Online Questions and Answers Topic Outline
- MCQs in Introduction to Other Two-Terminal Devices | MCQs in Schottky Barrier (Hot-Carrier) Diodes | MCQs in Varactor (Varicap0 Diodes | MCQs in Power Diodes | MCQs in Tunnel Diodes | MCQs in Photodiodes | MCQs in Photoconductive Cells | MCQs in IR Emitters | MCQs in Liquid-Crystal Displays (LCD) | MCQs in Solar Cells | MCQs in Thermistors
Practice Exam Test Questions
Choose the letter of the best answer in each questions.
1. Which of the following is (are) diodes?
- A. Schottky
- B. Varactor
- C. Tunnel
- D. All of the above
2. Which of the following metals is (are) used in the fabrication of Schottky diodes?
- A. Molybdenum
- B. Platinum
- C. Tungsten
- D. All of the above
3. What are the typical ranges of reverse-bias current levels IS for low-power and high-power Schottky diodes at room temperature?
- A. Picoamperes, nanoamperes
- B. Nanoamperes, microamperes
- C. Microamperes, milliamperes
- D. Milliamperes, amperes
4. What is the voltage drop across Schottky diodes?
- A. 0 V to 0.2 V
- B. 0.7 V to 0.8 V
- C. 0.8 V to 1.0 V
- D. 1.0 V to 1.5 V
5. What metal(s) is(are) used in the construction of Schottky diodes?
- A. Molybdenum
- B. Platinum
- C. Tungsten
- D. Silicon
- E. Any of the above
6. For a 50-A unit, the PIV of the Schottky is about _____ compared to 150 V for the p-n junction variety.
- A. 25
- B 50
- C. 75
- D. 100
7. Schottky diodes are very effective at frequencies approaching _____.
- A. 20 GHz
- B. 10 MHz
- C. 100 MHz
- D. 1 MHz
8. This is an approximate equivalent circuit for the _____ diode.
- A. Schottky
- B. varicap
- C. tunnel
9. What is the range of the varying capacitor CT in varactor diodes?
- A. 0 pF to 5 pF
- B. 2 pF to 100 µF
- C. 2 µF to 100 µF
- D. 2 pF to 100 pF
10. Which of the following areas is (are) applications of varactor diodes?
- A. FM modulators
- B. Automatic-frequency control devices
- C. Adjustable bandpass filters
- D. All of the above
11. The tuning diode is a _____-dependent, variable _____.
- A. voltage, resistor
- B. current, capacitor
- C. voltage, capacitor
- D. current, inductor
12. This is an equivalent circuit for the _____ diode.
- A. Schottky
- B. varicap
- C. tunnel
13. The varicap diode has a transition capacitance sensitive to the applied reverse-bias potential that is a maximum at zero volts and decreases _____ with increasing reverse-bias potentials.
