Amplifiers - Electronics Engineering test questions

Amplifiers - Electronics Engineering test questions

(1) Gain of an amplifier = 400, input signal to an amplifier = 0.5 cos (313 t). The output signal is represented as

(A) 20 sin (403 t)
(B) 20 cos (403 t)
(C) 400 cos (313 t)
(D) 400 cos (313 t + 90°)

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(2) Voltage gain of an amplifier is 200 and its power gain is 40. The current gain of an amplifier is

(A) 1/5
(B) 1/8
(C) 5
(D) 8000

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(3) In an amplifier the signal handling capacity will be high when the operating point is selected

(A) At the extremities of the active region
(B) Close to cut-off region
(C) In the middle of the active region
(D) Close to saturation

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(4) For 455KHz IF amplifier the circuit that would be used is

(A) Double tuned transformer
(B) Class C amplifier
(C) Resistance - loaded
(D) Video amplifier

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(5) The coupling that gives the highest gain in an amplifier is

(A) Capacitance coupling
(B) Impedance coupling
(C) Resistance coupling
(D) Transformer coupling

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(6) In general the gain of an amplifier is

(A) Imaginary
(B) Complex
(C) Real
(D) None of the above

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(7) A IGFED is a

(A) Half – power device
(B) Linear device
(C) Square law device
(D) 3/2 power law device

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(8) Consider a FET having gate-source bias of 2 V. The ac input signal is ±1.2 V.The class of operation is

(A) Class AB2
(B) Class A
(C) Class B
(D) Class C

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(9) In case of an audio amplifier the bandwidth can be extended from 20 Hz to

(A) 20,000 Hz
(B) 2000 Hz
(C) 10,000 Hz
(D) 100,000 Hz

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(10) The output impedance of an ideal op-amp is

(A) Zero
(B) 50 ohm
(C) 100 ohm
(D) Infinite

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(11) Logarithmic amplifiers are used in

(A) Adders
(B) Multipliers
(C) Dividers
(D) All of the above

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(12) Amplifier that gives highest gain is

(A) Depends on the circuitry
(B) Darlington pair
(C) Cascade amplifier
(D) Cascode amplifier

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(13) When an amplifier’s power is changed from 10 watts to 20 watts the equivalent dB gain will be

(A) 3 dB
(B) 2 dB
(C) 10 dB
(D) 6 dB

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(14) A push pull amplifier is used to balance out

(A) Even harmonics
(B) Odd harmonics
(C) Both even and odd harmonics
(D) Neither even nor odd harmonics
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For questions 15 and 16 refer to the data given below:

Consider two cascaded IF amplifier stages tuned to a frequency of 456 KHz. Bandwidth = 10KHz.

(15) What should be the quality factor if circuit is single tuned?

(A) 17.33
(B) 43.43
(C) 50.50
(D) 29.33

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(16) What should be the quality factor if circuit is double tuned?

(A) 61.72
(B) 41.72
(C) 51.72
(D) 31.72

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For questions 17 to 19 refer to the data given below:

A push pull class B amplifier uses two AC 126 transistors, transformer coupled to a speaker of 3 ohms. The turns ratio = 20 and supply voltage = 9V.Assume transformer to be ideal

(17) The maximum collector current will be

(A) 30 mA
(B) 20 mA
(C) 15 mA
(D) 1 mA

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(18) The power output will be

(A) 15 mW
(B) 30 mW
(C) 45 mW
(D) 135 mW

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(19) The power extended in the transistor will be

(A) 1.844 mW
(B) 184.4 mW
(C) 18.44 mW
(D) 1844 mW

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(20) Due to negative feedback, the second harmonic distortion in an amplifier is reduced from 5% to 1%. What should be the feedback ratio if the amplifier gain is 1000?

(A) 0.199
(B) 0.1
(C) 0.09
(D) 0.009

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(21) Which one of the following model is suitable to use for high frequency response of a transistor amplifier

(A) T-network
(B) Hybrid π
(C) Kelvin network
(D) Lattice network

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(22) Less capacitive reactance in shunt with an audio amplifier has the effect of

(A) More negative feedback
(B) Treble boost
(C) Bass cut
(D) Treble cut

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(23) The voltage gain of an amplifier is 100. On applying a negative feedback with β = 0.03, its gain will reduce to

(A) 10
(B) 70
(C) 25
(D) 5

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(24) A pulse transformer comprises of

(A) Ferrite core
(B) Iron core
(C) Copper core
(D) Air core

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(25) A boot strap generally incorporates

(A) CE configuration
(B) CB configuration
(C) Emitter follower
(D) None of the above

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(26) The third harmonic of 300 Hz is

(A) 100 Hz
(B) 900 Hz
(C) 300 Hz
(D) 2700 Hz

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(27) The 45° - 45° system refers to stereo for

(A) Crystal microphones
(B) Magnetic tape recorders
(C) Loudspeakers
(D) Phonograph records

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(28) For the frequency range of 40 Hz to 8Khz, the point B is desired to be effectively at the ground potential. If for effective bypassing the impedance of the capacitor Ce should not be more than 10 % of the resistance Re, the value of the capacitor Ce should be



(A) 10 μF
(B) 1 μF
(C) 10 pF
(D) 1 pF

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For questions 29 to 32 refer to the data given below:

An RF amplifier is tuned with a parallel LC circuit where L = 3.3 μH and C = 76pF

(29) The resonant frequency will be

(A) 100 Mhz
(B) 10 MHz
(C) 5 MHz
(D) 1 Mhz

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(30) When R of the coil is 2 Ω, Q of the tuned circuit will be

(A) 10.4
(B) 104
(C) 1.04
(D) 1040

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(31) The loaded Q of the tuned circuit, if the input to the next stage represents a shunt load of 10 KΩ, will be

(A) 22
(B) 11
(C) 44
(D) 33

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(32) For the loaded Q the half power bandwidth of this amplifier will be

(A) 151 KHz
(B) 200 KHz
(C) 303 KHz
(D) 400 KHz

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(33) A pass band of a narrow band amplifier is nearly

(A) 25 % of the central frequency
(B) 10 % of the central frequency
(C) 30 % of the central frequency
(D) 40 % of the central frequency

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(34) In RC coupled triode amplifier, the coupling capacitor used is usually a

(A) 0.05 μF paper capacitor
(B) 0.05 μF mica capacitor
(C) 0.05 μF ceramic capacitor
(D) 0.05 μF electrolytic capacitor

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(35) Consider a multistage amplifier having output voltage of 8.9 V. What will be the input voltage if the gain is 65 dB?

(A) 1 mV
(B) 25 mV
(C) 125 mV
(D) 5 mV

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(36) Two peaks are seen in the response curve of a double tuned circuit when the transformer has

(A) Tight coupling
(B) Excessive coupling
(C) Critical coupling
(D) Loose coupling

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(37) Which one of the statements given below is true?

(A) A typical value for α is 10 to 300
(B) A typical value for β is 0.98
(C) Quassi symmetry means the driver stages are PNP and output stages are NPN
(D) None of the above

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