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Oscillators MCQs

Practice Oscillators MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1
Electronic Devices & CircuitsOscillators

For sustained sinusoidal oscillations, the Barkhausen criterion requires the loop-gain magnitude to be approximately unity and the net loop phase shift to be?

  • A0 degrees or an integer multiple of 360 degrees
  • B90 degrees only
  • C180 degrees only regardless of feedback sign
  • D45 degrees
Report an error
Correct Answer: A. 0 degrees or an integer multiple of 360 degrees
Explanation: At the oscillation frequency, the loop must provide positive regenerative feedback: |A beta| ≈ 1 and total loop phase shift 0 degrees modulo 360 degrees.
Reference: Standard analog electronics: Barkhausen criterion
Question 2
Electronic Devices & CircuitsOscillators

An RC phase-shift oscillator using an inverting amplifier commonly obtains approximately how much phase shift from its RC feedback network at the oscillation frequency?

  • A0 degrees
  • B90 degrees
  • C180 degrees
  • D360 degrees from each RC section
Report an error
Correct Answer: C. 180 degrees
Explanation: The inverting amplifier contributes about 180 degrees, while the RC network contributes another 180 degrees so the total loop phase shift is 360 degrees.
Reference: Standard analog electronics: RC phase-shift oscillator
Question 3
Electronic Devices & CircuitsOscillators

A Wien-bridge oscillator is widely used for generating?

  • ALow-distortion sinusoidal signals
  • BOnly square waves
  • COnly digital clock pulses above microwave frequencies
  • DDC voltage without feedback
Report an error
Correct Answer: A. Low-distortion sinusoidal signals
Explanation: The Wien-bridge oscillator is a common audio/low-frequency sine-wave oscillator capable of low distortion with suitable amplitude stabilization.
Reference: Standard analog electronics: Wien-bridge oscillator
Question 7
Analog ElectronicsOscillators

For sustained oscillation, the Barkhausen phase condition requires the total loop phase shift to be?

  • A90 degrees
  • B180 degrees only
  • C0 degrees or an integer multiple of 360 degrees
  • D45 degrees
Report an error
Correct Answer: C. 0 degrees or an integer multiple of 360 degrees
Explanation: Regenerative feedback requires a net loop phase of 0 degrees modulo 360 degrees at the oscillation frequency.
Reference: Standard analog electronics: oscillators
Question 8
Analog ElectronicsOscillators

A Wien-bridge oscillator is commonly used to generate?

  • ASinusoidal waveforms
  • BDC only
  • COnly sawtooth waves
  • DRandom noise only
Report an error
Correct Answer: A. Sinusoidal waveforms
Explanation: The Wien-bridge oscillator is widely used for low-distortion sinusoidal signal generation.
Reference: Standard analog electronics: oscillators
Question 9
Analog ElectronicsOscillators

For a three-section RC phase-shift oscillator using identical RC sections in the usual idealized analysis, the amplifier must provide a gain magnitude of at least approximately?

  • A1
  • B3
  • C29
  • D100
Report an error
Correct Answer: C. 29
Explanation: The three-section RC network attenuates the signal; the standard idealized condition requires amplifier gain magnitude of at least about 29.
Reference: Standard analog electronics: oscillators
Question 12
Analog ElectronicsOscillators

In a Hartley oscillator, the frequency-selective tank circuit primarily uses?

  • ATwo capacitors and one resistor
  • BTwo inductive sections and a capacitor
  • COnly three resistors
  • DA crystal with no reactive components
Report an error
Correct Answer: B. Two inductive sections and a capacitor
Explanation: A Hartley oscillator uses a tapped inductor or two inductive sections with a capacitor to form its resonant tank.
Reference: Standard analog electronics: oscillators
Question 13
Analog ElectronicsOscillators

In a Colpitts oscillator, the feedback network characteristically uses?

  • AA capacitive divider
  • BAn inductive divider only
  • CA resistive bridge only
  • DA transformer rectifier
Report an error
Correct Answer: A. A capacitive divider
Explanation: A Colpitts oscillator uses two capacitors forming a capacitive divider together with an inductor.
Reference: Standard analog electronics: oscillators
Question 14
Analog ElectronicsOscillators

A crystal oscillator is preferred when the main requirement is?

  • AVery poor frequency stability
  • BHigh frequency stability
  • CLarge DC voltage regulation
  • DLow input resistance
Report an error
Correct Answer: B. High frequency stability
Explanation: Quartz crystals have very high Q and stable resonant characteristics, giving excellent oscillator frequency stability.
Reference: Standard analog electronics: oscillators
Question 15
Analog ElectronicsOscillators

For a Wien-bridge oscillator, the lead-lag feedback network has an attenuation of approximately 1/3 at resonance, so the amplifier gain required for sustained oscillation is approximately?

  • A1
  • B2
  • C3
  • D29
Report an error
Correct Answer: C. 3
Explanation: At the balance frequency the Wien network returns about one-third of the output, so the amplifier must provide a gain of approximately 3.
Reference: Standard analog electronics: oscillators
Question 18
Analog ElectronicsOscillators

A high-Q resonant circuit is characterized by?

  • AA relatively narrow bandwidth around resonance
  • BA very broad bandwidth only
  • CZero stored energy
  • DNo frequency selectivity
Report an error
Correct Answer: A. A relatively narrow bandwidth around resonance
Explanation: For a resonator, Q is inversely related to fractional bandwidth; a higher Q means sharper resonance and narrower bandwidth.
Reference: Standard analog electronics: oscillators
Question 20
Electronic Devices & CircuitsOscillators

For sustained sinusoidal oscillation, the Barkhausen criterion requires the magnitude of loop gain to be approximately unity and total loop phase shift to be?

  • A0 degrees or an integer multiple of 360 degrees
  • B90 degrees only
  • C180 degrees only regardless of inversion
  • D45 degrees only
Report an error
Correct Answer: A. 0 degrees or an integer multiple of 360 degrees
Explanation: At the oscillation frequency, positive regenerative feedback requires |Aβ|≈1 and net loop phase 0° modulo 360°.
Reference: Standard analog electronics: Barkhausen criterion
Question 21
Electronic Devices & CircuitsOscillators

A Wien-bridge oscillator is especially suitable for generating?

  • ALow-distortion sinusoidal signals over audio and moderate frequencies
  • BDC only
  • CRandom digital pulses only
  • DMicrowave power without resonators
Report an error
Correct Answer: A. Low-distortion sinusoidal signals over audio and moderate frequencies
Explanation: The Wien bridge provides frequency-selective positive feedback and is widely used for low-distortion sine-wave generation.
Reference: Standard analog electronics: Wien-bridge oscillator
Question 23
Electronic Devices & CircuitsOscillators

A crystal oscillator achieves high frequency stability mainly because a quartz crystal has a very high?

  • AQuality factor Q
  • BForward current gain beta
  • CJunction capacitance only
  • DSlew rate
Report an error
Correct Answer: A. Quality factor Q
Explanation: Quartz resonators have very high Q, producing a narrow and stable resonance that gives excellent oscillator frequency stability.
Reference: Standard analog electronics: crystal oscillator