# Multiple choice question for engineering

## Set 1

1. An amplifier operating from ±3V provide a 2.2V peak sine wave across a 100 ohm load when provided with a 0.2V peak sine wave as an input from which 1.0mA current is drawn. The average current in each supply is measured to be 20mA. What is the amplifier efficiency?

a) 20.2%

b) 25.2%

c) 30.2%

d) 35.2%

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2. In order to prevent distortion in the output signal after amplification, the input signal must be

a) Higher than the positive saturation level of the amplifier

b) Lower than the negative saturation level of the amplifier

c) Must lie with the negative and the positive saturation level of the amplifier

d) Both higher than the positive saturation level of the amplifier and lower than the negative saturation level of the amplifier

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3. The voltage gain of the amplifier is 8 and the current gain is 7. The power gain of the amplifier is

a) 56 db

b) 17.481 db

c) 34.963 db

d) 1 db

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4. Statement 1: Voltage gain of -5 means that the output voltage has been attenuated.

Statement 2: Voltage gain of -5db means that the output voltage has been attenuated.

a) Statement 1 and Statement 2 are true

b) Statement 1 and Statement 2 are false

c) Only Statement 1 is true

d) Only Statement 2 is true

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5. Which of the following isn’t true?

a) Both transformer and amplifier can provide voltage gain

b) Both transformer and amplifier can provide current gain

c) Both transformer and amplifier can provide power gain

d) None of the mentioned

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6. Symmetrically saturated amplifiers operating in clipping mode can be used to convert a sine wave to a

a) Square wave

b) Pseudo Square wave

c) Sawtooth wave

d) Triangular wave

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7. What is meant by stability of the an amplified signal?

a) The amplified signal must have a finite amplitude

b) The amplified signal should not have self oscillation

c) The input and the output signal must be proportional

d) The ratio of the input and the output signal must be finite

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8. If A_{v}, A_{i} and A_{p} represents the voltage gain, current gain and power gain ratio of an amplifier which of the below is not the correct expression for the corresponding values in decibel?

a) Current gain: 20 log A_{i} db

b) Voltage gain: 20 log A_{v} db

c) Power gain: 20 log A_{p} db

d) Power gain: 10 log A_{p}

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_{p}db.

9. An amplifier has a voltage gain of 100 V/V and a current gain of 1000A/A. the value of the power gain decibel is

a) 30 db

b) 40 db

c) 50 db

d) 60 db

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10. The units of voltage gain is

a) It has no units, it is a ratio

b) Decibels (db)

c) All of the mentioned

d) None of the mentioned

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_{o}) = output voltage/input voltage (V

_{i}). It is also expresses as 20 log (V

_{o}/V

_{i}) db.

## Set 2

(Q.1-Q.3) An AM signal is represented by x(t) = (20 + 4sin(500πt)) cos(2πt x 10^{5})V.

1. The modulation index is

a) 20

b) 4

c) 0.2

d) 10

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2. Total signal power is

a) 208 W

b) 204 W

c) 408 W

d) 416 W

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3. Total sideband power is

a) 4 W

b) 8 W

c) 16 W

d) 2 W

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4. An AM broadcast station operates at its maximum allowed total output of 50 kW with 80% modulation. The power in the intelligence part is

a) 12.12 kW

b) 31.12 kW

c) 6.42 kW

d) none of the mentioned

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5. The aerial current of an AM transmitter is 18 A when unmodulated but increases to 20 A when modulated.The modulation index is

a) 0.68

b) 0.73

c) 0.89

d) 0.95

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^{2})/2, therefore α is 0.68.

6. A modulating signal is amplified by a 80% efficiency amplifier before being combined with a 20 kW carrier to generate an AM signal. The required DC input power to the amplifier, for the system to operate at 100% modulation, would be

a) 5 kW

b) 8.46 kW

c) 12.5 kW

d) 6.25 kW

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7. A 2 MHz carrier is amplitude modulated by a 500 Hz modulating signal to a depth of 70%. If the unmodulated carrier power is 2 kW, the power of the modulated signal is

a) 2.23 kW

b) 2.36 Kw

c) 1.18 kW

d) 1.26 kW

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8. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.4 and 0.3. The resultant modulation index will be

a) 1.0

b) 0.7

c) 0.5

d) 0.35

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^{2}= 0.3

^{2}+ 0.4

^{2}= 0.5

^{2}or α = 0.5.

