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 ________.

value of the RC timing components

magnitude of the dc supply voltage

Determine tHI and tLO for the circuit given below.

tHI¬†=¬†6.24 s, tLO¬†=¬†7.95 s

tHI¬†=¬†7.95 s, tLO¬†=¬†6.24 s

tHI¬†=¬†6.24 s, tLO¬†=¬†7.95 s

tHI¬†=¬†3.97 s, tLO¬†=¬†3.21 s

tHI¬†=¬†3.21 s, tLO¬†=¬†3.97 s

Triggering a retriggerable one shot during pulse generation will:

extend the pulse to this trigger width

double the original pulse width

The monostable multivibrator circuit is not an oscillator because ________.

it requires a sine wave input signal

its output switches between two states

it requires a trigger to obtain an output signal

it requires a sine wave input signal

the circuit does not require a dc power supply

Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?

It has no internal timing resistor.

It has an active-HIGH reset, which terminates all timing functions.

It has no internal timing resistor.

To obtain a 50% duty cycle in an astable 555 timer circuit:

RA = RB and short RB with a diode during the capacitor charging cycle

capacitor voltage must rise above 1/3 VCC

tLO = tHI, RA = RB, and short RB with a diode during the capacitor charging cycle

The output of the astable circuit ________.

is LOW until a trigger is received

constantly switches between two states

is LOW until a trigger is received

is HIGH until a trigger is received

What is the difference between a retriggerable one shot and a nonretriggerable one shot?

The nonretriggerable can only be triggered once.

The retriggerable can be triggered many times.

The output pulse can be stretched with a nonretriggerable.

The output pulse can be stretched with a retriggerable.

When a capacitor charges:

the voltage across the plates rises exponentially

the circuit current falls exponentially

the capacitor charges to the source voltage in 5√óRC seconds

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

Rint¬†=¬†4 k, Cext¬†=¬†0.012 nF

Rint¬†=¬†2 k, Cext¬†=¬†0.012 nF

Rint¬†=¬†2 k, Cext¬†=¬†0.012 F

Rint¬†=¬†4 k, Cext¬†=¬†0.012 nF

Rint¬†=¬†4 k, Cext¬†=¬†0.012 F

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

VOH¬†=¬†10 V, VOL¬†=¬†0 V

VOH¬†=¬†10 V, VOL¬†=¬†0.1 V

VOH¬†=¬†8.5 V, VOL¬†=¬†0 V

VOH¬†=¬†8.5 V, VOL¬†=¬†0.1 V

What does the discharge transistor do in the 555 timer circuit?

charge the external capacitor to stop the timing

charge the external capacitor to start the timing over again

discharge the external capacitor to stop the timing

discharge the external capacitor to start the timing over again

What is the difference between an astable multivibrator and a monostable multivibrator?

The astable needs to be clocked.

The monostable is free running.

53 + Mcqs in Multivibrators And 555 Timer in Digital Electronics Page 1 McqOptions

1.	The internal circuitry of the 555 timer consists of ________, an flip-flop, a transistor switch, an output buffer amplifier, and a voltage divider.
A.	a comparator
B.	a voltage amplifier
C.	two comparators
D.	a peak detector
Answer» D. a peak detector

Discussion

2.	With most monostable multivibrators, what is the output when no input trigger has occurred?
A.	LOW
B.	+5 V
C.	SET
D.	HIGH
Answer» B. +5 V

Discussion

3.	The bistable multivibrator is an flip-flop.
A.	True
B.	False
Answer» C.

Discussion

4.	The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at .
A.	True
B.	False
Answer» C.

Discussion

5.	A 0.3-F capacitor has an initial charge of 2.7 V. If it is discharged through a 10-k resistor for 6.5 ms, how much voltage will be left across the capacitor?
A.	0.0 V
B.	0.309 V
C.	2.7 V
D.	2.295 V
Answer» C. 2.7 V

Discussion

6.	A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?
A.	0.44 ms
B.	0.501 ms
C.	0.66 ms
D.	0.70 ms
Answer» C. 0.66 ms

Discussion

7.	A multivibrator is a circuit that changes between two digital levels on a continuous, free-running basis or on demand.
A.	1
B.
Answer» B.

Discussion

8.	When the 74123, a retriggerable monostable multivibrator device, ends its timing cycle it must be started all over again.
A.	1
B.
Answer» C.

Discussion

9.	Timing accuracy of more than eight significant digits can be easily achieved by using quartz crystals.
A.	1
B.
Answer» C.

