Exam Questions Papers MCQ Questions & Answers

Question 1

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 shift threshold voltage to - 1 V are __________ .

A. 8.6 x 1011/cm2, p-type
B. 8.6 x 1011/cm2, n-type
C. 0.86 x 109/cm2, p-type
D. 1.02 x 1012/cm2, n-type

Question 2

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 __________ .

A. - 2 V
B. 2 V
C. - 4 V
D. 4 V

Question 3

A noiseless 3 KHz channel can transmit binary at the rate __________ .

A. 12000 bps
B. 10000 bps
C. 6000 bps
D. 3000 bps

Question 4

A radar receiver has a noise figure of 10 dB at 300 K having a bandwidth of 2.5 MHz. The minimum power it can receive is

A. 3.45 x 10-15 W
B. 1.38 x 10-15 W
C. 7.5 x 10-15 W
D. 93.15 x 10-15 W

Question 5

A rectangular waveguide, in dominant TE mode, has dimensions 10 cm x 15 cm. The cut off frequency is

A. 10 GHz
B. 1 GHz
C. 15 GHz
D. 25 GHz

Question 6

A transmission line has a characteristic impedance of 50 Ω and a resistance of 0.1 Ω/m, if the line is distortion less, the attenuation constant (in Np/m) is

A. 500
B. 5
C. 0.014
D. 0.002

Question 7

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

A. 50 Mbps
B. 100 Mbps
C. 36 Mbps
D. 72 Mbps

Question 8

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

A. 1.5 x 108 m/s
B. 5.5 x 108 m/s
C. 3.46 x 108 m/s
D. 0.18 x 107 m/s

Question 9

As the temperature increases the mobility of electrons __________ .

A. decreases because the number of carries increases with increased collisions
B. increases because the number of carries decreases with decreased collisions
C. remains same
D. none of the above

Question 10

Who is the author of The Last Lesson?

A. Jane Austen
B. Rabindranath Tagore
C. Alphonse Daudat
D. None of these

Question 11

Consider the amplitude modulated (AM) signal Ac cos ωct + 2 cos ωmt cos ωct For demodulating the signal using envelope detector, the minimum value of Ac should be

A. 2
B. 1
C. 0.5
D. 0

Question 12

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

A. (1) is true and (2) is false
B. (1) and (2) both are true
C. (1) is false and (2) is true
D. (1) and (2) both are false

Question 13

Denominator polynomial of a transfer function of certain network is: s3 + s2 + 2s + 24 Then the network is:

A. stable
B. oscillatory
C. unstable
D. depends on numerator polynomial

Question 14

For a given voltage, four heating coils will produce maximum heat when connected

A. all in parallel
B. all in series
C. with two parallel pairs in series
D. one pair in parallel with the other two in series

Question 15

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

A. 32 KΩ
B. 16 KΩ
C. 8 KΩ
D. 4 KΩ

Question 16

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

A. 0.625 V
B. 0.656 V
C. 0.525 V
D. insufficient data

Question 17

In a semiconductor material. The hole concentration is found to be 2 x 2.5 x 1015 cm-3. If mobility of carriers is 0.13 m2/ v-s. Then find the current density if electric field intensity is 3.62 x 10-19

A. 7.6237 x 10-4 A/cm2
B. 7.6237 x 10-5 A/cm2
C. 7.6237 x 10-3 A/cm2
D. none of these

Question 18

Radiation resistance of an antenna is 54 Ω and loss resistance is 6 Ω. If antenna has power gain of 10, then directivity is:

A. 9
B. 11.11
C. data not sufficient
D. 10

Question 19

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 __________ .

A. 2
B. 3
C. 4
D. 1

Question 20

The analog signal given below is sampled at 1200 samples per second. m(t) = 2 sin 120 pt + 3 sin 240 pt + 4 sin 360 pt + 5 sin 480 pt + 6 sin 600 pt + 7 sin 720 pt. The folding (maximum) frequency is __________ .

A. 300 Hz
B. 360 Hz
C. 600 Hz
D. 480 Hz

Question 21

The antenna current of an AM transmitter is 8 A, when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by a single sine wave. Determine the antenna current when the percent of modulation changes to 0.8

A. 9.19 A
B. 9.91 A
C. 10.56 A
D. 8.61 A

Question 22

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

A. C + (A ⊕ B)
B. (A + B + C)(A + B + C)
C. (A + B + C)(A + B + C)(A + B + C)
D. (A + B + C)(A + B + C)(A + B + C)

Question 23

The gradient of any scalar field always yields __________ .

A. a solenoidal field
B. a conservative field
C. an irrotational field
D. none of these

Question 24

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

A. V-1
B. em.V-1
C. V.cm-1
D. V.s

Question 25

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

A. 8.95 eV
B. -8.95 eV
C. 7.326 eV
D. -7.326 eV

Question 26

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

A. 2 kV, 0.5 kV
B. 1 kV, 0.5 kV
C. 0.75 kV, 0.25 kV
D. 0.5 kV, 1.5 kV

Question 27

What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz?

A. 0.6698
B. 0.7698
C. 0.503
D. 0.6598

Question 28

When phase-lag compensation is used in a system, then gain cross over frequency, bandwidth and undamped frequency are respectively

A. Increased, Increased, Increased
B. Increased, Increased, Decreased
C. Increased, Decreased, Decreased
D. Decreased, Decreased, Decreased