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25)
The LM317 regulator provides a(n)
25)
A)
adjustable negative output voltage.
B)
fixed negative output voltage.
C)
fixed positive output voltage.
D)
adjustable positive output voltage.
Answer:
D
Explanation:
A)
B)
C)
D)
26)
A voltage regulator with a no-load output dc voltage of 12 V is connect to a load with a resistance
of 10 . If the load resistance decreases to 7.5 , the load voltage will decrease to 10.9 V. The load
current will be ________ and the percent load regulation is ________.
26)
A)
1.45 A, 90.8%
B)
1.6 A, 90.8%
C)
1.6 A, 9.17%
D)
1.45 A, 10.09%
Answer:
D
Explanation:
A)
B)
C)
D)
11
27)
Refer to the figure above. Which of these circuits is known as a series regulator?
27)
A)
(a)
B)
(b)
C)
(c)
D)
None of the above.
Answer:
A
Explanation:
A)
B)
C)
D)
12
28)
Refer to the figure above. The purpose for the op-amp is to
28)
A)
limit the input voltage to the circuit.
B)
amplify the error signal.
C)
supply a reference voltage.
D)
sense the error signal.
Answer:
B
Explanation:
A)
B)
C)
D)
29)
If the load is shorted, the pass transistor has the least power dissipation when the regulator has
29)
A)
a high zener voltage.
B)
low efficiency.
C)
foldback limiting.
D)
buck topology.
Answer:
C
Explanation:
A)
B)
C)
D)
13
30)
Refer to the figure above. If the output voltage tends to increase due to a decrease in load current,
the transistor will conduct for ________ time each cycle.
30)
A)
exactly half the
B)
the same
C)
a shorter
D)
a longer
Answer:
C
Explanation:
A)
B)
C)
D)
31)
A voltage regulator with a no-load dc output of 15 V is connected to a load with a resistance of 12
. If the load voltage decreases to 14.5 V, the percent regulation would be
31)
A)
3.45%.
B)
3.33%.
C)
100%.
D)
96.7%.
Answer:
A
Explanation:
A)
B)
C)
D)
32)
To get more output voltage from a step-down switching regulator, you have to
32)
A)
increase the duty cycle.
B)
decrease the duty cycle.
C)
decrease the input voltage.
D)
increase the switching frequency.
Answer:
A
Explanation:
A)
B)
C)
D)
14
33)
Refer to the figure above. Which of these circuits is known as a step-up switching regulator?
33)
A)
(a)
B)
(b)
C)
(c)
D)
None of the above.
Answer:
D
Explanation:
A)
B)
C)
D)
15
34)
Refer to the figure above. If a solder splash shorted the ends of R1 to each other, the result would be
that
34)
A)
the output voltage would not change.
B)
the op-amp would fail.
C)
Q1 would open.
D)
the zener would fail.
Answer:
D
Explanation:
A)
B)
C)
D)
35)
Refer to the figure above. The purpose for the diode D1 is to
35)
A)
supply a reference voltage.
B)
amplify the error signal.
C)
limit the input voltage to the circuit.
D)
sense the error signal.
Answer:
A
Explanation:
A)
B)
C)
D)
16
36)
With foldback current limiting, the load voltage approaches zero, and the load current approaches
36)
A)
infinity.
B)
a small value.
C)
the zener current.
D)
a destructive level.
Answer:
B
Explanation:
A)
B)
C)
D)
37)
An increase of line voltage into a power supply usually produces
37)
A)
an increase in load voltage.
B)
less power dissipation in the rectifier diodes.
C)
a decrease in load resistance.
D)
a decrease in efficiency.
Answer:
A
Explanation:
A)
B)
C)
D)
38)
Refer to the figure above. This circuit is brought in for repair. The measured output voltage was 25
V under all load conditions. A possible cause of this symptom might be that
38)
A)
Vin has decreased.
B)
R2 has opened.
C)
R3 has opened.
D)
Q1 base-emitter has opened.
Answer:
B
Explanation:
A)
B)
C)
D)
17
39)
Refer to the figure above. An increase in VOUT will cause Q1 to
39)
A)
conduct more.
B)
conduct the same.
C)
open.
D)
conduct less.
Answer:
D
Explanation:
A)
B)
C)
D)
40)
If the output of a voltage regulator varies from 20 to 19.8 V when the line voltage varies over its
specified range, the load regulation is
40)
A)
0.
B)
5%.
C)
2%.
D)
1%.
Answer:
D
Explanation:
A)
B)
C)
D)
TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false.
41)
Most voltage regulators include some kind of protection circuitry.
41)
Answer:
True
False
Explanation:
42)
A zener diode is sometimes used as a voltage regulator.
42)
Answer:
True
False
Explanation:
43)
In a shunt regulator, the control element is in series with the load.
43)
Answer:
True
False
Explanation:
44)
Switching regulators are very efficient.
44)
Answer:
True
False
Explanation:
18
45)
Line regulation is the percentage change in input voltage for a given change in output voltage.
45)
Answer:
True
False
Explanation:
19
