Source text. Published from the recorded source PDF for NEETS Module 7: Solid-State Devices and Power Supplies.
INDEX-1
Module 7 Index
A Amplifier classes of operation, 2-21 class A, 2-21 class AB, 2-22 class B, 2-22 class C, 2-22 Applications, semiconductor, 1-3 Atomic structure, semiconductor theory, 1-5 B Bias, types of, basic transistor amplifier, 2-18 base current (fixed bias), 2-19 combination, 2-20 self-bias, 2-19 Bridge rectifier, 4-10 C Capacitor filter, 4-12 Classification, transistor fundamentals, 2-2 Combination bias, 2-20 Competition, semiconductor, 1-4 Conduction process, semiconductor theory, 1-12 Configurations, transistor, 2-23 common base, 2-26 common collector, 2-27 common emitter, 2-24 Construction, semiconductor diode, 1-16 Construction, transistor fundamentals, 2-4 Conventional full-wave rectifier, 4-3 Covalent bonding, semiconductor theory, 1-10 Current regulators, 4-35 D Diode identification, signal diodes, 1-29 Diode maintenance, signal diodes, 1-31 Diode, semiconductor, 1-15 construction, 1-16 diode characteristics, 1-27 PN junction application, 1-23 Diode, semiconductor—Continued PN junction operation, 1-18 Diodes, 3-2 optoelectronic devices, 3-27 silicon controlled rectifier (SCR), 3-18
Triac, 3-24
tunnel, 3-8 varactor, 3-15 Zener, 3-2 Doping process, semiconductor, 1-13 N-type semiconductor, 1-14 P-type semiconductor, 1-14 E Energy bands, semiconductor theory, 1-8 F FET, field-effect transistors, 3-38 Filters, power supply, 4-12 capacitor, 4-17 LC capacitor-input, 4-32 LC choke-input, 4-22 resistor-capacitor (RC), 4-30 Fixed bias, 2-19 G Glossary, AI-1 H Half-wave rectifier, 1-23 I Identification, transistor, 2-27 L LC capacitor-input filter, 4-32 INDEX-2 LC choke-input filter, 4-22 Load regulation, 4-34 M Maintenance, transistor, 2-31 lead identification, 2-32 precautions, 2-31 transistor testing, 2-33 Microelectronics, 2-37 N NPN transistor operation, 2-6 O Optoelectronic devices, 3-27 P Periodic table of the elements, AII-1 PN junction application, 1-23 diode switch, 1-26 half-wave rectifier, 1-23 PN junction operation, semiconductor diode, 1-15 current flow in the N-type material, 1-18 current flow in the P-type material, 1-18 junction barrier, 1-19 PNP transistor operation, 2-11 Power transformer, 4-3 Practical full-wave rectifier, 4-8 R Rectifier, 4-4 bridge, 4-10 conventional full-wave, 4-7 half-wave, 4-4 practical full-wave, 4-8 ripple frequency, 4-6 rms, peak, and average values, 4-5 Rectifier diodes, 1-28 Regulators, power supply, 4-35 current, 4-43 Regulators, power supply—Continued series and shunt voltage regulators, 4-36 Resistor-capacitor (RC) filters, 4-30 Ripple frequency, 4-6 S SCR, silicon controlled rectifier, 3-18 Self-bias, 2-19 Semiconductor diodes, 1-1 diode identification, 1-29 diode maintenance, 1-31 introduction to solid-state devices, 1-1 rectifier diodes, 1-28 semiconductor applications, 1-3 semiconductor competition, 1-4 semiconductor development, 1-2 semiconductor theory, 1-5 signal diodes, 1-28 summary 1-34 Series and shunt voltage regulators, 4-36 Solid-state devices, introduction to, 1-1 Solid-state power supplies, 4-1 basic power supply, 4-1 troubleshooting, 4-51 Special devices, 3-1 Specifications, transistor, 2-29 T Theory, semiconductor, 1-5 atomic structure, 1-5 conduction process, 1-12 covalent bonding, 1-10 doping process, 1-13 energy bands, 1-8 Transistors, 2-1 basic transistor amplifier, 2-15 FET (field effect), 3-38 fundamentals, 2-2 identification, 2-30 introduction to, 2-1 maintenance, 2-31 microelectronics, 2-37 specifications, 2-29 UJT (unijunction), 3-34 INDEX-3
Triac, 3-22
Troubleshooting power supplies, 4-51 testing, 4-49 Tunnel diode, 3-8 U UJT, unijunction transistor, 3-34 V Varactor, 3-15 Voltage multipliers, power supply, 4-45 short circuit protection, 4-50 Voltage regulation, power supply, 4-34 Z Zener diodes, 3-2 Assignment Questions Information: The text pages that you are to study are provided at the beginning of the assignment questions. 1
Assignment 1
Textbook assignment: Chapter 1, “Semiconductor Diodes,” pages 1-1 through 1-47. _________________________________________________________________________________ 1-1. Which of the following electronic devices operates by virtue of the movement of electrons within a solid piece of semiconductor material? 1. Transistor 2. Junction diode 3. Solid-state device 4. Each of the above 1-2. Which of the following electronic devices is a minute piece of semiconductor material that can produce complete electronic circuit functions?
