Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
A PUT has a value of VGK = +8 V. What value of VAK is needed to trigger the device into
conduction?
1)
A)
+8.7 V
B)
–8.7 V
C)
+16.7 V
D)
Cannot be determined from the information given
Answer:
A
A)
B)
C)
D)
2)
An SCR is forced into forward conduction when VF exceeds the ________ rating of the device.
2)
A)
forward conducting voltage
B)
forward trigger voltage
C)
forward breakover voltage
D)
forward breakdown voltage
Answer:
C
A)
B)
C)
D)
3)
This is the symbol for a(n) ________.
3)
A)
SCS
B)
diac
C)
triac
D)
SCR
Answer:
A
A)
B)
C)
D)
4)
Thyristors are electronic devices that act as a ________.
4)
A)
silicon–controlled rectifier
B)
unijuction transistor
C)
silicon–controlled switch
D)
all of the above
Answer:
D
A)
B)
C)
D)
1
5)
Some of the popular applications of SCRs include ________.
5)
A)
GTO
choppers, inverters, and battery chargers
B)
relay control, time delay circuits, and regulated power supplies
C)
static switches, heater controls, and phase controls
D)
All of the above
Answer:
D
A)
B)
C)
D)
6)
Silicon was chosen for the construction of the SCR because of its ________.
6)
A)
switching speed characteristics
B)
temperature and power capabilities
C)
high frequency characteristic
D)
All of the above
Answer:
B
A)
B)
C)
D)
7)
The pnpn device that is of greatest interest today is the ________.
7)
A)
PUT
B)
SCR
C)
triac
D)
diac
Answer:
B
A)
B)
C)
D)
8)
Which of the following devices is actually an integrated circuit rather than a single discrete
component?
8)
A)
GTO device
B)
SIDAC
C)
triac
D)
optoisolator
Answer:
D
A)
B)
C)
D)
9)
This is the symbol for a(n) ________.
9)
A)
photocell
B)
LASCR
C)
optoisolator
D)
phototransistor
Answer:
B
A)
B)
C)
D)
2
10)
An SCR can be viewed as NPN aand PNP transitors connected ________ .
10)
A)
emitter to collector
B)
emitter to emitter
C)
emiter to base
D)
collector to base
Answer:
C, D
A)
B)
C)
D)
11)
Which of the following distinguishes the SCR from the SCS?
11)
A)
The SCS is driven into cutoff using entirely different methods.
B)
The SCS has a fourth terminal, called the anode gate.
C)
The SCS has less means of being forced into its forward conducting state.
D)
All of the above
Answer:
D
A)
B)
C)
D)
12)
This is the symbol for a(n) ________.
12)
A)
GTO
B)
Shockley diode
C)
PUT
D)
SCS
Answer:
C
A)
B)
C)
D)
13)
The silicon controlled switch has two ________.
13)
A)
gates
B)
anodes
C)
cathodes
D)
None of the above
Answer:
A
A)
B)
C)
D)
14)
The LASCR is a device that can be turned on by ________.
14)
A)
noise intensity of dB level
B)
wavelength of the light input
C)
light intensity
D)
harmonic content of the signal present at the gate
Answer:
C
A)
B)
C)
D)
3
15)
One region of the SCR curve when it is forward biased represents the non–conducting region of
operation. What is this region called?
15)
A)
forward non–conduction region
B)
forward turn–off region
C)
forward dropout region
D)
forward blocking region
Answer:
D
A)
B)
C)
D)
16)
UJTs are commonly used as ________.
16)
A)
tuned oscillators
B)
thyristor triggering devices
C)
amplifiers
D)
breakover devices
Answer:
B
A)
B)
C)
D)
17)
Which of the following devices acts as an SCR with IG= 0?
17)
A)
triac
B)
SBS
C)
Shockley diode
D)
GTO device
Answer:
C
A)
B)
C)
D)
18)
The ________ is commonly used to control SCR triggering.
18)
A)
JFET
B)
diac
C)
UJT
D)
SCR
Answer:
C
A)
B)
C)
D)
19)
The primary difference between the diac and the SCS is the fact that the ________.
19)
A)
SCS is capable of conducting in only one direction
B)
diac is no longer used in any practical application
C)
SCS requires the use of a snubber
D)
diac has a higher maximum power dissipation ratin
Answer:
A
A)
B)
C)
D)
4
20)
Which of the following devices can be driven into its conducting or nonconducting state by
applying the proper pulse to its gate terminal?
