AP PGECET 2016 EC Question Paper Answer Key PDF
AP PGECET 2016 EC Question Paper Answer Key PDF
AP PGECET 2016 EC Question Paper Answer Key PDF
:
A
SET EC - 16
Electronics & Communication Engineering
Duration of Test : 2 Hours Max. Marks : 120
INSTRUCTIONS
1. This Question Booklet consists of 120 multiple choice objective type questions to be answered
in 120 minutes.
2. Every question in this booklet has 4 choices marked (A), (B), (C) and (D) for its answer.
3. Each question carries one mark. There are no negative marks for wrong answers.
4. This Booklet consists of 16 pages. Any discrepancy or any defect is found, the same may be
informed to the Invigilator for replacement of Booklet.
5. Answer all the questions on the OMR Answer Sheet using Blue/Black ball point pen only.
6. Before answering the questions on the OMR Answer Sheet, please read the instructions printed
on the OMR sheet carefully.
7. OMR Answer Sheet should be handed over to the Invigilator before leaving the Examination
Hall.
8. Calculators, Pagers, Mobile Phones, etc., are not allowed into the Examination Hall.
9. No part of the Booklet should be detached under any circumstances.
10. The seal of the Booklet should be opened only after signal/bell is given.
EC-16-A
ELECTRONICS & COMMUNICATION ENGINEERING (EC)
1 1 3
1. The sum of the eigen values of the matrix A = 0 2 1 is equal to
−4 4 3
(A) 6 (B) 8 (C) 0 (D) 1
µ −1 0
2. If the rank of the matrix A = 0 2 −1 is 2 then µ =
−4 4 3
(A) 1 (B) 8 (C) 0 (D) 2/5
∂2 f ∂2 f ∂2 f
4. If r = , s = and t = , then at the saddle point the function f ( x, y ) satisfy
∂x2 ∂x∂y ∂y 2
(A) rt − s 2 = 0 (B) rt − s 2 > 0
(C) rt − s 2 < 0 (D) st − r 2 > 0
5. If f ( z ) is analytic within and on a closed curve C and a is any point within C then the
f (z) = I
1 f (z)
k z–a
.dz, where k is equal to
1 1 1
(A) (B) (C) i (D) 2π i
π 2π 2π
2 1
dy
8. The order of the differential equation + 5y3 = x is
dx
(A) 1 (B) 6 (C) 2 (D) 1/3
Set - A 2 EC
9. An integrating factor of xy′ + y = x3 y6
1
(A) x2 y6 (B) e1/ x (C) (D) x
x
11. The impulse response of an LTI system is given by 2 20. Determine the
output if the input is
.
(A) 20
(B) 2
20 (C) 2 20
(D) 2 20
12. The input output relationship of a system is given by cos . The system is
(A) linear and invertible (B) linear and non-invertible
(C) non-linear and invertible (D) non-linear and non-invertible
13. The Fourier series coefficients of a periodic signal with time period are . Find the
signal y whose Fourier series coefficients are given by 2 and time period is
⁄5.
(A) y 25 (B) y 2/5
(C) y 10 (D) y 22/5
15. The signals $ and
are both band-limited to %$ , '%$ and %
, '%
respectively. The Nyquist sampling rate for the signal $
will be
(A) 2%$ if %$ ( %
(B) 2%
if %$ ) %
*+ ,*-
(C) 2%$ ' %
(D)
16. The response of an LTI discrete-time system to a periodic input with period . is
(A) not periodic. (B) periodic having a period ..
(C) periodic having a period 2.. (D) periodic having a period ./2.
17. The step response of an LTI system whose impulse response is
(A) ' 1 (B)
(C) 1 (D)
18. If the Fourier series coefficients of a signal are periodic, then the signal must be
(A) continuous-time, periodic. (B) discrete-time, periodic.
(C) continuous-time, non-periodic. (D) discrete-time, non-periodic.
