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Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
A varactor is a diode that
1)
A)
varies its resistance with temperature.
B)
changes its capacitance with voltage.
C)
emits light when forward-biased.
D)
switches very fast.
E)
exhibits an increase in reverse current with light intensity.
Answer:
B
Explanation:
A)
B)
C)
D)
E)
2)
The capacitance of a varactor diode
2)
A)
decreases as the reverse bias voltage increases.
B)
increases as the reverse bias voltage increases.
C)
is usually 1000 µF or more.
D)
remains constant as the bias voltage varies.
Answer:
A
Explanation:
A)
B)
C)
D)
3)
The correct way to illuminate an LED is to
3)
A)
place the LED in series with a resisitor and a 5 V dc supply with the cathode toward the
positive side of the supply.
B)
place the LED in forward bias directly across a 5 V dc supply.
C)
place the LED in reverse bias directly across a 5 V dc supply.
D)
place the LED in series with a resistor and a 5 V dc supply with the anode toward the positive
side of the supply.
Answer:
D
Explanation:
A)
B)
C)
D)
4)
Two types of reverse breakdown in a zener diode are
4)
A)
avalanche and zener.
B)
charge and discharge.
C)
avalanche and reverse.
D)
avalanche and forward.
Answer:
A
Explanation:
A)
B)
C)
D)
1
5)
A ________ diode maintains a constant voltage across it when operating in the breakdown
condition.
5)
A)
germanium
B)
silicon
C)
zener
D)
None of the above.
Answer:
C
Explanation:
A)
B)
C)
D)
6)
A Schottky diode
6)
A)
cannot operate properly at high frequencies.
B)
has a forward voltage drop of about 2 V.
C)
has no limit on maximum current.
D)
has a metal-to-semiconductor junction.
Answer:
D
Explanation:
A)
B)
C)
D)
7)
A diode with a negative-resistance characteristic is needed. The correct selection would be a
7)
A)
Schottky diode.
B)
varactor diode.
C)
Gunn diode.
D)
tunnel diode.
Answer:
D
Explanation:
A)
B)
C)
D)
8)
For zener diodes, the temperature coefficient is
8)
A)
always negative.
B)
always positive.
C)
negative for breakdown voltages less than 5 V and positive for breakdown voltages greater
than 6 V.
D)
always zero.
Answer:
C
Explanation:
A)
B)
C)
D)
9)
The radiation pattern for an LED
9)
A)
visually shows the color of the light.
B)
shows how directional the light is.
C)
shows the wavelength of the light.
D)
shows the current vs. voltage curve of the LED.
Answer:
B
Explanation:
A)
B)
C)
D)
2
10)
An OLED produces light by a process called
10)
A)
photonic light emission.
B)
electrophosphorescence.
C)
organic light emission.
D)
avalanche light emission.
Answer:
B
Explanation:
A)
B)
C)
D)
11)
Refer to the figure above. If the zener shorts,
11)
A)
VRL will be equal to zero.
B)
Vin will be equal to VR.
C)
there is no current through RL.
D)
All of the above.
Answer:
D
Explanation:
A)
B)
C)
D)
12)
Modern traffic signals and large video screens are implemented with
12)
A)
hot filament bulbs.
B)
PIN diodes.
C)
high intensity LED arrays.
D)
infrared photodiodes.
Answer:
C
Explanation:
A)
B)
C)
D)
13)
A photodiode is a diode that
13)
A)
varies its resistance with temperature.
B)
changes its capacitance with light intensity.
C)
emits light when forward-biased.
D)
switches very fast.
E)
exhibits an increase in reverse current with light intensity.
Answer:
E
Explanation:
A)
B)
C)
D)
E)
3
14)
Refer to the figure above. Measurements show that VRL has increased. Which of the following
faults, if any, could have caused this problem?
14)
A)
The zener opens.
B)
The zener shorts.
C)
R opens.
D)
Vin has decreased.
Answer:
A
Explanation:
A)
B)
C)
D)
15)
Refer to the figure above. If Vin decreases, IR will
15)
A)
increase.
B)
remain the same.
C)
decrease.
D)
Unable to determine.
Answer:
C
Explanation:
A)
B)
C)
D)
16)
Refer to (c) in the figure above. The symbol is for
16)
A)
a zener diode.
B)
an LED.
C)
a Schottky diode.
D)
a photodiode.
E)
a tunnel diode.
Answer:
D
Explanation:
A)
B)
C)
D)
E)
4
17)
The varactor is usually
17)
A)
unbiased.
B)
reverse-biased.
C)
forward-biased.
D)
operated in the breakdown region.
Answer:
B
Explanation:
A)
B)
C)
D)
18)
Data sheets for zener diodes usually specify the zener voltage at a particular test current designated
18)
A)
IZT.
B)
IS.
C)
IZK.
D)
IZM.
Answer:
A
Explanation:
A)
B)
C)
D)
19)
All of the following are characteristics of a laser diode except
19)
A)
emits light of a single color.
B)
emits monochromatic light.
C)
contains a pn junction.
D)
emits incoherent light.
Answer:
D
Explanation:
A)
B)
C)
D)
20)
Refer to the figure above. As long as the zener is in regulation,
20)
A)
there is no current through the zener.
B)
VRL will be equal to 0.7 V.
C)
there is no current through RL.
D)
the current (IRL) remains constant.
Answer:
D
Explanation:
A)
B)
C)
D)
5
21)
Refer to the figure above. If the load current increases, IR will ________ and IZ will ________.
21)
A)
remain the same, decrease
B)
increase, remain the same
C)
remain the same, increase
D)
decrease, remain the same
Answer:
A
Explanation:
A)
B)
C)
D)
22)
When the light increases, the reverse minority carrier current in a photodiode
22)
A)
increases.
B)
reverses direction.
C)
decreases.
D)
is unaffected.
Answer:
A
Explanation:
A)
B)
C)
D)
23)
The PIN diode, when reverse-biased, acts like a nearly constant
23)
A)
voltage source.
B)
current source.
C)
capacitance.
D)
resistance.
Answer:
C
Explanation:
A)
B)
C)
D)
24)
A Schottky diode is a diode that
24)
A)
varies its resistance with temperature.
B)
changes its capacitance with voltage.
C)
emits light when forward-biased.
D)
switches very fast.
E)
exhibits an increase in reverse current with light intensity.
Answer:
D
Explanation:
A)
B)
C)
D)
E)
6
25)
Refer to (b) in the figure above. The symbol is for
25)
A)
a zener diode.
B)
an LED.
C)
a Schottky diode.
D)
a photodiode.
E)
a tunnel diode.
Answer:
A
Explanation:
A)
B)
C)
D)
E)
26)
Refer to the figure above. If the load current increases in the zener regulator,
26)
A)
the zener current increases.
B)
the series current increases.
C)
the series current remains the same.
D)
Both B and C above.
Answer:
C
Explanation:
A)
B)
C)
D)
27)
When the source voltage increases in a zener regulator, the current that remains approximately
constant is the
27)
A)
series current.
B)
total current.
C)
load current.
D)
zener current.
Answer:
C
Explanation:
A)
B)
C)
D)
7