- A. logarithmically
- B. parabolically
- C. exponentially
14. The majority of power diodes are constructed using _____.
- A. molybdenum
- B. platinum
- C. tungsten
- D. silicon
15. The current capability of power diodes can be increased by placing two or more in series.
- A. True
- B. False
16. The PIV rating of power diodes can be increased by stacking the diodes in series.
- A. True
- B. False
17. Which of the following diodes has a negative-resistance region?
- A. Schottky
- B. Varactor
- C. Tunnel
- D. Power
18. Which of the following semiconductor materials is (are) used in the manufacturing of tunnel diodes?
- A. Germanium
- B. Gallium
- C. Both germanium and gallium arsenide
- D. Silicon
19. What is the ratio IP / IV for gallium arsenide?
- A. 1:1
- B. 5:1
- C. 10:1
- D. 20:1
20. What is the limit of peak current IP in tunnel diodes?
- A. A few microamperes to several hundred amperes
- B. A few microamperes to several amperes
- C. A few microamperes to several milliamperes
- D. A few microamperes to several hundred microamperes
21. What is the maximum peak voltage for tunnel diodes?
- A. 50 mV
- B. 100 mV
- C. 250 mV
- D. 600 mV
22. In which region is the operating point stable in tunnel diodes?
- A. Negative-resistance
- B. Positive-resistance
- C. Both negative- and positive-resistance
- D. Neither negative- nor positive-resistance
23. Which of the following diodes is limited to the reverse-bias region in its region of operation?
- A. Schottky
- B. Tunnel
- C. Photodiode
- D. Rectifier
24. What is the response time of cadmium sulfide (CdS) in photoconductive cells?
- A. 100 ms
- B. 50 ms
- C. 25 ms
- D. 10 ms
25. Which of the following areas is (are) an application of infrared-emitting diodes?
- A. Intrusion alarms
- B. Shaft encoders
- C. Paper-tape readers
- D. All of the above
26. What is the maximum temperature limit for liquid-crystal displays (LCDs)?
- A. 10ºC
- B. 30ºC
- C. 60ºC
- D. 100ºC
27. What is the response time of light-emitting diodes (LEDs)?
- A. Less than 100 ns
- B. 50 ms
- C. 100 ms to 300 ms
- D. 400 ms
28. What is the response time of LCDs?
- A. Less than 100 ns
- B. 50 ms
- C. 100 ms to 300 ms
- D. 400 ms
29. What is the power density received from the sun at sea level?
- A. 10 mW/cm2
- B. 100 mW/cm2
- C. 500 mW/cm2
- D. 1 W/cm2
30. Which of the following semiconductor materials is (are) used for manufacturing solar cells?
- A. Gallium arsenide
- B. Indium arsenide
- C. Cadmium sulfide
- D. All of the above
31. What type of temperature coefficient do thermistors have?
- A. Positive
- B. Negative
- C. Either positive or negative
- D. None of the above
32. Which of the following materials is (are) used in the manufacturing of thermistors?
- A. Ge
- B. Si
- C. A mixture of oxides of cobalt, nickel, strontium, or manganese
- D. All of the above
33. What is the resistance of thermistors at room temperature (20ºC)?
- A. 5 kΩ
- B. 1 kΩ
- C. 100 Ω
- D. 1 Ω
34. What is the resistance of thermistors at boiling temperature (100ºC)?
- A. 5 kΩ
- B. 1 kΩ
- C. 100 Ω
- D. 1 Ω
35. What is the typical level of change in resistance per degree change in temperature?
- A. 1% to 2%
- B. 3% to 5%
- C. 7% to 10%
- D. 10% to 25%
FILL-IN-THE-BLANKS
1. Schottky diodes have _____.
- A. quick response time
- B. a lower noise figure
- C. both quick response time and a lower noise figure
- D. None of the above
2. Schottky diode construction results in a _____ uniform junction region and a _____ level of ruggedness.
- A. more, high
- B. less, high
- C. more, low
- D. less, low
3. In both n-type and p-type silicon materials, the _____ is the majority carrier in a Schottky diode.
- A. hole
- B. electron
- C. proton
- C. neutron
4. The barrier at the junction for a Schottky diode is _____ that of the p-n junction device in both the forward- and reverse-bias regions.
- A. the same as
- B. more than
- C. less than
- D. None of the above
5. A Schottky diode has _____ level of current at the same applied bias compared to that of the p-n junction at both the forward- and reverse-bias regions.
- A. a lower
- B. a higher
- C. the same
- D. None of the above
6. The PIV of Schottky diodes is usually _____ that of a comparable p-n junction unit.
- A. 1/2
- B. 1/3
- C. 1/4
- D. 1/5
7. Varactor diodes are _____.
- A. semiconductor devices
- B. voltage-dependent
- C. variable capacitors
- D. All of the above
8. In varactor diodes, as the reverse-bias potential increases, the width of the depletion region _____, which in turn _____ the transition capacitance.
- A. increases, increases
- B. decreases, reduces
- C. increases, reduces
- D. decreases, increases
9. The normal range of reverse-bias voltage VR for varactor diodes is limited to about _____.
- A. 15 V
- B. 20 V
- C. 25 V
- D. 40 V
10. In the reverse-bias region of varactor diodes, the resistance RR in parallel with the varying capacitor is _____ and the series resistance RS is _____.
- A. very large, very small
- B. very large, very large
- C. very small, very large
- D. very small, very small
11. The majority of power diodes are constructed using silicon because of its higher _____ rating(s).
- A. current
- B. temperature
- C. PIV
- D. All of the above
12. The current capability of power diodes can be increased by placing two or more of the diodes in _____, and the PIV rating can be increased by stacking the diodes in _____.
- A. parallel, parallel
- B. series, parallel
- C. parallel, series
- D. series, series
13. In the negative-resistance region of tunnel diodes, as the terminal voltage increases, the diode current _____.
- A. remains the same
- B. decreases
- C. increases
- D. is undefined
14. The p-n junction of a tunnel diode is doped at a level from _____ to _____ times that of a typical semiconductor diode.
- A. one, several
- B. several, ten
- C. more than ten, several hundred
- D. one hundred, several thousand
15. The negative-resistance region of tunnel diodes can be used in the design of _____.
- A. oscillators
- B. switching networks
- C. pulse generators
- D. All of the above
16. The wavelength is usually measured in _____.
- A. angstrom units
- B. micrometers
- C. both angstrom units and micrometers
- D. None of the above
17. In photodiodes, an increase in light intensity _____ the reverse current.
- A. increases
- B. decreases
- C. maintains
- D. None of the above
18. Ge has a _____ dark current and a _____ level of reverse current than silicon.
- A. higher, lower
- B. higher, higher
- C. lower, higher
- D. lower, lower
19. The response time for cadmium selenide (CdSe) is _____.
- A. 100 ms
- B. 50 ms
- C. 25 ms
- D. 10 ms
20. A decrease in illumination _____ the resistance Rλ of a photoconductive cell.
- A. decreases
- B. increases
- C. maintains
- D. None of the above
21. LCDs have _____ power requirement than (as) LEDs.
- A. a lower
- B. a higher
- C. the same
- D. None of the above
22. LCDs are characteristically _____ LEDs.
- A. the same speed as
- B. much slower than
- C. faster than
- D. much faster than
23. _____ is (are) the most widely used material(s) for solar cells.
- A. Selenium
- B. Silicon
- C. Both selenium and silicon
- D. Cadmium sulfide
24. In general, silicon _____.
- A. has a higher conversion efficiency
- B. has greater stability
- C. is less subject to fatigue
- D. All of the above
25. Typical levels of efficiency for solar cells range from _____ to _____.
- A. 10%, 40%
- B. 40%, 50%
- C. 50%, 75%
- D. 75%, 100%
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