Set - A 3 EC
19. Let represent the discrete-time Fourier series (DTFS) coefficients of the periodic
sequence with period .. The DTFS coefficients of the signal 1 in terms of
are
(A) (B) " (C) , / (D) " /
- -
1*2 3
20. The Fourier transform of the exponential signal 0 is
(A) a constant (B) a rectangular pulse
(C) an impulse (D) a series of impulses
21. The frequency response of a system with 1 is given by
(A) % % 1 (B) 1 0 1*
(C) % % 1 (D) 1 0 "1*
24. In an .-point DFT of a finite duration signal of length 5, the value of . should be
(A) . 6 5 (B) . 0 (C) . ) 5 (D) . 5
25. The algorithm used to compute any set of equally spaced samples of Fourier transform on
the unit circle is
(A) DFT algorithm (B) FFT algorithm
(C) Goertzel algorithm (D) Chirp transform algorithm
27. The steady-state error of a feedback control system with an acceleration input becomes
finite in a
(A) type 0 system (B) type 1 system
(C) type 2 system (D) type 3 system
>?,@
28. Considering the root locus diagram for a system with < = , the
??,
?,A? - ,
?,
meeting point of the asymptotes on the real axis occurs at
(A) –1.2 (B) –0.85 (C) –1.05 (D) –0.75
Set - A 4 EC
B?,C
29. If for a control system, the Laplace transform of error e is given as ??,$D
then the
steady state value of the error works out as
(A) 3.6 (B) 1.8 (C) 3.2 (D) 2.4
30. The equation 2= A ' sC ' 3=
' 5= ' 10 0 has ________ roots in the left half of
s–plane.
(A) one (B) two (C) three (D) four
>
31. Given a unity feedback control system with < = ??,A , the value of F for a damping
ratio of 0.5 is
(A) 1 (B) 16 (C) 32 (D) 64
33. If the Nyquist plot of the loop transfer function <=G= of a closed-loop system encloses
the 1, H0 point in the < =G= plane, the gain margin of the system is
(A) zero (B) greater than zero
(C) less than zero (D) infinity
$"I J? $"I J?
(C) $,J?
, K ( 1, ( 0 (D) $,J?
, K ) 1, ( 0
35. A system with gain margin close to unity or a phase margin close to zero is
(A) highly stable (B) oscillatory
(C) relatively stable (D) unstable
37. If the system matrix of a linear time invariant continuous system is given by
0 1
LM N, its characteristic equation is given by
3 5
(A) =
' 5= ' 3 0 (B) =
3= 5 0
(C) =
' 3= ' 5 0 (D) =
' 2= ' 2 0
Set - A 5 EC
38. A phase lag-lead network shifts the phase of a control signal in order that the phase of the
output
(A) lags at low frequencies and leads at high frequencies relative to input
(B) leads at low frequencies and lags at high frequencies relative to input
(C) lags at all frequencies relative to input
(D) leads at all frequencies relative to input
40. The state-variable description of a linear autonomous system is PQ LP , where X is a two-
0 2
dimensional state vector and L is a matrix given by L M N. The poles of the system
2 0
are located at
(A) –2 and +2 (B) –2j and +2j
(C) –2 and –2 (D) +2 and +2
41. 24 voice channels (4 KHz bandwidth) are sampled at 8 times the Nyquist rate and
multiplexed. Each voice channel is delta modulated. 1 bit is added per frame for
transmitting control information. What is the data rate of transmission ?
(A) 1.600 Mbps (B) 1.544 Mbps
(C) 2.048 Mbps (D) 1.536 Mbps
42. The characteristic of the channel resembles the filter shown in the figure 1. Find the time
delay of the channel.
R
Figure 1
1 f f
(A) tan -1 (B) 2πf tan -1
2πf 2πRC 2πRC
1
(C) tan -1 (2πfRC) (D) 2πf tan-1 (2πfRC)
2πf
1
43. Let X be a continuous random variable with uniform PDF defined by f x ( x) = , for
2π
0 ) ) 2O and zero elsewhere. Find σ x .
