Multivibrators and 555 Timer Questions and Answers

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Q21
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.
  • A 3
  • B 7
  • C 10
  • D 13
Answer: Option D
Q22
What is another name for a bistable multivibrator?
  • A an on-off switch
  • B an oscillator
  • C a flip-flop
Answer: Option C
Q23
An astable 555 timer has the following number of stable states:
  • A 0
  • B 1
  • C 2
  • D 3
Answer: Option A
Q24
Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?
  • A monostable
  • B pulse stretching
  • C Schmitt triggering
  • D astable
Answer: Option D
Q25
Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?
  • 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
Answer: Option B
Q26
The pulse width out of a one-shot multivibrator increases when the:
  • A supply voltage increases
  • B timing resistor decreases
  • C UTP decreases
  • D timing capacitance increases
Answer: Option A
Q27
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?
  • A the shape of the waveform
  • B the amplitude of the waveform
  • C the period of the waveform
  • D none of the above
Answer: Option C
Q28
If Vcc of a 555 timer circuit is set to +10 V what is the level of output voltage from the circuit?
  • 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
Answer: Option D
Q29
When extremely critical timing is required, a quartz crystal can be used.
  • A TRUE
  • B FALSE
Answer: Option A
Q30
In the 74121, which is nonretriggerable, any triggers that come in before the end of the timing cycle are ignored.
  • A TRUE
  • B FALSE
Answer: Option A
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