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Multivibrators and 555 Timer problems

  • 1. If Vcc of a 555 timer circuit is set to +10 V what is the level of output voltage from the circuit?

  • Options
  • A. VOH = 10 V, VOL = 0 V
  • B. VOH = 10 V, VOL = 0.1 V
  • C. VOH = 8.5 V, VOL = 0 V
  • D. VOH = 8.5 V, VOL = 0.1 V
    • Discuss
  • 2. In a typical IC monostable multivibrator circuit, at the falling edge of the trigger input, the output switches HIGH for a period of time determined by the ________.

  • Options
  • A. value of the RC timing components
  • B. amplitude of the input trigger
  • C. frequency of the input trigger
  • D. magnitude of the dc supply voltage
    • Discuss
  • 3. If a diode is connected across resistor RB (positive end up) in the given figure, what is the new duty cycle of the output waveform?

    Digital Electronics Multivibrators and 555 Timer: If a diode is connected across resistor RB (positive end up) in the given figure,


  • Options
  • A. 56%
  • B. 44%
  • C. 21.6%
  • D. 17.4%
    • Discuss
  • 4. To obtain a 50% duty cycle in an astable 555 timer circuit:

  • Options
  • A. tLO = tHI
  • B. RA = RB and short RB with a diode during the capacitor charging cycle
  • C. capacitor voltage must rise above 1/3 VCC
  • D. tLO = tHI, RA = RB, and short RB with a diode during the capacitor charging cycle
    • Discuss
  • 5. An astable multivibrator requires:

  • Options
  • A. balanced time constants
  • B. a pair of matched transistors
  • C. no input signal
  • D. dual J-K flip-flops
    • Discuss
  • 6. 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
  • 7. Is there any limit to the number of times that a 74123 can be retriggered?

  • Options
  • A. yes
  • B. no
    • Discuss
  • 8. Determine tHI and tLO for the circuit given below.

    Digital Electronics Multivibrators and 555 Timer: 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
  • 9. An astable 555 timer has the following number of stable states:

  • Options
  • A. 0
  • B. 1
  • C. 2
  • D. 3
    • Discuss
  • 10. What is the output pulse width of the waveform at the output of the circuit in the given figure?

    Digital Electronics Multivibrators and 555 Timer: 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

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