1. Zener diode 2. Light-emitting diode 3. Integrated circuit 4. Field effect transistor 1-3. Which of the following terms is used for the decrease in resistance as the temperature of the semiconductor increases? 1. Positive temperature coefficient 2. Negative temperature coefficient 3. Faraday temperature coefficient 4. Zero temperature coefficient 1-4. In addition to rectifying properties, selenium has the property of being light sensitive. How is selenium's resistance affected by light? 1. It decreases with an increase in light intensity 2. It increases with an increase in light intensity 3. It remains constant with variation in light intensity 4. It increases regardless of the variation in light intensity 1-5. One of the most sensitive elements of semiconductor materials is galena. Galena is a crystalline form of what material?
1. Krypton 2. Bismuth 3. Strontium 4. Lead sulfide 1-6. What significant discovery caused a breakthrough in the development of semiconductor devices? 1. The junction diode 2. The junction barrier 3. The extrinsic semiconductor 4. The point-contact transistor 1-7. Which of the following devices is frequently used to regulate power supply voltages at precise levels? 1. Junction diode 2. Tunnel diode 3. Esaki diode 4. Zener diode 1-8. Which of the following solid-state devices has both gain and fast-switching capabilities?
1. Zener diode 2. Tunnel diode 3. Junction diode 4. Point-contact diode 1-9. Which of the following advantages, if any, does a conventional electron tube have over a semiconductor device? 1. It is more efficient 2. It has a longer life 3. It is more economical 4. None of the above 2 1-10. When compared to an electron tube, the semiconductor device has which of the following limitations? 1. The semiconductor is more sensitive to temperature 2. The semiconductor is used only in radar equipment 3. The semiconductor is difficult to adapt to commercial products 4. Each of the above 1-11. Matter can be found in which of the following forms?
1. Solid 2. Liquid 3. Gas 4. Each of the above 1-12. A substance that cannot be reduced to a simpler form by chemical means is called a/an 1. element 2. mixture 3. compound 4. solution 1-13. An atom is the smallest possible particle that retains the characteristics of which of the following substances? 1. An element 2. A mixture 3. A compound 4. A solution 1-14. A molecule is the smallest possible particle that retains the characteristics of which of the following substances? 1. An element 2. A mixture 3. A compound 4. A solution 1-15. Which part of the atom has a negative charge and a small mass?
1. Proton 2. Electron 3. Positron 4. Neutron 1-16. Which part of the atom has a positive charge and a large mass? 1. Proton 2. Electron 3. Positron 4. Neutron 1-17. Which part of the atom has no electrical charge? 1. Proton 2. Electron 3. Positron 4. Neutron 1-18. What name is given to the outermost shell of an atom? 1. First shell 2. M shell 3. Valence shell 4. Subshell 1-19. What term is used to describe an atom which has more than its normal amount of electrons? 1. Ion 2. Ionization 3. Positive ion 4. Negative ion 1-20. Which of the following terms is defined as the process by which an atom gains or loses electrons?
1. Quanta 2. Ionization 3. Loss of energy 4. Remaining energy 3 1-21. Electrons are NEVER found in which of the following bands? 1. Energy band 2. Valence band 3. Forbidden band 4. Conduction band 1-22. What determines whether a substance is an insulator, semi-conductor, or conductor? 1. The separation between the valence and forbidden bands 2. The separation between the conduction and valence bands 3. The separation between the conduction and forbidden bands 4. The separation between the forbidden band and the energy gap Figure 1A.—Energy level diagram.
In Answering Questions 1-23 And 1-24,
Refer To Figure 1-A.
1-23. What energy level in figure 1-A is classified as the best insulator? 1. A 2. B 3. C 4. D
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1-24. When the insulator is compared to the semiconductor, (a) which one requires the least energy to move an electron and (b) from which point in the energy level in figure 1-A does the electron leave in its travel to the conduction band? 1. (a) Semiconductor (b) Valence band 2. (a) Insulator (b) Valence band 3. (a) Semiconductor (b) Forbidden band 4. (a) Insulator (b) Forbidden band 1-25. Which of the following terms applies to the process that holds the atom together in a crystal? 1. Suhl effect 2. Superposition 3. Boundary defect 4. Covalent bonding 1-26. The movement of electrons in a semiconductor toward the applied voltage is termed 1. hole flow 2. positive conduction 3. negative conduction 4. electron current flow 1-27. When the theory of semiconductors is discussed, what term(s) is/are used to describe the current that flows in the semiconductor?
1. Hole flow 2. Electron flow 3. Both 1 and 2 above 4. Electromotive flow 1-28. What process takes place within the semiconductor to cause hole flow? 1. The breaking of covalent bonds 2. The combining of valence bands 3. The flexing of the material 4. The splitting of atoms 4 1-29. A material which has an equal number of electron-hole pairs and conducting electrons is known as what type of semiconductor material? 1. Extrinsic 2. Intrinsic 3. N-type 4. P-type 1-30. The process of adding impurities to crystals is known by which of the following terms?
1. Charging 2. Doping 3. Honing 4. Processing 1-31. When doping increases the number of free electrons in a semiconductor, what type of impurity has been added? 1. E-type 2. N-type 3. O-type 4. P-type 1-32. The semiconductor doping impurities— arsenic, antimony, and bismuth—are classified as what type of impurities? 1. Active 2. Neutral 3. Trivalent 4. Pentavalent 1-33. In the P-type semiconductor, what are the majority carriers? 1. The electrons 2. The holes 3. The inactive atoms 4. The inert atoms 1-34. What is/are the purpose(s) of the PN junction diode?
