# Q1: 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.

# Q2: An astable multivibrator requires:

A balanced time constants
B a pair of matched transistors
C no input signal
D dual J-K flip-flops

# Q3: 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×RC seconds
D all of the above

A yes
B no

A 0.44 ms
B 0.501 ms
C 0.66 ms
D 0.70 ms

# Q6: 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

# Q7: 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 kCext = 0.012 nF
B Rint = 2 kCext = 0.012 F
C Rint = 4 kCext = 0.012 nF
D Rint = 4 kCext = 0.012 F

A LOW
B +5 V
C SET
D HIGH

# Q9: 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

A yes
B no

# Q11: What is another name for a bistable multivibrator?

A an on-off switch
B an oscillator
C a flip-flop

# Q12: 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 = tHIRA = RB, and short RB with a diode during the capacitor charging cycle

# Q13: An astable multivibrator requires:

A balanced time constants
B a pair of matched transistors
C no input signal
D dual J-K flip-flops

A LOW
B +5 V
C SET
D HIGH

A 0
B 1
C 2
D 3

# Q16: 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

# Q17: 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

# Q18: 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

# Q19: What is the function of the comparators in the 555 timer circuit?

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

A 1.65 ms
B 18.2 ms
C 4.98 ms
D 54.6 ms

# Q21: 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

A photoelectric
B Co-pitts
C piezoelectric
D flywheel

# Q23: 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

# Q24: 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

# Q25: 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

A 290 ms
B 29 ms
C 33.3 s
D 290 s

A astable
B monostable
C multistable
D bistable

A 56%
B 44%
C 21.6%
D 17.4%

A on time
B off time
C duty cycle
D active ratio

A 0
B 1
C 2
D 3

# Q31: An astable multivibrator requires:

A balanced time constants
B a pair of matched transistors
C no input signal
D dual J-K flip-flops

# Q32: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

A 0.0 V
B 0.309 V
C 2.7 V
D 2.295 V

A 3
B 7
C 10
D 13

# Q35: 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

A monostable
B astable

# Q37: 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

# Q38: 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

# Q39: 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

# Q40:What is the duty cycle of the waveform at the output of the circuit given below?

A 78%
B 56%
C 50%
D 44%

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