π π π π
(A) (B) (C) (D)
3 6 3 6
Set - A 6 EC
44. The stationary process has
(A) ensemble average equal to time average
(B) all the statistical properties dependent on time
(C) all the statistical properties independent of time
(D) zero mean and zero variance
45. In a modulator, it is found that the amplitude spectrum of the signal at the output of the
modulator consists of a componentRS , the carrier frequency and one component each at
RS ' RT and RS RT where RT is the modulating signal frequency. The modulator used is
(A) SSB (B) PAM (C) PCM (D) AM
46. A signal 4 cos 2 ORS ' 2 cos 4 ORS ' U cos 2 ORS is applied to the system
shown in Figure 2. What will be ?
Low pass
filter
X(t) X Y(t)
2Cos2π fc t
Figure 2
(A) 4U cos 4 ORS (B) 4 cos 4 ORS
(C) 4 ' U (D) 4 U
47. The power of an FM modulated signal with modulation index V and carrier W
L cos 2 ORS is
X- X- Z-
(A)
(B)
Y1 '
[
X- Z Z-
(C)
Y1 '
[ (D) L
Y1 '
[
48. If a Gaussian process is applied to the stable linear filter, then the random process
developed at the output of the filter will be
(A) Uniform (B) Exponential
(C) Gaussian (D) Rayleigh
49. Binary data is transmitted using PSK signaling scheme with S1 (t ) = ACosωc t ,
S 2 (t ) = − ACosωc t , 0≤ t≤ Tb where bit duration Tb is equal to 0.2 ns. The carrier frequency
is f c = 5 f b . The carrier amplitude at the receiver input is 1V and the power spectral
density of the AWGN at the input is 10-11 W/Hz. The probability of error for the optimum
filter will be
(A) erfc(5.5) (B) 0.5 erfc(5) (C) 0.5erfc( 5 ) (D) erfc( 5.5 )
Set - A 7 EC
50. Which of the following is incorrect ?
(A) H ( y / x) = H ( x, y) − H ( x) (B) I ( x, y) = H ( x) − H ( y / x)
(C) H ( x, y ) = H ( x / y) + H ( y ) (D) I ( x, y) = H ( y) − H ( y / x)
\
53. The asymptotic value of ;] required to achieve the data rate equal to the channel
2
capacity when the channel bandwidth tends to infinity is equal to
(A) 1.6 dB (B) 3 dB (C) 0 dB (D) infinite
54. The golden rule for encoding messages with unequal probabilities is to
(A) Encode a message with high probability by a longer code word.
(B) Encode all messages with equal length code.
(C) Encode a message with high probability by a shorter code word.
(D) Encode a message by arbitrary choosing variable length codes.
55. The output Signal to Noise Ratio, _.`a of matched filter depends only on
(A) ratio of input noise to output noise.
(B) ratio of output noise to power spectral density of white noise at input.
(C) ratio of signal energy to power spectral density of white noise at input.
(D) correlation of input signal to output signal.
56. In _________________ multiple access is achieved by allocating different time slots for
the different users.
(A) TDMA (B) CDMA (C) FDMA (D) FGMA
58. The only one signal waveform that produces zero inter symbol interference (ISI) is
(A) sin2dD (B) cos2dD (C) sinc2dD (D) sindD
Set - A 8 EC
60. For a broad side linear array which of the following is not correct ?
(A) The maximum radiation occurs perpendicular to the line of the array at e 90a .
(B) The progressive phase shift g between elements is zero.
(C) Width of principal lobe is less than that of an end fire array.
(D) The maximum radiation occurs along the line of array at e 0a .