9. In a DSB-SC system with 100% modulation, the power saving is

a) 100%

b) 55%

c) 75%

d) 100%

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10. A 10 kW carrier is sinusoidally modulated by two carriers corresponding to a modulation index of 30% and 40% respectively. The total radiated power is

a) 11.25 kW

b) 12.5 kW

c) 15 kW

d) 17 kW

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^{2}+ 0.3

^{2}) or 11.25 kW.

## Set 3

(Q1-Q.6) An amplifier is measured to have an internal resistance of 10 kΩ, voltage gain of 100V/V and output resistance of 100 Ω. Also, when a load resistance of 1 kΩ is connected between the output resistance if found to decrease to 8 kΩ. If the amplifier is fed with the signal source having an internal resistance of 2 kΩ, then

1. Find Gm.

a) 1 A/V

b) 10 A/V

c) 100 A/V

d) 1000 A/V

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2. Find Av.

a) 9.09 V/V

b) 10 V/V

c) 90.9 V/V

d) 100 V/V

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3. Find Gvo.

a) 53.3 V/V

b) 63.3 V/V

c) 73.3 V/V

d) 83.3 V/V

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4. Find Gv.

a) 53.4 V/V

b) 72.7 V/V

c) 83.3 V/V

d) 90.9 V/V

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5. Find R out.

a) 146 Ω

b) 292 Ω

c) 584 Ω

d) 1168 Ω

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6. Find Ai.

a) 182 A/A

b) 364 A/A

c) 546 A/A

d) 728 A/A

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(Q.7-Q.10) The circuit shown below is a small sine wave signal with average zero and transistor ß =

7. Find the value of R(E) to establish a dc emitter current of about 0.5 mA.

a) 28.57 kΩ

b) 57.04 kΩ

c) 114.08 kΩ

d) 228.16 kΩ

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8. Find R(C) to establish a dc collector voltage of about +5V.

a) 5 kΩ

b) 10 kΩ

c) 15 kΩ

d) 20 kΩ

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_{c}= 15 – R

_{c}.I

_{c}5 = 15 – R

_{c}* 0.99 * 0.5m R

_{c}= 20.2kΩ = 20kΩ.

9. For R (L) = 10 kΩ and transistor Ro = 200 kΩ, determine the overall voltage gain.

a) -21 V/V

b) -42 V/V

c) -86 V/V

d) -123 V/V

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## Set 4

1. A solid copper sphere, 10 cm in diameter is deprived of 1020 electrons by a charging scheme. The charge on the sphere is

a) 160.2 C

b) -160.2 C

c) 16.02 C

d) -16.02 C

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^{20}, Q = ne = e 10

^{20}= 16.02 C. Charge on sphere will be positive.

2. A lightning bolt carrying 15,000 A lasts for 100 s. If the lightning strikes an airplane flying at 2 km, the charge deposited on the plane is

a) 13.33 C

b) 75 C

c) 1500 C

d) 1.5 C

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3. If 120 C of charge passes through an electric conductor in 60 sec, the current in the conductor is

a) 0.5 A

b) 2 A

c) 3.33 mA

d) 0.3 mA

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4. The energy required to move 120 coulomb through

3 V is

a) 25 mJ

b) 360 J

c) 40 J

d) 2.78 mJ

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5. Consider the circuit graph shown in figure below. Each branch of circuit graph represent a circuit element. The value of voltage V1 is

a) 30 V

b) 25 V

c) 20 V

d) 15 V

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6. Req = ?

