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Digital Electronics
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Multivibrators and 555 Timer
Comments
Question
A 22-kΩ resistor and a 0.02-µF capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?
Options
A. 0.44 ms
B. 0.501 ms
C. 0.66 ms
D. 0.70 ms
Correct Answer
0.501 ms
Multivibrators and 555 Timer problems
Search Results
1. Is the circuit given below an astable multivibrator or a monostable multivibrator?
Options
A. monostable
B. astable
Show Answer
Scratch Pad
Discuss
Correct Answer: monostable
2. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: to compare the input voltages to the internal voltage divider
3. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: duty cycle
4. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: the period of the waveform
5. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: astable
6. Triggering a retriggerable one shot during pulse generation will:
Options
A. time out the original pulse
B. extend the pulse to this trigger width
C. have no effect
D. double the original pulse width
Show Answer
Scratch Pad
Discuss
Correct Answer: extend the pulse to this trigger width
7. The monostable multivibrator circuit is not an oscillator because ________.
Options
A. its output switches between two states
B. it requires a trigger to obtain an output signal
C. it requires a sine wave input signal
D. the circuit does not require a dc power supply
Show Answer
Scratch Pad
Discuss
Correct Answer: it requires a trigger to obtain an output signal
8. Does the 74123 one shot have an internal timing resistor?
Options
A. yes
B. no
Show Answer
Scratch Pad
Discuss
Correct Answer: no
9. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: discharge the external capacitor to start the timing over again
10. 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
Show Answer
Scratch Pad
Discuss
Correct Answer: an
RC
time constant
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