62. If the diameter of a h⁄2 dipole antenna is increased from h⁄100 to h⁄50 then its
(A) bandwidth increases (B) bandwidth decreases
(C) gain increases (D) gain decreases
64. An electromagnetic wave has electric field component along -direction and magnetic
field component along -direction. The electromagnetic wave is propagating along
(A) i-direction (B) -direction
(C) -direction (D) -direction
65. The lower cut-off frequency of a rectangular wave guide with inside dimensions
(3 × 4.5 cm) operating at 10 GHz is
$D $D
(A) 10 GHz (B) 9 GHz (C) j
GHz (D) C
GHz
Set - A 9 EC
69. A uniform plane wave in air is incident normally on an infinitely thick slab. If the
refractive index of the glass slab is 1.5, then the percentage of the incident power that is
reflected from the air-glass interface is
(A) 0% (B) 4% (C) 20% (D) 10%
70. In an impedance Smith chart, a clockwise movement along a constant resistance circle
gives rise to
(A) a decrease in the value of reactance
(B) an increase in the value of reactance
(C) no change in the reactance value
(D) no change in the impedance value
72. Two voltage sources, connected in parallel as shown in the below figure, must satisfy the
conditions
v1 r1
_
+
v2
_ + r2
(A) v1 ≠v2 but r1 = r2 (B) v1=v2 and r1≠r2
(C) v1=v2 and r1=r2 (D) r1≠0 or r2≠0 if v1≠v2
s 2 + 2s + 2
74. The driving point impedance function Z ( s) = can be realized
s2 + s +1
(A) R-C Network (B) R-L Network
(C) L-C Network (D) R-L-C Network
Set - A 10 EC
75. A 100Ω, 1W resistor and 800Ω, 2W resistor are connected in series. The maximum DC
voltage that can be applied continuously to the series circuit without exceeding the power
limit of any of the resistors is
(A) 90 V (B) 50 V (C) 45 V (D) 40 V
76. The Thevenin’s equivalent circuit to the left of AB in figure shown has Req is given by
(A) 1/3 Ohms (B) 3/2 Ohms (C) 1 Ohms (D) 1/2 Ohms
78. In the series RLC circuit, the power factor of the circuit at f = f L (Lower Frequency) and
f = f 0 (resonance frequency)
(A) 0.707(lag), unity (B) unity, 0
(C) 0.707(lead), unity (D) 0, unity
79. Two coils are connected in series with inductance values of 16mH and 8mH.The value of
mutual inductance is
(A) 12mH (B) 8mH (C) 2mH (D) 4mH
80. In parallel RLC circuit, if L=8H and C=2F then the value of critical resistance is
(A) 0.5 Ohms (B) 1 Ohm (C) 2 Ohms (D) 3 Ohms
81. The transient free condition in RL and RC circuits with AC excitation will not depend on
(A) Source frequency
(B) Initial phase of the excitation
(C) Maximum values of the excitation(Voltage and Current)
(D) Circuit constants(R,L, C)
82. A Unit impulse voltage is applied to one port network, which has two linear components.
If the current through the network is 0 for t<0 and decays exponentially for t>0 then the
network consists of
(A) Resistor and Inductor in series (B) Resistor and Inductor in parallel
(C) Resistor and Capacitor in parallel (D) Resistor and Capacitor in series
Set - A 11 EC
83. A graph of network has 4 nodes and 7 branches. The number of links(l), with respect to the
chosen tree, would be
(A) 2 (B) 3 (C) 4 (D) 5
84. A network consists of a large number of ideal linear resistors (R) in series with two
constant ideal sources. Power consumed by R is P1 when only the first source is active and
P2 when only the second source is active. If both sources are active simultaneously, the
power consumed by R is
(A) P1 k P2 (B) √m1 k √m2
(C) (√m1 k √m2 ) 2
(D) ( P1 k P2)2
85. Choose the logic gate family which is having minimum propagation delay
(A) TTL (B) MOS (C) DTL (D) ECL
86. An 8085 microprocessor based system uses a 4K × 8 bit RAM with a starting address of
AA00 H. The address of the last byte in this RAM is
(A) 0FFF H (B) 1000 H (C) B9FF H (D) BA00 H
87. How many memory IC’s of capacity 2K × 4 are required to construct a memory capacity
of 15K × 8 ?
(A) 14 (B) 15 (C) 16 (D) 18
88. The present output Qn of an edge triggered JK flip-flop is logic 1. If k=1 then Qn+1
(A) cannot be determined (B) will be logic ‘0’
(C) will be logic ‘1’ (D) will be race around
89. A 12-bit (3-digit) DAC that uses the BCD input code has a full scale output of 9.99 V. The
value of Vout for an input of 0110 1001 0101 is
(A) 4.11 V (B) 6.95 V (C) 7.38 V (D) 7.88 V
Set - A 12 EC
92. What is the maximum frequency with which a 4-bit binary ripple counter can work, if the
propagation delay from CLK to Q of each flip-flop is 24 ns?
