# Multiple Choice Question (MCQ) of Electronics page-6

76. The negative feedback is applied in many oscillator circuits to

a) Increase its output impedance
b) Decrease its output impedance
c) Stabilize the frequency of the oscillators
d) Stabilize the output amplitude

Ans: (d)

77. The negative feedback used in the amplifiers will reduce the noise by the same factor as gain

a) True
b) False

Ans: (a)

78. Enumerate the four benefits of negative feedback used in the amplifiers

a) Increased input impedance
b) Reduced output impedance
c) Improved gain stability
d) Extended bandwidth

Ans: ()

79. When the same amount of current can be controlled from the low impedance source to high impedance source then this is called

a) Power amplification
b) Current amplification
c) Voltage amplification
d) Gain amplification

Ans: (c)

80. When the signal feedback to the amplifier circuit is proportional to the output current rather than output voltage, an amplifier is said to have

a) Power feedback
b) Voltage feedback
c) Current feedback
d) Signal feedback

Ans: (c)

81. An element is said to have negative resistance when

a) The element has negative temperature
b) The current/voltage curve has negative slope
c) The element has negative specific resistance
d) The current/voltage curve has positive slop

Ans: (b)

82. The feedback oscillator would oscillate at all frequencies for which

a) Aβ = 0
b) Aβ ≤ 1
c) Aβ ≥ 1
d) A β= 1

Ans: (c)

83. The phase-shift network fulfills the oscillation condition of regenerative feedback for only one frequency

a) True
b) False

Ans: (a)

84. When R and C are same for all three high pass filters in series the frequency of oscillation of oscillator will be

a) fo+4 = 1/2π √RC
b) f0+4 = 1/2π √3RC
c) f0+4 = 1/2π √6RC
d) f0+4 = 1/√RC

Ans: (c)

85. The turned circuit in the oscillator may be connected to

a) The grid circuit only
b) The plate circuit only
c) (a) or (b)
d) None of the above

Ans: (c)

86. The grid has no control over the electrons activities when the ionization of gas has occurred in the thyratron tube because

a) Grid becomes more negative
b) Reid because more positive
c) Grid is neutralized as it is surrounded by positive ions
d) Grid is disconnected from the circuit

Ans: (c)

87.The unijunction transistor can be used as a voltage divider

a) True
b) False

Ans: (a)

88. What will happen if the emitter current increases in the unijunction transistor

a) The junction resistance increases and emitter voltage decreases
b) The junction resistance decreases and the emitter voltage decreases
c) The junction resistance decreases and emitter voltage increases
d) The junction resistance decreases and emitter voltage increases

Ans: (b)

89. The tunnel diode cannot be used as a very stable relaxation oscillator

a) True
b) False

Ans: (a)

90. A grounded shield used in choppers ( to convert the d.c. balance signal in potentiometer to a.c. signal ) helps

a) To reduce the vibrational noise
b) To reduce the noise component from pick-up and leakage
c) To avoid the electrical shocks
d) To avoid the need of earth wire

Ans: (b)

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