1. To rectify only 2. To amplify only 3. To rectify and amplify 4. To switch 1-35. In a schematic diagram of a PN junction diode, which of the following symbols represents the cathode (N-type material)? 1. The arrow 2. The circle 3. The vertical bar 4. The horizontal line 1-36. Which of the following alphanumerical codes correctly identifies the diode, crystal rectifier number 3, in a circuit? 1. CR3 2. DR3 3. RD3 4. CRD3 1-37. Which of the following is the schematic symbol of the PN junction diode? 1. 3. 2. 4 1-38. The placing of an impurity on a semiconductor of the opposite impurity and fusing the two together produce what type of semiconductor junction?
1. Grown junction 2. Alloy Junction 3. Barrier junction 4. Intrinsic junction 5 1-39. A perfect bond at the junction of the two diode materials is important for which of the following reasons? 1. It is the point at which rectification takes place 2. It is the point at which amplification takes place 3. It is the main structural point from where the diode gets its strength 4. All of the above 1-40. Current flow in a copper wire can be compared to current flow in what type(s) of semiconductor material? 1. N-type only 2. P-type only 3. N- and P-type 4. All types 1-41. What is the overall electrical charge of the N-material in a semiconductor?
1. Zero 2. Some negative value 3. Some positive value 4. Depending upon the balance of electrons, it will be positive or negative 1-42. What is the overall electrical charge of the P-material in a semiconductor? 1. Zero 2. Some negative value 3. Some positive value 4. Depending upon the balance of electrons, it will be positive or negative 1-43. What causes the process called junction recombination to occur when N and P materials are joined together? 1. The diffusion of electrons and holes moving across the junction into the two materials 2. The generation of heat which causes the electrons to bombard the holes at the junction 3. The development of an electrostatic field on each side of the junction 4. The loss of electrons to the depletion region 1-44. After the junction recombination process has reached equilibrium, what is the area that surrounds the junction called?
1. The anode 2. The free ion space 3. The depletion region 4. The electrostatic field 1-45. A voltage applied to a PN junction so that it reduces the junction barrier and aids current flow is what type of bias? 1. Indirect 2. Reverse 3. Forward 4. Direct 1-46. In a forward-biased PN junction, when an electron leaves the negative terminal of the battery and enters the N material, it becomes what type of carrier? 1. Loop 2. Signal 3. Majority 4. Minority 6 1-47. Which of the following illustrations depicts a properly forward-biased PN junction?
(Note: The number of elements in the battery indicates the applied voltages.) 1. 2. 3. 4. 1-48. In the PN junction, which of the following actions will increase the number of majority carriers and increase current flow in a forward-biased condition? 1. Increasing the size of the P material 2. Decreasing the size of the P material 3. Increasing battery voltage 4. Decreasing battery voltage 1-49. A voltage applied to a PN junction so that it will increase the junction barrier and offer a high resistance to current flow is called what type of bias?
1. Direct 2. Forward 3. Reverse 4. Indirect 1-50. When the negative terminal of a battery is connected to the P material, and the positive terminal is connected to the N material, what type of bias is being used? 1. Self 2. Forward 3. Reverse 4. Inverse 1-51. What provides you with information concerning the voltage-current relationship of a PN junction diode? 1. The body color of the diode 2. The color coded bands on the diode 3. The printed information on the diode 4. The characteristic curve graph of the diode
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7 Figure 1B.—An electronic circuit.
In Answering Questions 1-52 Through
1-55, REFER TO FIGURE 1-B. 1-52. What type of circuit is shown in figure 1-B? 1. Full-wave rectifier 2. Half-wave rectifier 3. Clipper 4. Clamper 1-53. With the input shown, which of the following outputs would be correct? 1. 2. 3. 4. 1-54. Which of the following outputs would be correct with two alternations of the ac input signal applied? 1. 2. 3. 4. 1-55. What is/are the purposes(s) of RL? 1. It limits the amount of current flow in the circuit 2. It develops the output signal 3. Both 1 and 2 above 4. It maintains the proper bias on the diode
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8 Figure 1C
In Answering Questions 1-56 And 1-57,
Refer To Figure 1-C.
1-56. What type of circuit is shown in figure 1-C? 1. Positive half-wave rectifier 2. Negative half-wave rectifier 3. Full-wave rectifier 4. Clipper 1-57. With the input shown in figure 1-C, which of the following outputs would be correct? 1. 2. 3. 4. 1-58. If the input frequency to a half-wave rectifier is 120 hertz, what is the output frequency of the rectified dc? 1. 30 pps 2. 60 pps 3. 120 pps 4. 240 pps 1-59. Why are the units (plates) of the metallic rectifier stacked? 1. To dissipate heat 2. To be used in more than one circuit 3. To prevent inverse voltage breakdown 4. To handle high current applications 1-60. Which of the following types of rectifiers replaces the bulky selenium rectifier?
1. Copper-oxide rectifier 2. Half-wave rectifier 3. Metallic rectifier 4. Silicon rectifier 1-61. Signal diodes are used for which of the following purposes? 1. As mixers 2. As switches 3. As detectors 4. Each of the above 1-62. What type of bias makes a diode act as an open switch? 1. Direct 2. Reverse 3. Forward 4. Switching 1-63. A standard specification sheet for a diode contains which of the following information? 1. A brief description of the diode 2. Major application of the diode 3. Special features of the diode 4. All of the above 9 ________________________________________
In Answering Questions 1-64 Through
1-66, MATCH THE ELECTRICAL LETTER
Symbol For Rectifier Diodes In
Column B To The Definition In
Column A.
