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Digital Electronics
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Multivibrators and 555 Timer
Comments
Question
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
Correct Answer
It has an active-HIGH reset, which terminates all timing functions.
Multivibrators and 555 Timer problems
Search Results
1. 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.
Show Answer
Scratch Pad
Discuss
Correct Answer: The output pulse can be stretched with a retriggerable.
2. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: monostable
3. A monostable 555 timer has the following number of stable states:
Options
A. 0
B. 1
C. 2
D. 3
Show Answer
Scratch Pad
Discuss
Correct Answer: 1
4. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: 33.3 µs
5. 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.
R
int
= 2 kΩ,
C
ext
= 0.012 nF
B.
R
int
= 2 kΩ,
C
ext
= 0.012 µF
C.
R
int
= 4 kΩ,
C
ext
= 0.012 nF
D.
R
int
= 4 kΩ,
C
ext
= 0.012 µF
Show Answer
Scratch Pad
Discuss
Correct Answer:
R
int
= 2 kΩ,
C
ext
= 0.012 µF
6. With most monostable multivibrators, what is the
Q
output when no input trigger has occurred?
Options
A. LOW
B. +5 V
C. SET
D. HIGH
Show Answer
Scratch Pad
Discuss
Correct Answer: LOW
7. The output of the astable circuit ________.
Options
A. constantly switches between two states
B. is LOW until a trigger is received
C. is HIGH until a trigger is received
D. floats until triggered
Show Answer
Scratch Pad
Discuss
Correct Answer: constantly switches between two states
8. When a capacitor charges:
Options
A. the voltage across the plates rises exponentially
B. the circuit current falls exponentially
C. the capacitor charges to the source voltage in 5×
RC
seconds
D. all of the above
Show Answer
Scratch Pad
Discuss
Correct Answer: all of the above
9. The pulse width out of a one-shot multivibrator increases when the:
Options
A. supply voltage increases
B. timing resistor decreases
C. UTP decreases
D. timing capacitance increases
Show Answer
Scratch Pad
Discuss
Correct Answer: supply voltage increases
10. What is another name for a bistable multivibrator?
Options
A. an on-off switch
B. an oscillator
C. a flip-flop
Show Answer
Scratch Pad
Discuss
Correct Answer: a flip-flop
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