PNPN
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PNPN 1 1. The peak and valley currents of the PUT are typically ________ those of a similarly rated UJT. A. lower than B. the same as C. higher than D. None of the above Answer: Option A 2. The ________ the anode gate current, the ________ the required anode-to-cathode voltage to turn the SCS device on. A. higher, higher B. lower, lower C. higher, lower D. None of the above Answer: Option C 3. SCRs have been designed to control powers as high as ________, with individual ratings as high as ________ at ________. A. 1800 MW, 10 A, 2000 V B. 1800 MW, 2000 A, 10 V C. 10 MW, 2000 A, 1800 V D. 2000 MW, 10 A, 1800 V Answer: Option C 4. The two-layer semiconductor diode has led to ________layer devices. A. three- B. four- C. five- D. All of the above Answer: Option D 5. The minimum operating voltage of the UJT is typically ________ that of a similarly rated PUT. A. lower than
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PNPN 1
1. The peak and valley currents of the PUT are typically ________ those of a similarly rated UJT. A. lower than B. the same as C. higher than D. None of the above
Answer: Option A
2. The ________ the anode gate current, the ________ the required anode-to-cathode voltage to turn the SCS device on. A. higher, higher B. lower, lower C. higher, lower D. None of the above Answer: Option C
3. SCRs have been designed to control powers as high as ________, with individual ratings as high as ________ at ________. A. 1800 MW, 10 A, 2000 V B. 1800 MW, 2000 A, 10 V C. 10 MW, 2000 A, 1800 V D. 2000 MW, 10 A, 1800 V
Answer: Option C
4. The two-layer semiconductor diode has led to ________layer devices. A. three- B. four- C. five- D. All of the above Answer: Option D 5. The minimum operating voltage of the UJT is typically ________ that of a similarly rated
PUT. A. lower than
B. the same as C. higher than
D.
None of the above
Answer: Option C
6. How many terminals does a programmable unijunction transistor (PUT) have? A. 4 B. 3 C. 2 D. 1
Answer: Option B 7. What is the typical value of the reverse resistance of SCRs?
A.
1 to 10
B.
100 to 1 k
C.
1 k to 50 k
D.
100 k or more
Answer: Option D 8. The ISO-LIT Q1 16-pin Litronixopto-isolator DIP contains ________ opto-isolators.
A. 4 B. 8 C. 12 D. 6
Answer: Option A 9. How many terminals does a Shockley diode have?
A. 5 B. 4 C. 3 D. 2 Answer: Option D
10. What is the range of the variable resistor in the equivalent circuit of a unijunction
transistor?
A.
50 to 5 k
B.
6 k to 10 k
C.
5 to 50
D.
1 to 5
Answer: Option A 11. Which one of the SCR terminals fires the SCR?
A. Anode B. Cathode C. Gate D. All of the above
Answer: Option C 12. Which of the following devices has the smallest turn-off time?
A. SCR B. GTO C. SCS D. LASCR
Answer: Option B 13. What is the range of the turn-on times in high-power SCR devices?
A.
30 s to 100 s
B.
10 s to 25 s
C.
5 s to 8 s
D.
1 s to 5 s
Answer: Option B 14. What is the frequency range of application of SCRs?
A. About 10 kHz B. About 50 kHz C. About 250 kHz D. About 1 mHz
Answer: Option B
15. This symbol is an example of a(n) ________.
A. SCR B. SCS C. GTO D. diac
Answer: Option C 16. Which of the following devices has nearly the same turn-on time as turn-off time?
A. SCR B. GTO C. SCS D. LASCR
Answer: Option B 17. This symbol is an example of a(n) ________.
A. SCR B. SCS C. GTO D. DIAC
Answer: Option A 18. Which of the transistors of an SCR are conducting when the SCR is fired and is in the
conduction mode? A. npn B. pnp C. Both npnand pnp D. Neither npn nor pnp
Answer: Option C 19. For an SCS, a ________ pulse at the anode gate turns the device on, while a ________
pulse will turn it off. A. negative, positive B. positive, negative
Answer: Option A 20. An advantage of the SCR over the SCS is the reduced turn-off time.
A. True B. False
Answer: Option B 21. This is an example of a high-isolation ________ gate.
A. OR B. NOT C. AND D. NAND
Answer: Option C 22. Which of the following devices has (have) four layers of semiconductor materials?
A. Silicon-controlled switch (SCS) B. Gate turn-off switch (GTO) C. Light-activated silicon-controlled rectifier (LASCR) D. All of the above
Answer: Option D 23. Which of the following parameters are usually provided by the manufacturer on the
specification sheet for SCRs? A. Turn-on time (ton ) B. Turn-off time (toff ) C. Junction and case temperatures (tj and tc ) D. All of the above
Answer: Option D 24. What is the maximum current (rms) rating for commercially available LASCRs today?
A. 3 A B. 15 A C. 20 A D. 25 A
Answer: Option A 25. Which of the following areas is (are) applications of an SCS?
A. Counters B. Pulse generators C. Voltage sensors D. All of the above
Answer: Option D
26. This symbol is an example of a(n) ________.
A. SCR B. SCS C. GTO D. DIAC Answer: Option D
27. How many terminals does a silicon-controlled switch (SCS) device have?
A. 2 B. 3 C. 4 D. 5
Answer: Option C 28. What is the typical value of the triggering anode gate for SCS devices?
