Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
Switching regulators have ________ than linear regulators.
1)
A)
simpler circuitry
B)
more heat–sinking requirements
C)
greater efficiency
D)
lower efficiency
Answer:
Explanation:
A)
B)
C)
D)
2)
In a step–up regulator, the output voltage is filtered with a
2)
A)
choke–input filter.
B)
voltage divider.
C)
diode.
D)
capacitor–input filter.
Answer:
Explanation:
A)
B)
C)
D)
3)
Refer to the figure above. If a wire clipping were to short Q1 emitter to collector, the problem that
might result is
3)
A)
R2 would open.
B)
Q1 would fail.
C)
the zener would open.
D)
VOUT would increase to 25 V.
Answer:
Explanation:
A)
B)
C)
D)
1
4)
The main difference between the 78XX and 79XX series regulators is that
4)
A)
the 78XX series provides a positive fixed output voltage and the 79XX series provides a
negative fixed output voltage.
B)
the 78XX series is adjustable and the 79XX series is fixed.
C)
the 78XX series provides a negative fixed output voltage and the 79XX series provides a
positive fixed output voltage.
D)
the 78XX series is fixed and the 79XX series is adjustable.
Answer:
Explanation:
A)
B)
C)
D)
5)
Simple current limiting may produce too much heat in the
5)
A)
zener diode.
B)
ambient air.
C)
load resistor.
D)
pass transistor.
Answer:
Explanation:
A)
B)
C)
D)
6)
The 78XX series of voltage regulators produces an output voltage that is
6)
A)
unregulated.
B)
either positive or negative.
C)
negative.
D)
positive.
Answer:
Explanation:
A)
B)
C)
D)
2
7)
Refer to the figure above. The circuit that will also regulate the output voltage when Vin varies is
7)
A)
(a).
B)
(b).
C)
(c).
D)
All of the above.
Answer:
Explanation:
A)
B)
C)
D)
3
8)
If the output of a voltage regulator varies from 15 to 14.7 V between the minimum and maximum
load current, the load regulation is
8)
A)
2%.
B)
5%.
C)
0.
D)
1%.
Answer:
Explanation:
A)
B)
C)
D)
9)
An advantage of shunt regulation is
9)
A)
built–in short–circuit protection.
B)
high efficiency.
C)
low power dissipation in the pass transistor.
D)
little wasted power.
Answer:
Explanation:
A)
B)
C)
D)
10)
A voltage regulator has a no–load output of 18 V and a full load output of 17.3 V. The percent load
regulation is
10)
A)
96.1%.
B)
1.04%.
C)
0.25%.
D)
4.05%.
Answer:
Explanation:
A)
B)
C)
D)
11)
Without current limiting, a shorted load will probably
11)
A)
have a load voltage equal to the zener voltage.
B)
have too little load current.
C)
destroy diodes and transistors.
D)
produce zero load current.
Answer:
Explanation:
A)
B)
C)
D)
4
12)
Refer to the figure above. This circuit operates at a relatively ________ frequency and its efficiency
is ________.
12)
A)
low, low
B)
high, high
C)
high, low
D)
low, high
Answer:
Explanation:
A)
B)
C)
D)
13)
Switching regulator configurations include
13)
A)
inverting.
B)
step–up.
C)
step–down.
D)
All of the above.
Answer:
Explanation:
A)
B)
C)
D)
14)
A series regulator is an example of a
14)
A)
linear regulator.
B)
ac–to–dc converter.
C)
shunt regulator.
D)
switching regulator.
Answer:
Explanation:
A)
B)
C)
D)
5
15)
Refer to the figure above. If R1 opened, VOUT would
15)
A)
decrease to zero.
B)
remain the same.
C)
increase.
D)
Cannot be determined.
Answer:
Explanation:
A)
B)
C)
D)
16)
Refer to the figure above. To increase the current handling capability of this regulator, beyond the 5
A rating of the transistor, the reasonable thing to do would be to
16)
A)
change the values of R2 and R3.
B)
place another transistor in series with Q1.
C)
place another transistor in parallel with Q1.
D)
increase the value of the zener diode.
Answer:
Explanation:
A)
B)
C)
D)
6
17)
The 7912 produces a regulated output voltage of
17)
A)
+12 V.
B)
–12 V.
C)
+9 V.
D)
+5 V.
Answer:
Explanation:
A)
B)
C)
D)
18)
A ________ maintains a constant output voltage by controlling the duty cycle of a switch in series
with the load.
18)
A)
series regulator
B)
switching regulator
C)
shunt regulator
D)
linear regulator
Answer:
Explanation:
A)
B)
C)
D)
19)
A 7805 regulator has a +20 V input. If the input and output pins of the regulator are shorted
together by a solder bridge, the output voltage will be
19)
A)
+5 V.
B)
0.7 V.
C)
+20 V.
D)
0 V.
Answer:
Explanation:
A)
B)
C)
D)
20)
Refer to the figure above. If the zener had a voltage rating of 3.7 V, Vout would be
20)
A)
20.2 V.
B)
18.2 V.
C)
25 V.
D)
7.1 V.
Answer:
Explanation:
A)
B)
C)
D)
7
21)
Refer to the figure above. Which of these circuits is known as a shunt regulator?
21)
A)
(a)
B)
(b)
C)
(c)
D)
(a) or (b)
Answer:
Explanation:
A)
B)
C)
D)
8
22)
________ is a measurement of how well the power supply maintains a constant output voltage with
changes in input voltage.
22)
A)
Line regulation
B)
Voltage control
C)
Load regulation
D)
Load voltage control
Answer:
Explanation:
A)
B)
C)
D)
23)
An advantage of a switching regulator is
23)
A)
the circuit is very efficient.
B)
voltages can be stepped–up or stepped–down.
C)
less heat and wasted power.
D)
All of the above.
E)
None of the above.
Answer:
Explanation:
A)
B)
C)
D)
E)
9
24)
Refer to the figure above. In all of these circuits, the zener is used
24)
A)
to supply the op–amp with VCC.
B)
to regulate the output voltage directly.
C)
to sense the change in output voltage.
D)
as a reference voltage.
Answer:
Explanation:
A)
B)
C)
D)
10