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ECE Objective Questions { BJT Amplifiers and Transistor }

71. The oscillator that uses tapped capacitors in the tuned circuit is
A. Colpitts
B. astable multivibrator
C.(d) both (a) and (b)
D. none of the above

72. An oscillator produces oscillations due to
A. positive feedback
B. negative feedback
C. partly positive and partly negative feedback
D. neither positive nor negative feedback

73. The most stable sinewave oscillator with most simple circuit is
A. Colpitts
B. Armstrong
C. phase-shift circuit
D. crystal

74. For sustaining oscillations in an oscillator
A. feedback factor should be unity
B. phase shift should be 0?
C. feedback should be negative
D. both (a) and (b)

75. If Barkhausen criterion is not fulfilled by an oscillator circuit, it will
A. stop oscillating
B. produce damped waves continuously
C. become an amplifier
D. produce high-frequency whistles

76. Frequency stability in an oscillator can be achieved by
A. adjusting the phase shift
B. controlling its gain
C. incorporating a tuned circuit
D. employing automatic biasing

77. Gain stability in an oscillator is usually achieved by
A. using low-Q circuits
B. incorporating a tuned circuit
C. using negative feedback
D. controlling the gain

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