Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
A voltage regulator has a dc supply voltage of 50 V when the output is unloaded. When a load is
connected the output voltage is 46 V. What is the percent regulation?
1)
A)
8.7%
B)
92%
C)
4%
D)
None of the above
Answer:
A
A)
B)
C)
D)
2)
Fold–back limiting in a series regulator is provided by ________ .
2)
A)
a second comparator
B)
feedback from the load voltage
C)
negative feedback
D)
a second voltage divider
Answer:
D
A)
B)
C)
D)
3)
A filtered rectifier has a 15 Vdc output with 100 mVp–p of ripple. The peak output voltage for the
circuit is ________.
3)
A)
14.9 Vpeak
B)
15.05 Vpeak
C)
47.2 Vpeak
D)
15.1 Vpeak
Answer:
B
A)
B)
C)
D)
4)
Calculate the ripple of a capacitor filter for a peak rectified voltage of 40 V, a capacitor of 80 µF and
a 100 mA load current.
4)
A)
10.24%
B)
2.84%
C)
4.3%
D)
8.33%
Answer:
D
A)
B)
C)
D)
5)
The ________ rectifier has the highest fequency of ripple voltage.
5)
A)
full–wave
B)
half–wave
C)
bridge
D)
both B and C
Answer:
B, D
A)
B)
C)
D)
1
6)
Calculate the output voltage for the voltage regulator shown here.
6)
A)
8.0 V
B)
11.3 V
C)
20.0 V
D)
12.0 V
Answer:
B
A)
B)
C)
D)
7)
The ideal line percent regulation rating is ________.
7)
A)
50%
B)
100%
C)
zero
D)
75%
Answer:
C
A)
B)
C)
D)
8)
A capacitive filter is added to a half–wave rectifier. The initial value of capacitance is 22 µF. If this
value is increased to 100 µF, the ripple output from the circuit will ________.
8)
A)
decrease
B)
remain the same
C)
increase
D)
Cannot be predicted
Answer:
A
A)
B)
C)
D)
9)
Shunt voltage regulators require ________.
9)
A)
shorted–load protection
B)
load voltage sampling
C)
open–load protection
D)
high–frequency protection
Answer:
B
A)
B)
C)
D)
2
10)
A voltage regulator is rated for an output current range of IL= 0 to 40 mA. Under no–load
conditions the output voltage from the circuit is 4 Vdc. Under full–load conditions, the output
voltage from the circuit is 3.984 Vdc. What is the percent load regulation of the circuit?
10)
A)
0.4%
B)
2.5
C)
400%
D)
None of the above
Answer:
A
A)
B)
C)
D)
11)
The 7800 series of fixed regulator have a voltage range of ________ to ________ .
11)
A)
±5 V, ± 24 V
B)
depends on the manufacturer
C)
5 V, 24 V.
D)
2 V, 24 V
Answer:
C
A)
B)
C)
D)
12)
The voltage differential between the input and output voltage that results in the loss of regulation
is called the ________ .
12)
A)
diff voltage
B)
dropout voltage
C)
stable voltage
D)
reg voltage
Answer:
B
A)
B)
C)
D)
13)
The connections on a three–terminal, IC voltage regulator are ________.
13)
A)
A, B, gnd
B)
in/out, filter, gnd
C)
in, out, gnd
D)
R, C, gnd
Answer:
C
A)
B)
C)
D)
14)
An IC voltage regulator ________.
14)
A)
inproves line regulation
B)
reduces the power supply ripple output voltage
C)
improves load regulation
D)
All of the above
Answer:
D
A)
B)
C)
D)
3
15)
Calculate the output voltage for this improved series voltage regulator.
15)
A)
12.0 V
B)
18.5 V
C)
8.0 V
D)
20.0 V
Answer:
B
A)
B)
C)
D)
16)
A rectified dc voltage was measured with both an ac and a dc voltmeter. It was found that
Vdc = 50 V and Vac = 2.16 Vrms. What was the percent ripple?
16)
A)
0.432%
B)
4.32%
C)
0.86%
D)
6%
Answer:
B
A)
B)
C)
D)
17)
The typical parts of a power supply are ________.
17)
A)
a transformer
B)
voltage regulator
C)
diode rectifier and filter
D)
All of the above
Answer:
D
A)
B)
C)
D)
18)
Referring to this shunt voltage regulator, calculate the output voltage that the load sees.
18)
A)
12.7 V
B)
11.3 V
C)
20 V
D)
8.2 V
Answer:
A
A)
B)
C)
D)
4
19)
A dc voltage supply provides an output of 25 V under no–load condition. This output voltage
drops to 22.5 V under full–load condition. Calculate the percent voltage regulation.
19)
A)
2.5%
B)
90%
C)
11.1%
D)
10%
Answer:
C
A)
B)
C)
D)
20)
Which of the following is not a type of voltage regulator?
