# EC GATE 2010 (Test 4)

Tag: ec gate 2010
Q.1
Choose the most appropriate word from the options given below to complete the following sentence: His rather casual remarks on politics ___ his lack of seriousness about the subject
B. belled
C. betrayed
D. suppressed
Explaination / Solution:

Betrayed means reveal unintentionally that is most appropriate.

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Topic: Arithmetic Tag: EC GATE 2010
Q.2
Given digits 2, 2, 3, 3, 4, 4, 4 how many distinct 4 digit numbers greater than 3000 can be formed
A. 50
B. 51
C. 52
D. 54
Explaination / Solution:
No Explaination.

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Q.3
Assuming that the flip-flop are in reset condition initially, the count sequence observed at QA, in the circuit shown is A. 0010111...
B. 0001011...
C. 0101111...
D. 0110100....
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Q.4
At room temperature, a possible value for the mobility of electrons in the inversion layer of a silicon n-channel MOSFET is
A.

450 cm2/V-s

B. 1359 cm2/V-s
C. 1800 cm2/V-s
D. 3600 cm2/V-s
Explaination / Solution:

At room temperature mobility of electrons for Si sample is given μn = 1350 cm2/V-s For an n-channel MOSFET to create an inversion layer of electrons, a large positive gate voltage is to be applied. Therefore, induced electric field increases and mobility decreases.
So, Mobility μn <1350 cm2/V-s for n-channel MOSFET

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Q.5
In a uniformly doped BJT, assume that NENB and NC are the emitter, base and collector doping in atoms/cm3, respectively. If the emitter injection efficiency of the BJT is close unity, which one of the following condition is TRUE
A. NE  = NB = NC
B. NE  >> NB and NB > NC
C. N = NB and NB < NC
D. N < NB < NC
Explaination / Solution:

Emitter injection efficiency is given as Workspace
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Q.6
If the scattering matrix [S ] of a two port network is then the network is
A. lossless and reciprocal
B. lossless but not reciprocal
C. not lossless but reciprocal
D. neither lossless nor reciprocal
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Q.7
Consider a baseband binary PAM receiver shown below. The additive channel noise n(t) is with power spectral density The lowpass filter is ideal with unity gain and cut-off frequency 1 MHz. Let Yk represent the random variable y(tk).
Yk = Nk , if transmitted bit bk = 0
Yk = a + Nk if transmitted bit bk = 1
Where Nk represents the noise sample value. The noise sample has a probability density function, (This has mean zero and variance 2/α2). Assume transmitted bits to be equiprobable and threshold z is set to a/2 = 10-6 V. The value of the parameter α (in V-1) is
A. 1010
B. 107
C. 1. 414 × 10-10
D. × 10-20
Explaination / Solution:

Let response of LPF filters Noise variance (power) is given as Workspace
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Q.8
The residues of a complex function at its poles are
A. 1/2, -1/2 and 1
B. 1/2, -1/2 and -1
C. 1/2, -1 and 3/2
D. 1/2, -1 and 3/2
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Q.9
Two discrete time system with impulse response h1[n] = 𝛿[n - 1] and h2[n] = 𝛿[n - 2] are connected in cascade. The overall impulse response of the cascaded system is
A. 𝛿[n - 1] + 𝛿[n - 2]
B. 𝛿[n - 4]
C. 𝛿[n - 3]
D. 𝛿[n - 1]𝛿[n - 2]
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Q.10
The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T = 300 K electronic charge = 1.6 × 10-19 C, thermal voltage = 26 mV and electron mobility = 1350 cm2 / V-s The magnitude of the electric field at x = 0.5 μm is
A. 1 kV/cm
B. 5 kV/cm
C. 10 kV/cm
D. 26 kV/cm