ELC 127
Chapter 14 Quiz
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Capacitor charge and discharge curves are
A) logarithmic.
B) exponential.
C) linear.
1)
D) sinusoidal.
2) Which of the following, along with appropriate R and C, makes for a simple astable multivibrator?
A) TTL inverter
B) Single flip-flop
C) Single NAND gate
D) Schmitt inverter
2)
3) A one-shot is another name for the ________ multivibrator.
A) astable
B) monostable
C) unstable
3)
D) bistable
4) Which type of multivibrator is a free-running oscillator with a square-wave output?
A) bistable
B) astable
C) monostable
D) all of the above
4)
5) Which components are added to a monostable multivibrator to determine the specific time
durations required at the output?
A) two resistors
B) a resistor and a capacitor
C) a resistor and a diode
D) an AND gate and an OR gate
5)
6) Which internal circuit is used to determine when a 555 timer changes states?
A) a voltage comparator
B) a flip-flop
C) a buffer
D) an RC network
6)
7) In astable operation, the time period of the 555 timer output is expressed as
A) tw = R(.693)
B) tw = Rext + Rint
C) tw = RextCext
D) tw = tLO + tHI
7)
8) The percentage of time that an astable multivibrator output waveform is HIGH is called the
A) period.
B) frequency.
C) time constant.
D) duty cycle.
8)
9) Which formula is correct when calculating time LOW (tLO) for an astable 555 timer output?
A) tLO = RBC(.693)
B) tLO = RAR B(.693)
C) tLO = RBC
D) tLO = RB(.693)
9)
10) Which formula is correct when calculating time HIGH (tHI) for an astable 555 timer output?
A) tHI = RBC(.693)
B) tHI = (RA + RB)C(.693)
C) tHI = RA(.693)
D) tHI = RARB(.693)
10)
11) An astable 555 timer is designed using the following external components: RA = 2 k , RB = 6.5 k
C = .01 µF. Calculate time LOW (tLO).
A) 45 µsec
B) 550 µsec
C) 325 msec
D) 105 µsec
12) An astable 555 timer is designed using the following external components: RA = 2 k , RB = 6.5 k
, C = .01 µF. Calculate time HIGH (tHI).
A) 550 µsec
B) 325 msec
C) 59 µsec
D) 40 µsec
1
,
11)
12)
13) If the output of an astable 555 timer is LOW for 716 µs and HIGH for 13.7 ms, the duty cycle is
A) 78%
B) 95%
C) 57.4%
D) 67.8%
13)
14) Which additional component must be added to an astable 555 timer charging path in order to
achieve duty cycles of 50% or less?
A) a flip-flop
B) a diode
C) an additional capacitor
D) an additional resistor
14)
15) Which formula is used to calculate the pulse width on a monostable 555 timer?
A) tw = RAC
B) tw = RAC(.693)
C) tw = RAC(1.1)
D) tw = RARB(1.1)
15)
16) Which resistor (RA) is necessary to generate a 60 µs pulse at the output of a monostable 555 timer if
a .005 µF capacitor is used?
A) 4.7 k
B) 10.9 k
C) 25 k
D) 2.2 k
16)
17) A monostable 555 timer is designed using the following external components: RA = 1.8 k , C = 400
pF. What is the pulse width (tw) of the output?
A) 3.1 ms
B) 0.79 µs
C) 2.4 µs
D) 1.14 µs
17)
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