GATE ECE 2014 Set 2
GATE ECE
1
A cascade connection of two voltage amplifiers A1 and A2 is shown in the figure. The open-loop
gain Av0, input resistance Rin, and output resistance R0 for A1 and A2 are as follows:
A1: Av0 = 10,Rin = 10 kΩ ,R0 =1 kΩ
A2 : Av0 = 5,Rin = 5 kΩ , R0 = 200 Ω
The approximate overall voltage gain $$\frac{{\mathrm V}_\mathrm{out}}{{\mathrm V}_\mathrm{in}}$$ is ______.
A1: Av0 = 10,Rin = 10 kΩ ,R0 =1 kΩ
A2 : Av0 = 5,Rin = 5 kΩ , R0 = 200 Ω
The approximate overall voltage gain $$\frac{{\mathrm V}_\mathrm{out}}{{\mathrm V}_\mathrm{in}}$$ is ______.

2
In the differential amplifier shown in the figure, the magnitudes of the common-mode and
differential-mode gains are 𝐴cm and 𝐴d, respectively. If the resistance RE is increased, then

3
The feedback topology in the amplifier circuit (the base bias circuit is not shown for simplicity) in the figure is 

4
The power spectral density of a real stationary random process X(t) is given by
$$${S_x}\left( f \right) = \left\{ {\matrix{
{{1 \over W},\left| f \right| \le W} \cr
{0,\left| f \right| > W} \cr
} } \right.$$$
The value of the expectation
$$$E\left[ {\pi X\left( t \right)X\left( {t - {1 \over {4W}}} \right)} \right]$$$
is ---------------.
5
The input to a 1-bit quantizer is a random variable X with pdf $${f_x}(x) = 2{e^{ - 2x}}\,\,for\,\,x \ge 0$$ and $${f_x}(x) = 0\,\,for\,\,x\, < \,0$$. For outputs to be of equal probability, the quantizer threshold should be _______________.
6
The capacity of band-limited additive white Gaussian noise (AWGN) channel is given by $$C = \,W\,\,{\log _2}\left( {1 + {P \over {{\sigma ^2}\,W}}} \right)$$ bits per second (bps), where W is the channel bandwidth, P is the average power received and $${{\sigma ^2}}$$ is the one-sided power spectral density of the AWGN.
For a Fixed $${{P \over {{\sigma ^2}\,}} = 1000}$$, the channel capacity (in kbps) with infinite band width $$(W \to \infty )$$ is approximately
For a Fixed $${{P \over {{\sigma ^2}\,}} = 1000}$$, the channel capacity (in kbps) with infinite band width $$(W \to \infty )$$ is approximately
7
Coherent orthogonal binary FSK modulation is used to transmit two equiprobable symbol waveforms $${s_1}\,(t)\, = \,\alpha \,\,\cos \,\,\,2\,\pi {f_1}\,t\,and\,\,{s_{2\,}}(t)\,\, = \,\alpha \,\,\cos \,\,\,2\,\pi {f_2}\,t$$, where $$\,\alpha = 4\,\,\,mV$$. Assume an AWGN channel with two-sided noise power spectral density $$\,{{{N_0}} \over 2} = 0.5\,\, \times \,{10^{ - 12}}$$ W/Hz. Using an optimal receiver and the relation $$Q(v) = {1 \over {\sqrt {2\,\pi } }}\,\int\limits_v^\infty {e{\,^{ - {u^2}/2}}} \,du$$, the bit error probability for a data rate of 500 kbps is
8
For the following system,
When X1(s) = 0 , the transfer function $$\frac{\mathrm Y\left(\mathrm s\right)}{{\mathrm X}_2\left(\mathrm s\right)}$$ is

9
The natural frequency of an undamped second-order system is 40 rad/s. If the system is
damped with a damping ratio 0.3, the damped natural frequency in rad/s is ________.
10
The Bode asymptotic magnitude plot of a minimum phase system is shown in the figure.

