Gibilisco - Amplifiers And Oscillators

19 Questions | Total Attempts: 350

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Gibilisco - Amplifiers And Oscillators

Questions and Answers
  • 1. 
    The decibel is a unit of
    • A. 

      Relative signal strength.

    • B. 

      Voltage.

    • C. 

      Power.

    • D. 

      Current.

  • 2. 
    An oscillator at RF requires the use of
    • A. 

      A common drain or common collector circuit.

    • B. 

      A stage with gain.

    • C. 

      A tapped coil.

    • D. 

      A quartz crystal.

  • 3. 
    Suppose a circuit is found to have a gain figure of −15 dB. Which of the following statementsis true?
    • A. 

      The output signal is stronger than the input signal.

    • B. 

      The input signal is stronger than the output signal.

    • C. 

      The input signal is 15 times as strong as the output signal.

    • D. 

      The output signal is 15 times as strong as the input signal.

  • 4. 
    In an oscillator circuit, the feedback should be
    • A. 

      As great as possible.

    • B. 

      Kept to a minimum.

    • C. 

      Just enough to sustain oscillation.

    • D. 

      Done through a transformer whose wires can be switched easily.

  • 5. 
    A power gain of 44 dB is equivalent to which of the following output/input power ratios?
    • A. 

      44:1

    • B. 

      160:1

    • C. 

      440:1

    • D. 

      25,000:1

  • 6. 
    An RF choke
    • A. 

      Passes RF signals but blocks dc.

    • B. 

      Passes both RF signals and dc.

    • C. 

      Passes dc but blocks RF signals.

    • D. 

      Blocks both dc and RF signals.

  • 7. 
    The optimum capacitance values in an amplifier circuit depend on
    • A. 

      The power-supply voltage.

    • B. 

      The power-supply polarity.

    • C. 

      The input signal strength.

    • D. 

      The input signal frequency.

  • 8. 
    An oscillator might fail to start for any of the following reasons, except
    • A. 

      Low battery voltage.

    • B. 

      Low stage gain.

    • C. 

      In-phase feedback.

    • D. 

      A high-impedance load.

  • 9. 
    In which of the following FET amplifier types does drain current flow for exactly 50 percentof the signal cycle?
    • A. 

      Class A

    • B. 

      Class AB1

    • C. 

      Class AB2

    • D. 

      Class B

  • 10. 
    The frequency at which a quartz crystal oscillator produces energy is largely dependent on
    • A. 

      The load impedance.

    • B. 

      The physical thickness of the quartz wafer.

    • C. 

      The amount of resistance through the crystal.

    • D. 

      The power-supply voltage.

  • 11. 
    Which bipolar amplifier type has some distortion in the signal wave, with collector currentduring most, but not all, of the cycle?
    • A. 

      Class A

    • B. 

      Class AB1

    • C. 

      Class AB2

    • D. 

      Class B

  • 12. 
    An RF oscillator usually
    • A. 

      Produces an output signal with an irregular waveshape.

    • B. 

      Has most or all of its energy at a single frequency.

    • C. 

      Produces a sound that depends on its waveform.

    • D. 

      Employs an RC circuit to determine the output amplitude.

  • 13. 
    A class C amplifier can be made linear by
    • A. 

      Reducing the bias.

    • B. 

      Increasing the drive.

    • C. 

      Using two transistors in push-pull.

    • D. 

      No means; a class C amplifier is always nonlinear.

  • 14. 
    A frequency synthesizer has
    • A. 

      High power output.

    • B. 

      High frequency drift rate.

    • C. 

      Exceptional stability.

    • D. 

      An adjustable waveshape.

  • 15. 
    A graphic equalizer is a form of
    • A. 

      Bias control for an NPN bipolar transistor.

    • B. 

      Gain control for an RF oscillator.

    • C. 

      Tone control that can be used in an audio amplifier.

    • D. 

      Circuit for adjusting the waveform of an RF oscillator.

  • 16. 
    If the impedance of the load connected to the output of an oscillator is extremely high,
    • A. 

      The frequency will drift excessively.

    • B. 

      The power output will be reduced.

    • C. 

      The oscillator might fail to start.

    • D. 

      It is no cause for concern; in fact, it is a good thing.

  • 17. 
    Suppose a certain bipolar-transistor PA is 66 percent efficient. The output power is 33 W.The dc collector power input is
    • A. 

      22 W.

    • B. 

      50 W.

    • C. 

      2.2 W.

    • D. 

      Impossible to determine without more information.

  • 18. 
    A tuned RF PA must always be
    • A. 

      Set to work over a wide range of frequencies.

    • B. 

      Adjusted for maximum power output.

    • C. 

      Operated at an even harmonic of the input frequency.

    • D. 

      Operated in class C.

  • 19. 
    Class B amplification can be used to obtain low distortion for audio applications
    • A. 

      By connecting two amplifiers in cascade, thereby maximizing the gain and generating a pure sine wave output.

    • B. 

      By biasing the bipolar transistor or FET beyond cutoff or pinchoff, thereby ensuring that the output is in phase with the input.

    • C. 

      By connecting two identical bipolar transistors or FETs, biased exactly at cutoff or pinchoff, in a push-pull configuration.

    • D. 

      By biasing the bipolar transistor or FET in the middle of the straight-line portion of the characteristic curve.

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