Question 1

The equivalent form of the logical expression ABC + A BC + ABC + ABC + AB C is

Accepted Answer

This can be solve by using Boolean identity but using k map it will be more easy (A + B + C) (A + B + C) (A + B + C).

Question 2

An air-filled rectangular waveguide has dimensions 8cm x 10cm . The phase velocity of guided wave at frequency of 3 GHz for TE10 mode is

Accepted Answer

∴ VP = 3.46 x 108 m/s.

Question 3

If x[n] then the sequence x[n] is

Accepted Answer

Consider Number of samples per period = 10p This is not a rational number. Hence signal is non periodic.

Question 4

The impulse response and the excitation function of a linear time invariant causal system are shown in figure (a) and (b) respectively. The output of the system at t = 2 sec is equal to

Accepted Answer

The area of the shaded region .

Question 5

Consider the following Maximum energy of electrons liberated photoelectrically is independent of light intensity Maximum energy of electrons liberated photoelectrically varies nonlinearly with frequency of incident light.

Accepted Answer

Statement (ii) is false because maximum energy of photons varies linearly with frequency of incident light. It can be shown as follows : F1 > F2 > F3 j = light intensity = constant Photocurrent Vs Anode voltage with frequency and incident light as a parameter. The light intensity is constant.

Question 6

In a flash type ADC, employing 15 comparators resolution with 10 volts reference; is expected to be :

Accepted Answer

Since number of comparators = 2n - 1 = 15; Then number of bits are '4' Resolution

Question 7

Consider the system with and where p and q are arbitrary real numbers. Which of the following statements about the controllability of the system is true?

Accepted Answer

Use the condition of controllability.

Question 8

In a 4 bit weighted resistor D/A converter, the resistor value corresponding to LSB is 32 kΩ. The resistor value corresponding to MSB will be

Accepted Answer

2n - 1 R = 32 K&Omeg; n = 4 ⇒ 8R = 32 R = 4 KΩ.

Question 9

For a = - 1, find the value of V2

Accepted Answer

V1 = i1R1 + i2R2 i1 + ai1 = i2 V2 = i2R2 Putting a = - 1 = 0 V.

Question 10

The specific gravity of tungsten is 13.8 and its atomic weight is 184.0 Assume that there are two free elements per atom. Then the Fermi level or characteristic energy for the crystal in eV will be

Accepted Answer

A quantity of any substance equal to its molecular weight in grams is a mole of that substance contains the same number of molecules as one mole of any other substance. This Avogadro's number and equals 6.02 x 1023 molecules per mole. Thus = 9.03 x 1028 electrons/m3 Since for tungsten the atomic and the molecular weights are the same. Therefore for tungsten EF = 3.64 x 10-19(η)2/3 = 3.64 x 10- 19(9.03 x 1028)2/3 EF = 7.326 eV.

Question 11

As the temperature increases the mobility of electrons __________ .

Accepted Answer

Mobility of electrons m = 2.5 for electrons and 2.7 for holes in Si.

Question 12

In the circuit below, delay of the EXOR and AND Logic gates are 20 μs and 10 μs respectively, then the wave y' and y (with initial condition y = 1) will be :

Accepted Answer

Since y is at logic '1' initially, y' must be at logic '1'. Also, one input of the EXOR gate is tied to zero therefore 'f' will be directly transferred to the output. The logic gates will introduce gate delays which will lead to the answer .

Question 13

The ratio of the diffusion coefficient in a semiconductor has the units

Accepted Answer

.

Question 14

The amplitude of a pair of composite sinusoidal signal y(n) = x1(n) + x2(n) with x1(n) = sin (5pn) x2(n) = 3 sin (5pn) is __________ .

Accepted Answer

Amplitude = .

Question 15

A TV picture is to be transmitted over a channel of 6 MHz bandwidth at a 35 dB S/N ratio. The capacity of the channel is

Accepted Answer

W = B = Bandwidth C = 6 x 106 x 12 = 72 Mbps.

Question 16

If the system T.F. is The differential equation representing the system is

Accepted Answer

(s3 + 2s2 + 5s + 6)y(s) = (s2 + 4) x (s) s3y(s) + 2s2y(s) + 5sy(s) + 6y(s) = s2 x (s) + 4 x (s) Replacing s by and y(s) by y(t) and x(s) by x(t) we get y(t) + 2y(t) + 5y(t) + 6y(t) = x(t) + 4x(t) + 2 + 5 + 6 = + 4x This is required differential equation.

Question 17

What are the values of Emax and Emin displayed on the oscilloscope, when a 1 kV P-P carries is modulated to 50%?

Accepted Answer

Emax - Emin = 0.5 x 1 kV = 0.5 kV 2Emax = 1.5 kVi, Emax = 0.75 kV Emin = 0.25 kV.

Question 18

A n-channel JFET has IDSS = 2 mA, Gate to source voltage VGS = - 2 V and trans-conductance is 0.5 mW then pinch-off voltage is __________ .

Accepted Answer

∴ ∴ = - 8VP - 16 ∴ + 8VP + 16 = 0 ∴ (VP + 4)2 = 0 ∴ VP = -4 V.

Question 19

Suppose that the modulating signal is m(t) = 2cos (2pfmt) and the carrier signal is xC(t) = AC cos(2pfct), which one of the following is a conventional AM signal without over modulation?

Accepted Answer

(C) is without over modulation.

Question 20

A MOSFET has a threshold voltage of 1 V and oxide thickness of 500 x 10-8 [εr = 3.9; ε0 = 8.85 x 10-14 F/cm, q = 1.6 x 10-19 c]. The region under the gate is ion implanted for threshold voltage tailoring. The base and type of impant required to shif…

Accepted Answer

VT(new) = VT(odd) + = 6.903 x 10-8 ∴ ∴ fB = - 8.6 x 1011 The threshold voltage is always negative for p-channel and hence implant is of p-type.

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