If the system is connected in a unity negative feedback configuration, the steady state error of the closed loop system, to a unit ramp input, is
11
An unforced linear time invariant (LTI) system is represented by
$$$\left[ {\matrix{
{\mathop {{x_1}}\limits^ \bullet } \cr
{\mathop {{x_2}}\limits^ \bullet } \cr
} } \right] = \left[ {\matrix{
{ - 1} & 0 \cr
0 & { - 2} \cr
} } \right]\left[ {\matrix{
{{x_1}} \cr
{{x_2}} \cr
} } \right].$$$
If the initial conditions are x1(0)= 1 and x2(0)=-1, the solution of the state equation is
12
Consider the state space system expressed by the signal flow diagram shown in the figure.

The corresponding system is
13
The outputs of the two flip-flops Q1, Q2 in the figure shown are initialized to 0, 0. The sequence
generated at Q1 upon application of clock signal is

14
In the circuit shown, choose the correct timing diagram of the output (y) from the given waveforms
W1, W2, W3 and W4.


15
The number of bytes required to represent the decimal number 1856357 in packed BCD
(Binary Coded Decimal) form is __________ .
16
For an n - variable Boolean function maximum number of prime implicants is
17
In a half-subtractor circuit with X and Y as inputs, the Borrow (M) and Difference (N = X - Y) are given by
18
In the transmission line shown, the impedance $${Z_{in}}$$ (in ohms) between node A and the ground is

19
To maximize power transfer, a lossless transmission line is to be matched to a resistive load impedance via a $$\lambda /4$$ transformer as shown.


20
Which one of the following field patterns represents a TEM wave traveling in the positive $$x$$ direction?
21
If the electric field of a plane wave is
$$$\overrightarrow E \left( {z,t} \right) = \widehat x3\cos \left( {\omega t - kz + {{30}^ \circ }} \right) - \widehat y4\sin \left( {\omega t - kz + {{45}^ \circ }} \right)\left( {mV/m} \right)$$$
The polarization state of the plane wave is
22
For a rectangular waveguide of internal dimensions $$a\,\, \times \,\,b$$ (a > b), the cut-off frequency for the $$T{E_{11}}$$ mode is the arithmetic mean of the cut-off frequencies for $$T{E_{10}}$$ mode and $$T{E_{20}}$$ mode. If a $$ = \sqrt 5 \,cm$$, the value of b (in cm) is
23
Assume electronic charge q = 1.6×10-19 C, kT/q = 25 mV and electron mobility μn = 1000
cm2/V-s. If the concentration gradient of electrons injected into a P-type silicon sample is
1×1021/cm4, the magnitude of electron diffusion current density (in A/cm2) is _________.
24
Consider an abrupt PN junction (at T = 300 K) shown in the figure. The depletion region width Xn
on the N-side of the junction is 0.2 µm and the permittivity of silicon (εsi) is 1.044×10-12 F/cm. At
the junction, the approximate value of the peak electric field (in kV/cm) is _________.


25
An increase in the base recombination of a BJT will increase
26
In CMOS technology, shallow P-well or N-well regions can be formed using
27
For the n-channel MOS transistor shown in the figure, the threshold voltage VTh is 0.8V. Neglect channel length modulation effects. When the drain voltage VD = 1.6 V, the drain current ID was found to be 0.5 mA.

28
For the MOSFETs shown in the figure, the threshold voltage |Vt| = 2V and
K=$${1 \over 2}\mu {C_{OX}}\left( {{W \over L}} \right) = 0.1mA/{V^2}$$ . The value of ID (in mA) is _______
K=$${1 \over 2}\mu {C_{OX}}\left( {{W \over L}} \right) = 0.1mA/{V^2}$$ . The value of ID (in mA) is _______