A. 1.5 mA B. 150 A C. 15 A D. 1 A
Answer: Option A 29. What is the typical range of turn-off times for SCRs?
A.
5 s to 30 s
B.
1 s to 5 s
C.
0.1 s to 1 s
D.
0.01 s to 0.1 s
Answer: Option A 30. Which of the following is (are) the advantages of the SCS over a corresponding SCR?
A. Reduced turn-off time B. Increased control and triggering sensitivity C. More predictable firing situation D. All of the above
Answer: Option D
31. This symbol is an example of a(n)________.
A. SCR B. SCS C. GTO D. DIAC Answer: Option B
32. Which of the following transistors is an SCR composed of?
A. npn, pnp B. npn, npn C. pnp, pnp D. None of the above
Answer: Option A 33. A thyristor is a ________-layer semiconductor material device.
A. 2 B. 3 C. 4 D. 5 Answer: Option C
34. How many layers of semiconductor materials does a silicon-controlled rectifier (SCR)
have? A. 2 B. 3 C. 4 D. 5
Answer: Option C
PNPN 2
1. Which of the following devices does not have a cathode terminal? A. SCR B. SCS C. Triac D. Shockley diode Answer: Option C
2. Today, the SCR is more widely used than the TRIAC. A. True B. False
Answer: Option B
3. Which of the following devices is unquestionably of the greatest interest today? A. SCR B. GTO C. LASCR D. SCS Answer: Option A 4. Which of the following devices has a negative-resistance region in its characteristics curve? A. SCR B. SCS C. Unijunction transistor D. Phototransistor Answer: Option C
5. Determine RB1 for a silicon PUT if it is determined that h = 0.84, VP = 11.2 V, and RB2 = 5
k .
A.
12.65 k
B.
16.25 k
C.
20.00 k
D.
26.25 k
Answer: Option D
6. In general, the triggering (turn-on) anode gate current is ________ the required cathode gate current. A. larger than
B. the same as
C. smaller than
D. None of the above
Answer: Option A
7. The four-layer devices with a control mechanism are commonly referred to as ________. A. thyristors
B. transistors
C. diodes
D. None of the above
Answer: Option A
8. ________ is(are) example(s) of applications of phototransistors. A. Punch-card readers
B. Lighting control (for example, on highways)
C. Level indication
D. All of the above
Answer: Option D
9. ________ in light intensity corresponds with ________ in collector current. A. An increase, an increase
B. An increase, a decrease
C. A decrease, an increase
D. None of the above
Answer: Option A
10. A(n) ________ can be triggered in either direction. A. SCR
B. Shockley diode
C. diac
D. SCS
Answer: Option C
11. At –65ºC the minimum current that will trigger the series of an SCR is ________, while at +150ºC only ________ is required.
A. 20 mA, 100 mA B. 50 mA, 75 mA C. 75 mA, 50 mA D. 100 mA, 20 mA
Answer: Option D
12. The current induced by photoelectric effects is the ________ current of the transistor. A. collector B. base C. emitter D. None of the above
Answer: Option B
13. The switching time of an opto-isolator ________ with increased current, while for many devices it is exactly the reverse. A. increases B. decreases C. remains the same D. None of the above
Answer: Option B
14. The________ are the terminals of SCRs. A. anode and cathode B. anode, gate, and cathode C. base, anode, and cathode D. gate and anode Answer: Option B
15. An opto-isolator contains ________. A. an infrared LED B. a photodetector C. both an infrared LED and a photodetector D. None of the above
Answer: Option C
16. The method(s) for turning off an SCR is (are) categorized as ________. A. current interruption B. forced commutation C. both current interruption and forced commutation D. None of the above
Answer: Option C
17. In a programmable unijunction transistor (PUT), the ________ can be controlled through a couple of resistors and the supply voltage. A. interbase resistance RBB B. intrinsic stand-off ratio C. emitter firing potential VP D. All of the above
Answer: Option D
18. The ________ are the terminals of an SCS. A. anode, anode gate, cathode gate, and cathode B. anode, cathode, cathode gate, and gate C. anode, anode gate, cathode, and gate
D.
anode, cathode, and gate
Answer: Option A
19. The SCRs have typical turn-on times of ________ in the regeneration action. A. 0.1 μs to 1 μs B. 0.1 ms to 1 ms C. 3 ms to 5 ms D. 5 ms to 9 ms Answer: Option A
20. In the conduction region, the dynamic resistance of the SCR is typically ________ to ________.
A.
0.01 , 0.1
B.
1 , 10
C.
50 , 100
D. 500 , 10 k
Answer: Option A
21. The anode gate connection can be used to turn the SCS device ________. A. on
B. off
C. neither on nor off
D. either on or off
Answer: Option D
22. ________ is (are) the element(s) of a unijunction transistor's equivalent circuit. A. One fixed resistor
B. A variable resistor
C. A diode
D. All of the above
Answer: Option D
23. To turn on an SCS device, a ________ pulse must be applied to the anode gate terminal; to turn off the device, a ________ pulse is required. A. positive, positive
B. negative, positive
C. positive, negative
D. negative, negative
Answer: Option B
24. In a half-wave variable-resistance phase control operation, the control cannot be extended past a ________ phase displacement. A. 45º B. 90º
C. 135º D. 180º
Answer: Option B
25. ________ are areas of application for SCRs. A. Relay controls
B. Time-delay circuits
C. Motor controls
D. All of the above
Answer: Option D