Discussion

10.	A monostable multivibrator is commonly called a two shot.
A.	1
B.
Answer» C.

Discussion

11.	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 ________.
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
Answer» B. amplitude of the input trigger

Discussion

12.	A single Schmitt trigger inverter is all that is needed to build a simple astable multivibrator.
A.	1
B.
Answer» C.

Discussion

13.	A crystal demonstrates the ________ effect when a mechanical force across the crystal causes a small voltage to be generated.
A.	photoelectric
B.	Co-pitts
C.	piezoelectric
D.	flywheel
Answer» D. flywheel

Discussion

14.	A comparator simply outputs a HIGH or LOW based on a comparison of the voltage levels at its input.
A.	1
B.
Answer» B.

Discussion

15.	What is another name for a bistable multivibrator?
A.	an on-off switch
B.	an oscillator
C.	a flip-flop
Answer» D.

Discussion

16.	Determine tHI and tLO for the circuit given below.
A.	tHI¬†=¬†7.95 s, tLO¬†=¬†6.24 s
B.	tHI¬†=¬†6.24 s, tLO¬†=¬†7.95 s
C.	tHI¬†=¬†3.97 s, tLO¬†=¬†3.21 s
D.	tHI¬†=¬†3.21 s, tLO¬†=¬†3.97 s
Answer» B. tHI¬†=¬†6.24 s, tLO¬†=¬†7.95 s

Discussion

17.	Triggering a retriggerable one shot during pulse generation will:
A.	time out the original pulse
B.	extend the pulse to this trigger width
C.	have no effect
D.	double the original pulse width
Answer» C. have no effect

Discussion

18.	What is the output pulse width of the waveform at the output of the circuit in the given figure?
A.	1.65 ms
B.	18.2 ms
C.	4.98 ms
D.	54.6 ms
Answer» C. 4.98 ms

Discussion

19.	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.
A.	a comparator
B.	a voltage amplifier
C.	two comparators
D.	a peak detector
Answer» D. a peak detector

Discussion

20.	What controls the output pulse width of a one shot?
A.	the clock frequency
B.	the width of the clock pulse
C.	an RL time constant
D.	an RC time constant
Answer» E.

Discussion

21.	An astable multivibrator requires:
A.	balanced time constants
B.	a pair of matched transistors
C.	no input signal
D.	dual J-K flip-flops
Answer» D. dual J-K flip-flops

Discussion

22.	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» E.

Discussion

23.	The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at Vout.
A.	1
B.
Answer» C.

Discussion

24.	With most monostable multivibrators, what is the Q output when no input trigger has occurred?
A.	LOW
B.	+5 V
C.	SET
D.	HIGH
Answer» B. +5 V

Discussion

25.	The monostable multivibrator circuit is not an oscillator because ________.
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
Answer» C. it requires a sine wave input signal

Discussion

26.	The bistable multivibrator is an R-C flip-flop.
A.	1
B.
C.	1
D.
Answer» C. 1

Discussion

27.	In the 74121, which is nonretriggerable, any triggers that come in before the end of the timing cycle are ignored.
A.	1
B.
Answer» B.

Discussion

28.	An astable 555 timer has the following number of stable states:
A.	0
B.	1
C.	2
D.	3
Answer» B. 1

Discussion

29.	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» C. It has no internal timing resistor.

Discussion

30.	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» B. timing resistor decreases

Discussion

31.	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?
A.	0.56
B.	0.44
C.	0.216
D.	0.174
Answer» D. 0.174

Discussion

32.	Does the 74123 one shot have an internal timing resistor?
A.	yes
B.	no
Answer» C.

Discussion

33.	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» D. none of the above

Discussion

34.	To obtain a 50% duty cycle in an astable 555 timer circuit:
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
Answer» B. RA = RB and short RB with a diode during the capacitor charging cycle

Discussion

35.	A monostable 555 timer has the following number of stable states:
A.	0
B.	1
C.	2
D.	3
Answer» C. 2

Discussion

36.	What is the duty cycle of the waveform at the output of the circuit given below?
A.	0.78
B.	0.56
C.	0.5
D.	0.44
Answer» C. 0.5

Discussion

37.	Is there any limit to the number of times that a 74123 can be retriggered?
A.	yes
B.	no
Answer» C.

Discussion

38.	The output of the astable circuit ________.
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
Answer» B. is LOW until a trigger is received

Discussion

39.	Is the circuit given below an astable multivibrator or a monostable multivibrator?
A.	monostable
B.	astable
Answer» B. astable

Discussion

40.	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» E.