A. Definitions
B. Symbols
1-64. The maximum reverse dc voltage that will not cause breakdown 1. V R 1-65. The peak current specified for a given number of cycles or portion of a cycle 2. I SURGE 1-66. The average reverse current at a specified temperature, usually 60 hertz 3. 4. IF(AV) IR(AV) ________________________________________ 1-67. A matching pair of diodes is indicated by which of the following numbers? 1. 2N325 2. 1N325C 3. 2N325M 4. 1N325M 1-68. The number 3N345 identifies which of the following semiconductors, if any? 1. Diode 2. Transistor 3. Tetrode transistor 4. None of the above 1-69. What type of diode has green, blue, and orange bands?
1. 1N463 2. 1N572 3. 1N663 4. 1N563 1-70. One of the prime dangers to the semiconductor diode is heat. Excessive current generated by heat which eventually destroys a diode is called 1. junction overload 2. thermal runaway 3. thermoplastic action 4. thermionic emission 1-71. When replacing a diode in a circuit, which of the following safety precautions should you observe in removing the diode from the circuit? 1. Do not pry the diode from the circuit 2. Do not use excessive heat to remove the diode 3. Do not remove the diode from the circuit while voltage is applied 4. All of the above 1-72. As you make a front-to-back ratio check of a diode with an ohmmeter, your first measurement (forward) is a low resistance reading, and your second measurement (reverse) is also a low reading. What should be your evaluation of the diode?
1. It is open 2. It is shorted 3. It is good 4. It is leaky 1-73. What are normally the front-to-back ratio of (a) a power rectifier and (b) a signal diode? 1. (a) 10:1 (b) 50:1 2. (a) 10:1 (b) 300:1 3. (a) 300:1 (b) 10:1 4. (a) 300:1 (b) 50:1 10 1-74. Of the following tests, which is the most valid for checking a diode? 1. A forward and reverse resistance check with an ohmmeter 2. The substitution of a new diode for the questionable one 3. A dynamic electrical check with a diode test set 4. A forward and reverse resistance check using two different ohmmeters 11
Assignment 2
Textbook assignment: Chapter 2, “Transistors,” pages 2-1 through 2-53. _________________________________________________________________________________ 2-1. What term is used for a semiconductor that has three or more elements? 1. Diode 2. Transistor 3. Duo-diode 4. Point contact 2-2. The term transistor was derived from which of the following words? 1. Resistance and capacitance 2. Transformer and resistor 3. Resistor and transformer 4. Transfer and resistor 2-3. What are the three elements of a transistor? 1. Anode, base, and collector 2. Cathode, base, and collector 3. Emitter, collector, and base 4. Collector, emitter, and cathode 2-4. In a transistor, the flow of current carriers is controlled by which element(s)?
1. Emitter 2. Collector 3. Both 1 and 2 above 4. Base 2-5. In a transistor schematic, what is indicated by (a) the angular line with the arrowhead and (b) the direction of the arrow? 1. (a) (b) Cathode Direction of current flow 2. (a) (b) Base Direction of current flow 3. (a) (b) Emitter Type of transistor 4. (a) (b) Collector Type of transistor 2-6. Junction transistors have replaced point- contact transistors for which of the following reasons? 1. Junction transistors generate less noise 2. Junction transistors handle more power 3. Junction transistors provide higher current and voltage gains 4. All of the above 2-7. What is the total number of PN junctions in a transistor?
1. One 2. Two 3. Three 4. Four 2-8. What are the two junctions of a transistor? 1. Emitter-base and emitter-collector 2. Emitter-collector and base-collector 3. Emitter-base and collector-emitter 4. Emitter-base and base-collector 2-9. With proper bias applied to a transistor, what should be the relative resistance of (a) the emitter-base junction and (b) the base-collector junction? 1. (a) High (b) low 2. (a) High (b) high 3. (a) Low (b) low 4. (a) Low (b) high 2-10. For normal operation of a transistor, what is the bias of the (a) emitter-base junction and (b) base-collector junction?
1. (a) Forward (b) reverse 2. (a) Forward (b) forward 3. (a) Reverse (b) forward 4. (a) Reverse (b) reverse 12 Figure 2A.—Transistor symbology.
In Answering Questions 2-11
Through 2-15, Refer To Figure 2-A.
Match The Symbol To The Term
Given In The Question.
2-11. The symbol for base current. 1. H 2. D 3. C 4. B 2-12. The symbol for collector current. 1. A 2. C 3. G 4. H 2-13. The symbol for emitter current. 1. B 2. C 3. D 4. F 2-14. The symbol for collector voltage supply. 1. C 2. D 3. E 4. F 2-15. The symbol for base voltage supply. 1. E 2. F 3. G 4. H 2-16. In a transistor, what percent of the total current flows through the emitter lead? 1. 100 2. 98 3. 60 4. 5 2-17. What are the majority current carriers in (a) the PNP transistor and (b) the NPN transistor? 1. (a) Holes (b) holes 2. (a) Holes (b) electrons 3. (a) Elements (b) holes 4. (a) Electrons (b) electrons 2-18. How will the transistor currents be affected if the forward bias provided by VBB is increased?
1. I B will decrease, IE will decrease, and IC will decrease 2. I B will increase, IE will decrease, and IC will decrease 3. I B will increase, IE will decrease, and IC will increase 4. I B will increase, IE will increase, and IC will increase 2-19. What device provides an increase in current, voltage, or power of a signal without appreciably altering the original signal? 1. Diode 2. Amplifier 3. Oscillator 4. Power supply 2-20. The resistor that provides forward bias for the emitter-base junction of a transistor is indicated by which of the following symbols?