(A) 100 MHz (B) 96 MHz
(C) 10.4 MHz (D) 6.9 MHz
94. The initial sequence of 4-bit Johnson counter is 1110, what will be the sequence after third
clock pulse
(A) 1000 (B) 0001 (C) 1110 (D) 0011
95. The logic function (A+B)(A′ +B′) can be implemented by giving the inputs A and B to a
two input
(A) NOR gate (B) NAND gate
(C) EX-NOR gate (D) EX-OR gate
96. The function f(A,B,C,D) = ∑m(0,1,4,6,7,8,10,14,15), the number of prime implicants and
essential prime implicants are
(A) 6, 1 (B) 6, 2 (C) 7, 1 (D) 7, 2
97. A 4.6 V is given as input to the counter type ADC and SAR type ADC then the digital
output produced respectively
(A) 0100, 0100 (B) 0101, 0101
(C) 0100, 0101 (D) 0101, 0100
99. Which of the following fabrication is suitable for maintaining the PN junction area to the
required accuracy?
(A) Grown junction type (B) Alloying
(C) Diffusion (D) Ion-implantation
Set - A 13 EC
102. Two 10 V identical zener diodes are connected back to back, the maximum voltage drop
across the diodes when they are conducting is
(A) 20 V (B) 10 V (C) 10.6 V (D) 9.4 V
103. A PN junction exhibits a transition capacitive effect of several ______ farads in reverse
bias, but may have many _____ farads of diffusion capacitance in the forward biased state.
(A) micro, pico (B) pico, micro (C) milli, milli (D) milli, micro
105. Class-A power amplifier delivers 10W to a load with input signal power of 200mW. The
power gain is
(A) 200 (B) 10 (C) 50 (D) 20
109. The current density of electrons through any conductor carrying current is given by
ne2τ neτ ne 2τ n 2 eτ
(A) j0= E (B) j 0= E (C) j 0= (D) j 0= E
m m mE m
110. In BJT, Sensitivity of β (common emitter current gain) with respect to α (common base
current gain) is
1 1
(A) (B) 1 + β (C) (D) 1
1+ β 1+α
111. A differential amplifier has a differential gain of 20000 and CMRR = 80dB. Common
mode gain is
(A) 2 (B) 1 (C) 0.5 (D) 0
Set - A 14 EC
112. Which of the following h-parameters relations is incorrect ?
(A) hic = hie (B) hrc = 1 – hre
(C) h fc = 1 + h fe (D) hoc = hoe
114. If 10 V is the peak voltage across the secondary of the transformer in a half wave rectifier
with capacitive filter, peak inverse voltage of the diode will be
(A) 20 V (B) 14.14 V (C) 10 V (D)7.8 V
115. The condition of sustained oscillation in BJT phase shift oscillator is given by
R
(where K = c and Rc is collector resistance)
R
j
C
(A) hfe> 23+ > +4K (B) hfe> 29+ > +4K
A A
(C) hfe> 23+ > +29K (D) hfe> 29+ > +23K
116. A CE amplifier has RL =1000 Ω and Re = 100 Ω and h fe =99, hie =1000 Ω; the input
resistance Ri is given approximately by
(A) 100 Ω (B) 10 KΩ (C) 1000 Ω (D) 11 K Ω
117. When an electron moves through a potential difference of 10 V, the energy acquired by it
will be
(A) 10 joules (B) 16 × 10 −19 eV
(C) 1.6× 10 −19 eV (D) 10 eV
120. The scaling factor of an MOS device is α using constant voltage scaling model, the gate
area of the device will be scaled by
(A) 1/α (B) 1/ α2 (C) 1/ α3 (D) 1/ α4
________________
Set - A 15 EC
SPACE FOR ROUGH WORK
Set - A 16 EC
Electronics and Communication Engineering (EC)
SET-A