Discussion

41.	What is the pulse width of the output of a 74123 if an external 4.7-k resistor and a 0.022-F capacitor are used?
A.	290 ms
B.	29 ms
C.	33.3 s
D.	290 s
Answer» D. 290 s

Discussion

42.	The ________ is defined as the time the output is active divided by the total period of the output signal.
A.	on time
B.	off time
C.	duty cycle
D.	active ratio
Answer» D. active ratio

Discussion

43.	What is the difference between a retriggerable one shot and a nonretriggerable one shot?
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.
Answer» E.

Discussion

44.	When a capacitor charges:
A.	the voltage across the plates rises exponentially
B.	the circuit current falls exponentially
C.	the capacitor charges to the source voltage in 5√óRC seconds
D.	all of the above
Answer» E.

Discussion

45.	Design a circuit using a 74121 to convert a 33-kHz, 30% duty cycle waveform to a 33-kHz, 60% duty cycle waveform.
A.	Rint¬†=¬†2 k, Cext¬†=¬†0.012 nF
B.	Rint¬†=¬†2 k, Cext¬†=¬†0.012 F
C.	Rint¬†=¬†4 k, Cext¬†=¬†0.012 nF
D.	Rint¬†=¬†4 k, Cext¬†=¬†0.012 F
Answer» C. Rint¬†=¬†4 k, Cext¬†=¬†0.012 nF

Discussion

46.	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» E.

Discussion

47.	What does the discharge transistor do in the 555 timer circuit?
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
Answer» E.

Discussion

48.	A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?
A.	0.44 ms
B.	0.501 ms
C.	0.66 ms
D.	0.70 ms
Answer» C. 0.66 ms

Discussion

49.	What is the difference between an astable multivibrator and a monostable multivibrator?
A.	The astable is free running.
B.	The astable needs to be clocked.
C.	The monostable is free running.
D.	none of the above
Answer» B. The astable needs to be clocked.

Discussion

50.	When extremely critical timing is required, a quartz crystal can be used.
A.	1
B.
C.	1
D.
Answer» B.

Discussion

Explore topic-wise MCQs in Digital Electronics.

The internal circuitry of the 555 timer consists of ________, an flip-flop, a transistor switch, an output buffer amplifier, and a voltage divider.

With most monostable multivibrators, what is the output when no input trigger has occurred?

The bistable multivibrator is an flip-flop.

The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at .

A 0.3-F capacitor has an initial charge of 2.7 V. If it is discharged through a 10-k resistor for 6.5 ms, how much voltage will be left across the capacitor?

A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?

A multivibrator is a circuit that changes between two digital levels on a continuous, free-running basis or on demand.

When the 74123, a retriggerable monostable multivibrator device, ends its timing cycle it must be started all over again.

Timing accuracy of more than eight significant digits can be easily achieved by using quartz crystals.

A monostable multivibrator is commonly called a two shot.

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 ________.

A single Schmitt trigger inverter is all that is needed to build a simple astable multivibrator.

A crystal demonstrates the ________ effect when a mechanical force across the crystal causes a small voltage to be generated.

A comparator simply outputs a HIGH or LOW based on a comparison of the voltage levels at its input.

What is another name for a bistable multivibrator?

Determine tHI and tLO for the circuit given below.

Triggering a retriggerable one shot during pulse generation will:

What is the output pulse width of the waveform at the output of the circuit in the given figure?

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.

What controls the output pulse width of a one shot?

An astable multivibrator requires:

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.

The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at Vout.

With most monostable multivibrators, what is the Q output when no input trigger has occurred?

The monostable multivibrator circuit is not an oscillator because ________.

The bistable multivibrator is an R-C flip-flop.

In the 74121, which is nonretriggerable, any triggers that come in before the end of the timing cycle are ignored.

An astable 555 timer has the following number of stable states:

Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?

The pulse width out of a one-shot multivibrator increases when the:

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?

Does the 74123 one shot have an internal timing resistor?

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?

To obtain a 50% duty cycle in an astable 555 timer circuit:

A monostable 555 timer has the following number of stable states:

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

Is there any limit to the number of times that a 74123 can be retriggered?

The output of the astable circuit ________.

Is the circuit given below an astable multivibrator or a monostable multivibrator?

Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?

What is the pulse width of the output of a 74123 if an external 4.7-k resistor and a 0.022-F capacitor are used?

The ________ is defined as the time the output is active divided by the total period of the output signal.

What is the difference between a retriggerable one shot and a nonretriggerable one shot?

When a capacitor charges:

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

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

What does the discharge transistor do in the 555 timer circuit?

A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?

What is the difference between an astable multivibrator and a monostable multivibrator?

When extremely critical timing is required, a quartz crystal can be used.