# EC GATE 2008 (Test 4)

Tag: ec gate 2008
Q.1
For the circuit shown in the following, IIare inputs to the 4:1 multiplexers, R(MSB) and S are control bits.
The output Z can be represented by

A.
B.
C.
D.
Explaination / Solution:

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Q.2
Group I gives two possible choices for the impedance Z in the diagram. The circuit elements in Z satisfy the conditions R2C2 > R1C1. The transfer functions V0/V1 represents a kind of controller.

Match the impedances in Group I with the type of controllers in Group II
Group I                                                              Group II

A. Q - 1,R - 2
B. Q - 1,R - 3
C. Q - 2,R - 3
D. Q - 3,R - 2
Explaination / Solution:

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Q.3
Which of the following is NOT associated with a p - n junction ?
A. Junction Capacitance
B. Charge Storage Capacitance
C. Depletion Capacitance
D. Channel Length Modulations
Explaination / Solution:

Channel length modulation is not associated with a p - n junction. It is being associated with MOSFET in which effective channel length decreases, producing the phenomenon called channel length modulation.

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Q.4
For the circuit shown in the following figure, transistor M1 and M2 are identical NMOS transistors. Assume the M2 is in saturation and the output is unloaded.

The current Ix is related to Ibias as

A.
B.
C.
D.
Explaination / Solution:

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Q.5
Silicon is doped with boron to a concentration of 4 × 1017 atoms cm3. Assume the intrinsic carrier concentration of silicon to be 1.5 × 1010/cmand the value of kT/q to be 25 mV at 300 K. Compared to undopped silicon, the fermi level of doped silicon
A. goes down by 0.31 eV
B. goes up by 0.13 eV
C. goes down by 0.427 eV
D. goes up by 0.427 eV
Explaination / Solution:

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Q.6
The driving point impedance of the following network is given by

The component values are
A. L = 5H, R = 0.5Ω, C = 0.1F
B. L = 0.1H, R = 0.5Ω, C = 5F
C. L = 5H, R = 2Ω, C = 0.1F
D. L = 0.1H, R = 2Ω, C = 5F
Explaination / Solution:

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Q.7
One end of a loss-less transmission line having the characteristic impedance of 75Ω and length of 1 cm is short-circuited. At 3 GHz, the input impedance at the other end of transmission line is
A. 0
B. Resistive
C. Capacitive
D. Inductive
Explaination / Solution:

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Q.8
Four messages band limited to W,W,2W and 3W respectively are to be multiplexed using Time Division Multiplexing (TDM). The minimum bandwidth required for transmission of this TDM signal is
A. W
B. 3W
C. 6W
D. 7W
Explaination / Solution:

Bandwidth of TDM is = 1/2 (sum of Nyquist Rate) = 1/2 [2W + 2W + 4W + 6W] = 7W

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Q.9
In the following network, the switch is closed at t = 0- and the sampling starts from t = 0. The sampling frequency is 10 Hz.

The expression and the region of convergence of the z -transform of the sampled signal are
A.
B.
C.
D.
Explaination / Solution:

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Q.10
A speed signal, band limited to 4 kHz and peak voltage varying between +5 V and -5 V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. Assuming the signal to be uniformly distributed between its peak to peak value, the signal to noise ratio at the quantizer output is
A. 16 dB
B. 32 dB
C. 48 dB
D. 4 kHz