Electronic Devices and Circuit Theory-Oscillator Circuits Questions and Answers

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Q11
In order to start up, a feedback oscillator requires
  • A negative feedback less than 1.
  • B positive feedback greater than 1.
  • C unity feedback equal to 1.
  • D no feedback.
Answer: Option B
Q12
The amplifier is unstable if the Nyquist curve plotted encloses (encircles) the –1 point, and it is stable otherwise.
  • A TRUE
  • B FALSE
Answer: Option A
Q13
Which of the following oscillators is (are) tuned oscillators?
  • A Colpitts
  • B Hartley
  • C Crystal
  • D All of the above
Answer: Option D
Q14
The Nyquist plot combines the two Bode plots of gain versus frequency and phase shift versus frequency on a single plot.
  • A TRUE
  • B FALSE
Answer: Option A
Q15
An input signal is needed for an oscillator to start.
  • A TRUE
  • B FALSE
Answer: Option B
Q16
The lead-lag circuit in the Wien-bridge oscillator has a resonant frequency at which the attenuation is
  • A 1/2
  • B 1/4.
  • C 1/3.
  • D 1/5.
Answer: Option C
Q17
The start-up gain of an oscillator must be ________ one.
  • A equal to
  • B less than
  • C greater than
Answer: Option C
Q18
In the IC phase-shift oscillator, what should the ratio of feedback resistor Rf to R1 be?
  • A Zero
  • B Greater than –29
  • C Less than 29
  • D Any value
Answer: Option B
Q19
At series resonance, the impedance of a crystal is
  • A minimum.
  • B maximum.
  • C equal.
  • D zero.
Answer: Option A
Q20
For frequencies up to 1 MHz, the ________ is the most widely used type of sinusoidal RC oscillator.
  • A Wien-bridge
  • B phase-shift
  • C twin-T
  • D [NIL]
Answer: Option A

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