20)
A)
fixed positive
B)
variable polarity
C)
fixed negative
D)
adjustable
Answer:
B
A)
B)
C)
D)
21)
Calculate the approximate current through the Zener diode for this voltage regulator.
21)
A)
83.33 mA
B)
33 mA
C)
50 mA
D)
None of the above
Answer:
B
A)
B)
C)
D)
22)
A three–terminal voltage regulator affords several different types of ________ protection.
22)
A)
short–circuit
B)
thermal shut–down
C)
Both A and B
D)
Neither A nor B
Answer:
C
A)
B)
C)
D)
5
23)
In a discrete series voltage regulator, the voltage from the sampling circuit and the reference
voltage are appplied to the ________ .
23)
A)
thr transistor base
B)
comparator circuit
C)
control element
D)
the zener regulator
Answer:
B
A)
B)
C)
D)
24)
A rectifier is used to ________.
24)
A)
reduce the variations in a pulsating dc signal
B)
maintain a constant power supply dc output voltage
C)
convert ac to pulsating dc
D)
convert one dc level to another
Answer:
C
A)
B)
C)
D)
25)
For this shunt voltage regulator, determine the minimum load resistance that the voltage regulator
can drive without dropping out of regulation.
25)
A)
2.17 k
B)
117
C)
217
D)
2000
Answer:
C
A)
B)
C)
D)
26)
A capacitive filter is added to a full–wave rectifier. The value of capacitance is 22 µF. If the circuit
RL= 1000 , what is the circuit’s ripple factor r?
26)
A)
15.2%
B)
10.9%
C)
12.7%
D)
Cannot be determined from the information given
Answer:
D
A)
B)
C)
D)
6
27)
The term full load means ________.
27)
A)
no load resistance is present
B)
load resistance is at a maximum value
C)
load current is at a minimum value
D)
load resistance is at a minimum value
Answer:
D
A)
B)
C)
D)
28)
The basic power supply is made up of ________.
28)
A)
a filter, a follower, and a regulator
B)
a rectifier, a filter, and a regulator
C)
a regulator, a follower, and a rectifier
D)
None of the above
Answer:
B
A)
B)
C)
D)
29)
In an op–amp based series regulator, the zener voltage is developed at ________ .
29)
A)
the inverting op–amp input
B)
the non–inverting op–amp input
C)
the transistor base
D)
none of the above
Answer:
B
A)
B)
C)
D)
30)
A three–terminal voltage regulator loses regulation if the difference between the input voltage and
the expected regulated output voltage is less than ________.
30)
A)
90% expected regulated output voltage
B)
The input and the expected output voltage can be exactly same.
C)
2.0 V
D)
10% expected regulated output voltage
Answer:
C
A)
B)
C)
D)
31)
The ideal voltage regulator maintains a constant dc output voltage regardless of changes in
________.
31)
A)
its output voltage demand
B)
its input voltage
C)
its load current demand
D)
either its load current demand or its input voltage
Answer:
D
A)
B)
C)
D)
7
32)
The ________ the percent load regulation rating of a voltage regulator, the higher the quality of the
circuit.
32)
A)
lower
B)
larger the change in
C)
higher
D)
None of the above
Answer:
A
A)
B)
C)
D)
33)
Calculate the percent ripple for a RC filter if the inputs are Vdc = 150 V, Vr(rms) = 15 V. The filter
components are C1=C2= 50 µF, R = 500 and RL= 5 K.
33)
A)
1.27%
B)
0.884%
C)
4.39%
D)
0.572%
Answer:
D
A)
B)
C)
D)
34)
Calculate the approximate current through the Zener diode for this series voltage regulator.
34)
A)
6.4 mA
B)
14.8 mA
C)
9.6 mA
D)
16 mA
Answer:
A
A)
B)
C)
D)
35)
The reduction of the ac component of the output voltage of a rectifier is due to the ________
characteristic of the RC filter sections.
35)
A)
voltage divider
B)
charge and discharge
C)
current gain
D)
none of the above
Answer:
B
A)
B)
C)
D)
8
36)
The ability of an IC voltage regulator to attenuate any input ripple voltage is called its ________
rating.
36)
A)
ripple rejection ratio in dB
B)
ripple attenuation
C)
ripple elimination
D)
ripple reduction
Answer:
A
A)
B)
C)
D)
37)
If the load resitance increases, the ripple ________ .
37)
A)
increases
B)
does not change, only the filter affects ripple
C)
decreases
D)
increases, but only alightly
Answer:
A, C
A)
B)
C)
D)
9
Answer Key
Testname: C15
1)
A
2)
D
3)
B
4)
D
5)
B, D
6)
B
7)
C
8)
A
9)
B
10)
A
11)
C
12)
B
13)
C
14)
D
15)
B
16)
B
17)
D
18)
A
19)
C
20)
B
21)
B
22)
C
23)
B
24)
C
25)
C
26)
D
27)
D
28)
B
29)
B
30)
C
31)
D
32)
A
33)
D
34)
A
35)
B
36)
A
37)
A, C