1. R T 2. R g 3. R L 4. R B 13 2-21. The collector load resistor is represented by which of the following symbols? 1. R T 2. R g 3. R L 4. R B 2-22. In the quiescent state of a transistor circuit, what does the symbol VC indicate? 1. Collector voltage supply 2. Collector voltage 3. Current gain 4. Capacitor voltage Figure 2B.—A basic transistor amplifier.
In Answering Questions 2-23
Through 2-26, Refer To Figure 2-B.
2-23. What is the purpose of CC? 1. To bypass ac signals to ground 2. To couple the input signal to the amplifier 3. To provide base bias to the preceding stage 4. To prevent ac variations on the base 2-24. When the positive alternation of the input signal is applied at point A, what, if anything, happens to the bias on the base of the transistor? 1. It increases 2. It decreases 3. It remains at its quiescent value 4. Nothing 2-25. When the positive alternation of the input signal is applied at point A, what happens, if anything, to the current through RL?
1. It increases 2. It decreases 3. It remains at its quiescent value 4. Nothing 2-26. When the signal shown at point A is applied to the base of Q1, which of the following signals will be at the output? 1. 3. 2. 4. 2-27. What type of bias keeps the base bias constant and improves thermal stability? 1. Self-bias 2. Fixed bias 3. Combination bias 4. Each of the above 14 Figure 2C.—A transistor amplifier.
In Answering Questions 2-28
Through 2-34, Refer To Figure 2-C.
2-28. Which resistors are fixed biased resistors? 1. R1 and R L 2. R1 and R3 3. R1 and R2 4. R2 and R3 2-29. Which resistor is self-biased? 1. R1 2. R2 3. R3 4. R L 2-30. Which waveform is the output for a class AB amplifier with input number 1? 1. A 2. B 3. C 4. D 2-31. Which waveform is the output for a class A amplifier with input number 2? 1. C 2. D 3. E 4. F 2-32. Which waveform is the output for a class B amplifier with input number 1? 1. A 2. B 3. F 4. G 2-33. Which waveform is the output for a Class C amplifier with input number 2?
1. A 2. B 3. C 4. G 2-34. If the circuit is operating as a class A amplifier, but is being "overdriven," which output waveform is correct? 1. A 2. B 3. C 4. D 2-35. Which class of amplifier allows collector current to flow for a full 360 degrees of the input signal? 1. A 2. B 3. C 4. AB 2-36. Which class of amplifier allows collector current to flow for more than 180 degrees of the input signal but less than 360 degrees? 1. A 2. B 3. C 4. AB 15 2-37. Which class of amplifier has the highest fidelity and lowest efficiency?
1. A 2. B 3. C 4. AB 2-38. Which class of amplifier has the highest efficiency? 1. A 2. B 3. C 4. AB 2-39. What are the three transistor configurations? 1. Common base, common grid, and common output 2. Common anode, common collector, and common base 3. Common emitter, common base, and common collector 4. Common emitter, common base, and common base
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_______________________________________
In Answering Questions 2-40
Through 2-45, Match The
Transistor Configurations Listed
In Column B To The Transistor
CIRCUITS SHOWN IN COLUMN A. (NOTE:
Answers In Column B May Be Used
More Than Once.)
A. Circuits B. Configurations
2-40. 1. 2. 3. Common Emitter Common Base Common Collector 2-41. 2-42. 2-43. 2-44. 2-45. _______________________________________ 16 2-46. Which of the following is a transistor configuration that provides a phase reversal? 1. Common bias 2. Common input 3. Common emitter 4. Common collector 2-47. What is the symbol for input current in a common-emitter configuration? 1. I E 2. I B 3. IC 4. I T 2-48. What is the symbol for input current in a common-base configuration? 1. I E 2. I B 3. IC 4. I T 2-49. What term is used to indicate current gain in a common-emitter configuration?
1. Alpha 2. Beta 3. Gamma 4. X-ray 2-50. What term is used to indicate current gain in a common-collector configuration? 1. Alpha 2. Beta 3. Gamma 4. X-ray 2-51. What term is used to indicate current gain in a common-base configuration? 1. Alpha 2. Beta 3. Gamma 4. X-ray 2-52. Which of the following formulas is used to figure current gain in a common- emitter configuration? 1. 3. 2. 4. 2-53. Which of the following formulas is used to figure current gain in a common-base configuration? 1. 3. 2. 4. 2-54. Which of the following formulas is used to figure current gain in a common- collector configuration?
1. 3. 2. 4. 2-55. The common collector is also referred to by which of the following terms? 1. Low current gain amplifier 2. Voltage amplifier 3. Emitter follower 4. Grounded emitter 17 2-56. Which of the following conditions presents the greatest danger to a transistor? 1. Heat 2. High operating voltage 3. Excessive reverse current 4. Handling of the transistor 2-57. What method for checking transistors is cumbersome when more than one transistor is bad in a circuit? 1. Ohmmeter 2. Transistor checker 3. Voltage check 4. Substitution A. Hybrid IC B. Monolithic IC C. Microelectronics D. Modular Circuitry E. Integrated Circuit F. Printed Circuit Board G. Integrated Circuit Board Figure 2D.—List of microelectronic terminology.
In Answering Questions 2-58
Through 2-62, Select From Figure
2-D THE TERM DEFINED IN THE
Question.