20)
A)
triac
B)
SBS
C)
GTO device
D)
Shockley diode
Answer:
C
A)
B)
C)
D)
21)
A triac is a ________ switching device.
21)
A)
trilateral
B)
unilateral
C)
multilateral
D)
bilateral
Answer:
D
A)
B)
C)
D)
22)
What are the two methods that are commonly used to return an SCR to its nonconducting state?
22)
A)
Anode current interruption and current holding
B)
Anode current interruption and forced commutation
C)
Current holding and forced commutation
D)
Forced commutation and current dropout
Answer:
B
A)
B)
C)
D)
23)
A silicon controlled switch (SCS) can be turned off by applying a(n) ________.
23)
A)
opposite–level pulse to the anode gate
B)
essential short–circuits from anode to cathode
C)
a low–level pulse on the cathode gate terminal
D)
All of the above
Answer:
D
A)
B)
C)
D)
24)
The forward operating curve of the SCR is identical to that of a ________.
24)
A)
SCS
B)
triac
C)
GTO
D)
diac
Answer:
A
A)
B)
C)
D)
5
25)
This is the symbol for a(n) ________.
25)
A)
SCR
B)
triac
C)
diac
D)
SCS
Answer:
A
A)
B)
C)
D)
26)
This is the symbol for a(n) ________.
26)
A)
UJT
B)
FET
C)
BJT
D)
SCS
Answer:
A
A)
B)
C)
D)
27)
One of the very important characteristics of the GTO is ________.
27)
A)
improved turn–off time
B)
improved noise characteristics
C)
improved blocking region characteristics
D)
improved current handling characteristics
Answer:
A
A)
B)
C)
D)
28)
The region of the SCR forward operating curve that represents the nonconducting region of
operation is called the ________.
28)
A)
forward off–state region
B)
forward dropout region
C)
forward blocking region
D)
None of the above
Answer:
C
A)
B)
C)
D)
6
29)
Once an SCR is forced into forward conduction, it continues to conduct until IF drops below the
________ rating of the device.
29)
A)
minimum forward current
B)
dropout current
C)
holding current
D)
forward breakover current
Answer:
C
A)
B)
C)
D)
30)
This is the symbol for a(n) ________.
30)
A)
UJT
B)
GTO
C)
diac
D)
triac
Answer:
D
A)
B)
C)
D)
31)
This is the symbol for a(n) ________.
31)
A)
LASCR
B)
GTO
C)
Darlington transistor
D)
triac
Answer:
B
A)
B)
C)
D)
32)
This is the symbol for a(n) ________.
32)
A)
GTO
B)
SCR
C)
triac
D)
diac
Answer:
D
A)
B)
C)
D)
7
33)
Thyristors are electronic devices that act as a ________.
33)
A)
unijunction transistor
B)
gate turn–off switch
C)
silicon controlled rectifier
D)
All of the above
Answer:
D
A)
B)
C)
D)
34)
Anode–current interruption and forced commutation are the two methods that are used to
________ an SCR.
34)
A)
turn on
B)
hold on
C)
turn off
D)
None of the above
Answer:
C
A)
B)
C)
D)
35)
A UJT has the following values: = 0.72 (maximum) and VBB = 12 V. What is the maximum value
of VRB1 required to trigger the device into conduct ion?
35)
A)
12 V
B)
8.64 V
C)
17.4 V
D)
9.34 V
Answer:
B
A)
B)
C)
D)
36)
This is the symbol for a(n) ________.
36)
A)
Shockley diode
B)
SCS
C)
GTO
D)
UJT
Answer:
A
A)
B)
C)
D)
37)
The LASCR is a device whose state is controlled by ________.
37)
A)
spectral wavelength
B)
the light–area product
C)
light amplitude
D)
light intensity
Answer:
D
A)
B)
C)
D)
8
Answer Key
Testname: C17
1)
A
2)
C
3)
A
4)
D
5)
D
6)
B
7)
B
8)
D
9)
B
10)
C, D
11)
D
12)
C
13)
A
14)
C
15)
D
16)
B
17)
C
18)
C
19)
A
20)
C
21)
D
22)
B
23)
D
24)
A
25)
A
26)
A
27)
A
28)
C
29)
C
30)
D
31)
B
32)
D
33)
D
34)
C
35)
B
36)
A
37)
D