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Home ‣ Digital Electronics ‣ Multivibrators and 555 Timer Comments
  • Question

  • What is the difference between an astable multivibrator and a monostable multivibrator?


  • Options
  • A. The astable is free running.
  • B. The astable needs to be clocked.
  • C. The monostable is free running.
  • D. none of the above

  • Correct Answer
  • The astable is free running. 

    • Multivibrators and 555 Timer problems

    Search Results

    • 1. What is the output pulse width of the waveform at the output of the circuit in the given figure?


    • Options
    • A. 1.65 ms
    • B. 18.2 ms
    • C. 4.98 ms
    • D. 54.6 ms
      • Discuss
    • 2. An astable 555 timer has the following number of stable states:

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. 3
      • Discuss
    • 3. Determine tHI and tLO for the circuit given below.


    • Options
    • A. tHI = 7.95 µs, tLO = 6.24 µs
    • B. tHI = 6.24 µs, tLO = 7.95 µs
    • C. tHI = 3.97 µs, tLO = 3.21 µs
    • D. tHI = 3.21 µs, tLO = 3.97 µs
      • Discuss
    • 4. Is there any limit to the number of times that a 74123 can be retriggered?

    • Options
    • A. yes
    • B. no
      • Discuss
    • 5. A crystal demonstrates the ________ effect when a mechanical force across the crystal causes a small voltage to be generated.

    • Options
    • A. photoelectric
    • B. Co-pitts
    • C. piezoelectric
    • D. flywheel
      • Discuss
    • 6. A retriggerable one shot has a pulse of 10 ms. 3 ms after being triggered, another trigger pulse is applied. The resulting output pulse will be ________ ms.

    • Options
    • A. 3
    • B. 7
    • C. 10
    • D. 13
      • Discuss
    • 7. Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?

    • Options
    • A. monostable
    • B. pulse stretching
    • C. Schmitt triggering
    • D. astable
      • Discuss
    • 8. If the resistor in the Schmitt trigger astable multivibrator is a variable resistor, what part of the output voltage waveform will change when the resistance is changed?

    • Options
    • A. the shape of the waveform
    • B. the amplitude of the waveform
    • C. the period of the waveform
    • D. none of the above
      • Discuss
    • 9. The ________ is defined as the time the output is active divided by the total period of the output signal.

    • Options
    • A. on time
    • B. off time
    • C. duty cycle
    • D. active ratio
      • Discuss
    • 10. What is the function of the comparators in the 555 timer circuit?

    • Options
    • A. to compare the output voltages to the internal voltage divider
    • B. to compare the input voltages to the internal voltage divider
    • C. to compare the output voltages to the external voltage divider
    • D. to compare the input voltages to the external voltage divider
      • Discuss

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