2-58. A broad term used to describe the use of integrated circuits to miniaturize electronic equipment. 1. A 2. B 3. C 4. D 2-59. A flat insulating surface upon which printed wires and miniaturized components are connected in a predetermined design and attached to a common base. 1. A 2. B 3. F 4. G 2-60. An assembly technique in which printed circuit boards are stacked and connected to form a module. 1. B 2. C 3. D 4. E 2-61. A device that integrates both active and passive components of a complete electronic circuit in a single chip.
1. D 2. E 3. F 4. G 2-62. A plastic card on which integrated circuits are mounted. 1. A 2. B 3. F 4. G 18
Assignment 3
Textbook assignment: Chapter 3, “Special Devices,” pages 3-1 through 3-55. _________________________________________________________________________________ 3-1. What is the total number of connections in a diode? 1. One 2. Two 3. Three 4. Four 3-2. When the PN-junction diode is reversed biased, what happens to the majority carriers? 1. They combine with minority carriers at the junction 2. They move toward the junction 3. Both 1 and 2 above 4. They move away from the junction 3-3. What causes a small leakage current in a reverse-biased PN junction?
1. Holes 2. Electrons 3. Minority carriers 4. Majority carriers 3-4. At some potential, as you increase the reverse bias voltage on a PN junction, the reverse current increases very rapidly. What electronic term is given to this voltage potential? 1. Breakdown voltage 2. Reverse-bias 3. Forward-bias 4. Thermal runaway
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3-5. Which of the following is a characteristic of the Zener diode? 1. A PN-junction diode that operates in the reverse-bias breakdown region 2. A PN-junction diode that uses the avalanche effect 3. A PN-junction diode that uses the Zener effect 4. Each of the above 3-6. What determines whether a solid material will act as a conductor, a semiconductor, or an insulator? 1. The energy level of the valence band 2. The energy level of the conductor band 3. The energy difference across the forbidden gap 4. The actual construction of the valence electrons 3-7. In comparing a conductor and an insulator, what is the relative dimension of the forbidden gap of (a) the conductor and (b) the insulator?
1. (a) Wide (b) wide 2. (a) Wide (b) narrow 3. (a) Narrow (b) narrow 4. (a) Narrow (b) wide
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19 3-8. What is the "tunneling phenomenon" within the Zener diode? 1. An action where the minority carriers tunnel across the junction to form the current that occurs at breakdown 2. An action where the majority carriers tunnel across the junction to form the current that occurs at breakdown 3. An action that separates the conduction band and the valence band by a large gap 4. An action that removes all the electrons from the conduction band energy level 3-9. Which breakdown theory explains the action that takes place in a heavily doped PN junction with a reverse bias above 5 volts?
1. Zener effect 2. Avalanche breakdown 3. Energy band effect 4. Valence band gap crossing 3-10. Which breakdown theory explains the action that takes place in a heavily doped PN junction with a reverse bias below 5 volts? 1. Zener effect 2. Avalanche breakdown 3. Energy band effect 4. Valence band gap crossing 3-11. What happens to a Zener diode that has a reverse bias slightly higher than the breakdown voltage? 1. The Zener cuts off 2. The Zener acts like a short circuit 3. The Zener acts like an open circuit 4. The Zener conduction does not change Figure 3A.—Schematic symbols.
In Answering Questions 3-12 And 3-13,
Refer To Figure 3-A.
3-12. Which of the symbols represents a Zener diode? 1. A 2. B 3. C 4. D 3-13. In what direction does current flow in a Zener diode? 1. From point 1 to point 2 2. From point 2 to point 1 3. From point 1 to point 2 to point 3 4. From point 3 to point 2 to point 1 3-14. Why is the Zener diode an ideal voltage regulator? 1. It compensates for low supply voltage 2. It uses an unlimited number of carriers 3. Operating in the breakdown region does not harm it 4. The voltage across the diode remains almost constant after breakdown 20 3-15. In the construction of the tunnel diode, what is the ratio of impurity atoms to semiconductor atoms?
1. 10,000,000: 1000 2. 1,000:10,000,000 3. 10,000: 100,000 4. 100,000: 10,000 Figure 3B. Tunnel diode characteristic curve.
In Answering Questions 3-16
Through 3-18, Refer To Figure 3-B.
3-16. What is/are the most important aspects(s) of the tunnel diode characteristic curve? 1. The forward-current increase to a peak with small applied forward bias 2. The decreasing forward current with an increasing forward bias to a minimum valley current (IV) 3. The normal increasing forward current with further increase in the bias voltage 4. All of the above 3-17. What portion of the characteristic curve is the region of negative resistance? 1. From point 1 to point 2 2. From point 2 to point 3 3. From point 3 to point 4 4. From point 4 to point 5 3-18. At what area on the characteristic curve does the tunnel diode perform like a normal PN junction?
1. From point 0 to point 1 2. From point 1 to point 2 3. From point 2 to point 3 4. From point 3 to point 4 3-19. The varactor operates like which of the following electronic components? 1. A capacitor 2. An inductor 3. A variable capacitor 4. A variable inductor 3-20. An increase in reverse bias of a varactor will have what effect on the width of the depletion region? 1. It will stabilize 2. It will fluctuate 3. It will decrease 4. It will increase 3-21. What happens to the capacitance of a varactor diode as the reverse bias is increased?
1. It decreases 2. It increases 3. It remains the same 3-22. In electronic circuits, how is the varactor used? 1. As a tuning device 2. As a balancing device 3. As an amplifier 4. As a rectifier 3-23. What is/are the basic purpose(s) of the silicon controlled rectifier (SCR)? 1. To function as a switch 2. To function as a regulator 3. To function as a rectifier 4. All of the above 21 3-24. The SCR is equivalent to what electronic device? 1. Diode 2. Tetrode 3. Thyratron 4. Beam power tube 3-25. Which of the following circuits uses an SCR in its electronic circuitry?
