# 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°)

(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

(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

ANSWER: In the middle of the active region

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

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

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

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

(6) In general the gain of an amplifier is

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

(7) A IGFED is a

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

(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

(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

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

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

(11) Logarithmic amplifiers are used in

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

(12) Amplifier that gives highest gain is

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

(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

(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

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

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

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

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

(18) The power output will be

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

(19) The power extended in the transistor will be

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

(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

(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

(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

(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

(24) A pulse transformer comprises of

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

(25) A boot strap generally incorporates

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

(26) The third harmonic of 300 Hz is

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

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

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

(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

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

(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

(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

(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

(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

ANSWER: 10 % of the central frequency

(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

(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

(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

(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