a) 11.86 ohm

b) 10 ohm

c) 25 ohm

d) 11.18 ohm

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7. In the circuit the dependent source

a) supplies 16 W

b) absorbs 16 W

c) supplies 32 W

d) absorbs 32 W

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8. Twelve 6 resistor are used as edge to form a cube. The resistance between two diagonally opposite corner of the cube is (in ohm)

a) 5/6

b) 6/5

c) 5

d) 6

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9. The energy required to charge a 10 µF capacitor to 100 V is

a) 0.1 J

b) 0.05 J

c) 5 x 10^{(-9)} J

d) 10 x 10^{(-9)} J

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10. A capacitor is charged by a constant current of 2 mA and results in a voltage increase of 12 V in a 10 sec

interval. The value of capacitance is

a) 0.75 mF

b) 1.33 mF

c) 0.6 mF

d) 1.67 mF

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## Set 5

1. In which of the following configuration does a MOSFET works as an amplifier?

a) Common Source (CS)

b) Common Gate (CG)

c) Common drain (CD)

d) All of the mentioned

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2. The MOSFET in the following circuit is in which configuration?

a) Common Source (CS)

b) Common Gate (CG)

c) Common Drain (CD)

d) None of the mentioned

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3. The MOSFET in the following circuit is in which configuration?

a) Common Source (CS)

b) Common Gate (CG)

c) Common Drain (CD)

d) None of the mentioned

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4. The MOSFET in the following circuit is in which configuration?

a) Common Source (CS)

b) Common Gate (CG)

c) Common Drain (CD)

d) None of the mentioned

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(Q.5-Q.10) Reference circuit for Q.5-Q.10 The circuit below is the characterization for the amplifier as a functional block.

5. If the value of R_{in} for the common source configuration is R_{1} and that for common source with a source resistance configuration is R_{2} ideally. The ratio of R_{1}/R_{2} will be

a) R_{1}/R_{2} = 1

b) 0 < R_{1}/R_{2} < 1

c) R_{1}/R_{2} > 1

d) R_{1}/R_{2} = 0

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6. Which is true for the value of A_{vo} for common source (Represented by A_{1}) and common source with a source resistance (represented by A_{2}).

a) A_{1} = A_{2}

b) A_{1} > _{2}

c) A_{1} < A_{2}

d) |A_{1}| < |A_{2}|

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_{1}= -g

_{m}R

_{D}and A

_{2}= -g

_{m}R

_{D}/1+g

_{m}R

_{S}Reference circuit for Common source configuration Reference circuit for common source with source resistance R

_{S}

7. Which of the following is true for the voltage gain (AV) for the common source configuration (represented by A1) and the common gate configuration (represented by A2)?

a) A_{1} = A_{2}

b) |A_{1}| = |A_{2}| and A1 ≠ A_{2}

c) |A_{1}| > |A_{2}|

d) |A_{1}| < |A_{2}|

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_{1}= -g

_{m}(R

_{L}||R

_{D}) and A

_{1}= g

_{m}(R

_{L}||R

_{D}) Reference figure for common source configuration Reference figure for common gate configuration

8. The value of the voltage gain (A_{v}) for the common source with source resistance (represented by A_{1}) and common gate configuration (represented by A_{2}) are related to each other by

a) A_{1} > A_{2}

b) |A_{1}| > |A_{2}|

c) A_{1} < A_{2}

d) A_{1} > A_{2} and |A_{1}| > |A_{2}|

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_{1}= – g

_{m}(R

_{L}||R

_{D})/ 1 + g

_{m}R

_{S}and A

_{2}= g

_{m}(R

_{L}||R

_{D}) Reference figure for common source with source resistance configuration Reference figure for common gate configuration

9. In which of the following configuration is the input resistance (R_{i}) not equal to zero ideally?

a) Common source configuration

b) Common source configuration with source resistance

c) Common gate configuration

d) Source follower configuration

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10. Which of the following has A_{VO} independent of the circuit elements?

a) Common source configuration

b) Common gate configuration

c) Source follower configuration

d) None of the mentioned

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_{VO}= 1 source follower.