1. Computer logic circuit 2. Voltage comparator circuit 3. Antenna power amplifier circuit 4. Each of the above Figure 3C. The schematic symbol for the SCR.
In Answering Question 3-26, Refer To
Figure 3-C.
3-26. What is the impedance between points A and C (a) when the SCR is biased off and (b) when the SCR is at saturation? 1. (a) Low (b) low 2. (a) Low (b) high 3. (a) High (b) high 4. (a) High (b) low Figure 3D. A two-transistor circuit.
In Answering Question 3-27, Refer To
Figure 3-D.
3-27. When a positive current is applied to the gate lead, what happens to the collector current of Q1 and Q2? 1. Increases to a value limited only by the external circuit 2. Increases to a value limited only by the internal circuit 3. Decreases to a value limited only by the external circuit 4. Decreases to a value limited only by the internal circuit 3-28. Once an SCR is turned on by a positive pulse of current applied to the gate lead, what action turns the SCR off? 1. Removing the positive pulse from the gate lead 2. Inserting a negative pulse of current on the gate lead 3. Reducing the collector current to a value below that necessary to maintain conduction 4. Increasing the collector current to a point that the SCR will go into saturation and cut off 3-29. What is the total number of terminals in a TRIAC?
1. One 2. Two 3. Three 4. Four 22 3-30. What is the main difference between the TRIAC and the SCR? 1. The SCR requires a higher input voltage than the TRIAC 2. The TRIAC requires a higher input voltage than the SCR 3. The TRIAC controls and conducts current during both alternations of an ac cycle, while the SCR controls and conducts current during only one alternation 4. The SCR controls and conducts current during both alternations of an ac cycle, while the TRIAC controls and conducts currents during only one alternation 3-31. What name is given to a group of devices that either produce light or use light in their operation?
1. Optoelectronic 2. Ophthalmology 3. Optokenetic 4. Optometry 3-32. In optoelectronic devices, what do the initials LED stand for? 1. Low-emitting diode 2. Low-emitting device 3. Light-emitting diode 4. Light-emitting device 3-33. What determines the color of light emitted by an LED? 1. The type of incandescent bulb used 2. The type of material used 3. The type of bias used 4. The type of fluorescent bulb used 3-34. What is the standard schematic symbol used to designate LEDs? 1. An incandescent bulb with arrows pointing toward the light 2. An incandescent bulb with arrows pointing away from the light 3. A diode with two arrows pointing toward the cathode 4. A diode with two arrows pointing away from the cathode 3-35. The circuit symbols for all optoelectronic devices have arrows pointing either toward them or away from them. When the arrows point toward the symbol, what does this indicate?
1. The device produces light 2. The device uses light 3. The device requires current flow 4. The device produces current flow
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23 Figure 3E. Light-emitting diode.
In Answering Questions 3-36 And 3-37,
Refer To Figure 3-E.
3-36. When a negative voltage is applied to the proper cathodes in an LED display, a number is formed. To produce the numeral 5 on an LED display, which of the following diodes must have a negative potential on their cathodes? 1. ABCDE 2. ABGED 3. AFGCD 4. AFGBC 3-37. If an LED segment has an "8" displayed and the negative bias is removed from diodes F and C, what numeral will be displayed? 1. 1 2. 2 3. 3 4. 4 3-38. When replacing LED displays, which of the following methods should you use to ensure that the replacement display is of the same type as the faulty display?
1. A visual inspection 2. A check of the schematic symbols 3. Both 1 and 2 above 4. A check of the manufacturer's number 3-39. The photodiode acts as what type of electronic device? 1. Variable inductor 2. Variable resistor 3. Nonvariable inductor 4. Nonvariable resistor 3-40. When the photodiode is exposed to an external light, what happens to (a) resistance and (b) current? 1. (a) Increase (b) decreases 2. (a) Increases (b) increases 3. (a) Decreases (b) increases 4. (a) Decreases (b) decreases 3-41. To conduct, how must a photodiode be biased?
1. Reverse biased 2. Forward biased 3. Either 1 or 2 above, depending on light intensity 3-42. Photodiodes are useful in which of the following applications? 1. Computer card readers 2. Photographic light meters 3. Optic scanning equipment 4. Each of the above 3-43. Which of the following optoelectronic devices provides increased, conduction for a given light intensity? 1. LED 2. SCR 3. Phototransistor 4. Phototransformer 3-44. To compensate for ambient light, a phototransistor must have a total number of how many leads?
1. One 2. Two 3. Three 4. Four 24 Figure 3F. Solid-state schematic symbols.
In Answering Questions 3-45
Through 3-47, Select From Figure 3-F
The Schematic Symbol Identified In
The Question.
3-45. Schematic symbol for a photo-diode. 1. A 2. B 3. C 4. D 3-46. Schematic symbol for a two-terminal phototransistor. 1. A 2. B 3. C 4. D 3-47. Schematic symbol for a three-terminal phototransistor. 1. A 2. B 3. C 4. D 3-48. Which of the following devices is similar in operation to a photodiode? 1. Phototransistor 2. Photocell 3. LED 4. SCR 3-49. Which of the following is a typical light to dark resistance ratio of a photocell? 1. 1: 10 2. 1: 100 3. 1: 1000 4. 1:10,000 3-50. Photocells are used in which of the following circuits?
