q = 0 and p = 1, q = 2

p = 0, q = 0 and p = 2, q = 1


Consider the list of words: Etiquette, accommodate, forty, exaggerate, continous, independent, receipt. The number of misspelt words are

1

2

3

4


Consider the following sentences

A few friends he has are all very rich.

Do not insult the weak.

The later of the two persons was more interesting.

All the informations were correct.
Out of these sentences, the grammatically correct sentence is

1

2

3

4


The appropriate auxiliary verb to fill in the blank of the sentence Gandhi knew that he __ soon be jailed. Is

would

will

shall

may


The number of missing punctuation marks in the sentence Rajesh along with Amit went to the market. Is

0

1

2

3


The meaning of the word PLAGIARISM is

theft of public money

theft of ideas

belief in one god

belief in many gods


The antonym of the word TRANSIENT is

certain

close

permanent

fast


ACROPHOBIA is the abnormal fear of

open spaces

height

fire

water


The appropriate pair of prepositions to fill in the blank in the sentence He was angry __ me, because my remarks were aimed __ him. Is

at, to

with, at

with, to

at, for


The appropriate word (s) to fill up the blank in the sentence I remember __ voices in the middle of the night. Is (are)

hear

to hear

hearing

heard


The passive voice form of the sentence I have known him for a long time. Is

He is known to me for a long time.

He is known by me for a long time.

He has been known to me for a long time.

He has been known by me for a long time.


If kennel is to a dog, then __ is to a hen.

nest

coop

hole

stable


If NATION is to 5236765, then NOTION is to

573675

563765

576375

557365


The next two numbers of the series 3, 5, 11, 21 are

34 and 52

34 and 53

35 and 52

35 and 53


A, B and C are three places in India with longitudes 80E, 85 E and 90 E respectively. Which one of the following statements about the local times of the places is true?

Local time of C is ahead of that of B.

Local time of B is ahead of that of C.

Local time of A is ahead of that of C.

A, B and C all have the same local time.


In this question, notations +,/and * are used as follows A + B means A is the husband of B. A/B means A is the sister of B. A * B means A is the son of B. With these relations, the relationship denoted by P/Q * R is

P is son of R

P is daughter of R

P is uncle of R

P is father of R


If DELHI is written as EDHIL, then PARIS is written as

APRIS

SARIP

SAPIR

APISR


The number of prime numbers between 10 and 50 is

10

11

12

13


The odd one in the list: LAN, TCP/IP, HACKER and KILLER is

LAN

TCP/IP

KILLER

HACKER


SAW is to carpenter as SCALPEL is to

surgeon

mason

plumber

tailor
