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Home Digital Electronics Multivibrators and 555 Timer Comments

  • Question
  • Design a circuit using a 74121 to convert a 33-kHz, 30% duty cycle waveform to a 33-kHz, 60% duty cycle waveform.


  • Options
  • A. Rint = 2 kΩ, Cext = 0.012 nF
  • B. Rint = 2 kΩ, Cext = 0.012 µF
  • C. Rint = 4 kΩ, Cext = 0.012 nF
  • D. Rint = 4 kΩ, Cext = 0.012 µF

  • Correct Answer
  • Rint = 2 kΩ, Cext = 0.012 µF 


  • Multivibrators and 555 Timer problems


    Search Results


    • 1. What is the duty cycle of the waveform at the output of the circuit given below?


    • Options
    • A. 78%
    • B. 56%
    • C. 50%
    • D. 44%
    • Discuss
    • 2. The internal circuitry of the 555 timer consists of ________, an R-S flip-flop, a transistor switch, an output buffer amplifier, and a voltage divider.

    • Options
    • A. a comparator
    • B. a voltage amplifier
    • C. two comparators
    • D. a peak detector
    • Discuss
    • 3. What controls the output pulse width of a one shot?

    • Options
    • A. the clock frequency
    • B. the width of the clock pulse
    • C. an RL time constant
    • D. an RC time constant
    • Discuss
    • 4. What does the discharge transistor do in the 555 timer circuit?

    • Options
    • A. charge the external capacitor to stop the timing
    • B. charge the external capacitor to start the timing over again
    • C. discharge the external capacitor to stop the timing
    • D. discharge the external capacitor to start the timing over again
    • Discuss
    • 5. Does the 74123 one shot have an internal timing resistor?

    • Options
    • A. yes
    • B. no
    • Discuss
    • 6. What is the pulse width of the output of a 74123 if an external 4.7-kΩ resistor and a 0.022-µF capacitor are used?

    • Options
    • A. 290 ms
    • B. 29 ms
    • C. 33.3 µs
    • D. 290 µs
    • Discuss
    • 7. A monostable 555 timer has the following number of stable states:

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. 3
    • Discuss
    • 8. Pulse stretching, time-delay, and pulse generation are all easily accomplished with which type of multivibrator circuit?

    • Options
    • A. astable
    • B. monostable
    • C. multistable
    • D. bistable
    • Discuss
    • 9. What is the difference between a retriggerable one shot and a nonretriggerable one shot?

    • Options
    • A. The nonretriggerable can only be triggered once.
    • B. The retriggerable can be triggered many times.
    • C. The output pulse can be stretched with a nonretriggerable.
    • D. The output pulse can be stretched with a retriggerable.
    • Discuss
    • 10. Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?

    • Options
    • A. It is a dual multivibrator.
    • B. It has an active-HIGH reset, which terminates all timing functions.
    • C. It has no internal timing resistor.
    • D. none of the above
    • Discuss


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