29
The system of linear equations $$\left( {\matrix{
2 & 1 & 3 \cr
3 & 0 & 1 \cr
1 & 2 & 5 \cr
} } \right)\left( {\matrix{
a \cr
b \cr
c \cr
} } \right) = \left( {\matrix{
5 \cr
{ - 4} \cr
{14} \cr
} } \right)$$ has
30
The determinant of matrix $$A$$ is $$5$$ and the determinant of matrix $$B$$ is $$40.$$ The determinant of matrix $$AB$$ is _______.
31
The maximum value of the determinant among all $$2 \times 2$$ real symmetric matrices with trace $$14$$ is ______.
32
For $$0 \le t < \infty ,$$ the maximum value of the function $$f\left( t \right) = {e^{ - t}} - 2{e^{ - 2t}}\,$$ occurs at
33
The value of $$\mathop {\lim }\limits_{x \to \infty } {\left( {1 + {1 \over x}} \right)^x}\,\,$$ is
34
If $$\,\overrightarrow r = x\widehat a{}_x + y\widehat a{}_y + z\widehat a{}_z\,\,\,\,$$ and $$\,\left| {\overrightarrow r } \right| = r,$$ then div $$\left( {{r^2}\nabla \left( {\ln \,r} \right)} \right) $$ = ________.
35
Let $$X$$ be a random variable which is uniformly chosen from the set of positive odd numbers less than $$100.$$ The expectation, $$E\left[ X \right],$$ is __________.
36
If the characteristic equation of the differential equation $$\,{{{d^2}y} \over {d{x^2}}} + 2\alpha {{dy} \over {dx}} + y = 0\,\,$$ has two equal roots, then the values of $$\alpha $$ are
37
The real part of an analytic function $$f(z)$$ where $$z=x+jy$$ is given by $${e^{ - y}}\cos \left( x \right).$$ The imaginary part of $$f(z)$$ is
38
For the 8085 microprocessor, the interfacing circuit to input 8-bit digital data (DI0 – DI7)
from an external device is shown in the figure. The instruction for correct data transfer is


39
Norton's theorem states that a complex network connected to a load can be replaced with an equivalent impedance
40
In the figure shown, the ideal switch has been open for a long time. If it is closed at t=0, then
the magnitude of the current (in mA) through the $$4k\Omega$$ resistor at t = 0+ is _______.


41
A series LCR circuit is operated at a frequency different from its resonant frequency. The
operating frequency is such that the current leads the supply voltage. The magnitude of
current is half the value at resonance. If the values of L, C and R are 1 H, 1 F and 1Ω ,
respectively, the operating angular frequency (in rad/s) is ________.
42
In the h-parameter model of the 2-port network given in the figure shown, the value of h22 (in
S) is _____ .


43
In the figure shown, the capacitor is initially uncharged. Which one of the following
expressions describes the current I(t) (in mA) for t > 0?


44
In the magnetically coupled circuit shown in the figure, 56 % of the total flux emanating from one coil links the other coil. The value of the mutual inductance (in H) is ______ .

45
An FIR system is described by the system function
$$$H(z) = 1 + {7 \over 2}{z^{ - 1}} + {3 \over 2}{z^{ - 2}}$$$
46
Let x$$\left[ n \right]$$ = x$$\left[- n \right]$$ . Let X(z) be the z-transform of x$$\left[ n \right]$$. if 0.5 +j 0.25 is a zero of X(z), which one of the folowing must also be a zero of X (z)
47
The input-output relationship of a causal stable LTI system is given as
𝑦[𝑛] = 𝛼 𝑦[𝑛 − 1] + $$\beta $$ x[n].
If the impulse response h[n] of this system satisfies the condition $$\sum\limits_{n = 0}^\infty h $$[n] = 2, the relationship between α and is $$\alpha $$ and $$\beta $$ is
𝑦[𝑛] = 𝛼 𝑦[𝑛 − 1] + $$\beta $$ x[n].
If the impulse response h[n] of this system satisfies the condition $$\sum\limits_{n = 0}^\infty h $$[n] = 2, the relationship between α and is $$\alpha $$ and $$\beta $$ is
48
The value of the integral $$\int\limits_{ - \infty }^\infty {\sin \,{c^2}} $$ (5t) dt is
49
Consider a discrete-time signal
$$x\left[ n \right] = \left\{ {\matrix{ {n\,\,for\,\,0 \le n \le 10} \cr {0\,\,otherwise} \cr } } \right.$$
$$x\left[ n \right] = \left\{ {\matrix{ {n\,\,for\,\,0 \le n \le 10} \cr {0\,\,otherwise} \cr } } \right.$$
If $$y\left[ n \right]$$ is the convolution of $$x\left[ n \right]$$ with itself, the value of $$y\left[ 4 \right]$$ is
50
Consider the periodic square wave in the figure shown.
The ratio of the power in the 7th harmonic to the power in the 5th harmonic for this waveform is closest in value to _______.