1. Controller 2. Oscillator 3. Amplifier 4. Detector 3-51. How should photovoltaic cells be coupled together to produce a relatively high voltage? 1. Series coupling 2. Parallel coupling 3. Inductive coupling 4. Mechanical coupling 3-52. What is the total number of terminals in a unijunction transistor (UJT)? 1. One 2. Two 3. Three 4. Four 3-53. The UJT has which of the following advantages over the conventional transistor? 1. Fewer terminals 2. Larger bandpass 3. Less bias is required 4. Increased temperature stability 25 3-54. How does the UJT differ from a conventional transistor?
1. The UJT has a second base instead of a collector 2. The UJT has a second emitter instead of a collector 3. The UJT has two collectors 3-55. When properly biased, what area(s) of the UJT act(s) as a resistor? 1. The area between base 1 and base 2 2. The area between emitter 1 and emitter 2 3. The area between collector 1 and collector 2 4. All of the above 3-56. The emitter of the UJT may be compared to what electronic component? 1. A fully charged capacitor 2. The wiper arm of a variable resistor 3. The collector of a conventional transistor 4. The secondary winding of a step-down transformer 3-57. What determines the level of voltage gradient at the emitter-base material contact point of a UJT?
1. The bias voltage 2. The manufacturer's specifications 3. The base area of the emitter 4. The voltage potential between base 2 and emitter 3-58. The UJT conducts from base 1 to (a) what point when it is forward biased and from (b) what point to bass 2 when it is reversed biased? 1. (a) Emitter (b) base 1 2. (a) Emitter (b) emitter 3. (a) Base 2 (b) base 1 4. (a) Base 1 (b) emitter 3-59. UJTs may be used in which of the following circuits? 1. Switching 2. Waveshaping 3. Oscillating 4. Each of the above 3-60. The field-effect transistor (FET) combines what desired characteristic of the vacuum tube with the many other advantages of the transistor?
1. Low output impedance 2. High output impedance 3. Low input impedance 4. High input impedance 3-61. What does the FET use to control the electrostatic field within the transistor? 1. Current 2. Voltage 3. Low input impedance 4. High input impedance 3-62. The junction field-effect transistor's (JFET) gate element corresponds very closely in operation with (a) what part of a conventional transistor and (b) what part of the vacuum tube? 1. (a) Emitter (b) cathode 2. (a) Base (b) grid 3. (a) Base (b) cathode 4. (a) Collector (b) plate 3-63. In the JFET, the portion of the bar between the deposit of gate material is of a smaller cross section than the rest of the bar. What does this cross section form?
1. A gate 2. A drain 3. A source 4. A channel 26 3-64. If a P-type material is used to construct the gate of a JFET, what material should be used to construct the remaining part of the JFET? 1. N-type 2. P-type 3. Mica type 4. Junction type 3-65. What is the key to FET operation? 1. The control of the effective cross- sectional area of the channel 2. The control of the effective cross- sectional area of the gate 3. Both 1 and 2 above 4. The low input impedance compared with the high output impedance 3-66. When reverse bias is applied to the gate lead of a JFET, what happens to (a) source-to-drain resistance of the device and (b) current flow?
1. (a) Decreases (b) decreases 2. (a) Decreases (b) increases 3. (a) Increases (b) decreases 4. (a) Increases (b) increases 3-67. What is the "pinch off" voltage of an FET? 1. The voltage required for the FET to conduct 2. The voltage required to overcome the FET reverse bias 3. The voltage required to reduce drain current to zero 4. The voltage required to reduce gate voltage to zero Figure 3G. JFET common source amplifier.
In Answering Questions 3-68 And 3-69,
Refer To Figure 3-G.
3-68. What type of transistor is shown in figure 3-G? 1. N channel JFET 2. P channel JFET 3. NPN/channel JFET 4. PNP/channel JFET 3-69. The circuit shown has which of the following characteristics? 1. Low impedance, high current gain 2. Low impedance, high voltage gain 3. High impedance, high current gain 4. High impedance, high voltage gain 3-70. The MOSFET has which of the following advantages over the JFET? 1. Less bias 2. Higher input impedance 3. Higher output impedance 4. All of the above 27 3-71. The MOSFET is normally constructed so that it operates in either the depletion mode or the enhancement mode. The depletion mode MOSFET (a) uses what type of bias and (b) has what type of doped channel to cause a depletion of current carriers in the channel?
1. (a) Reverse (b) lightly 2. (a) Forward (b) lightly 3. (a) Reverse (b) heavily 4. (a) Forward (b) heavily 3-72. The enhancement mode MOSFET (a) uses what type of bias and (b) has what type of doped channel to enhance the current carriers in the channel? 1. (a) Reverse (b) lightly 2. (a) Forward (b) lightly 3. (a) Reverse (b) heavily 4. (a) Forward (b) heavily Figure 3H. A MOSFET schematic symbol.
In Answering Question 3-73, Refer To
Figure 3-H.
3-73. Which MOSFET element is identified by the arrow in the schematic symbol shown in figure 3-H? 1. Substrate 2. Source 3. Drain 4. Gate 3-74. What type metal is used in the construction of a MOSFET? 1. Oxide 2. Copper 3. Silver 4. Aluminum 3-75. What is the purpose of the shorting spring in a MOSFET? 1. To shunt the substrate to either the source or gate during operation 2. To protect the device from static electricity during replacement 3. To shunt the gates of a dual-gate MOSFET to make it operate like a single-gate MOSFET 4. To change the gain characteristics of the MOSFET 28
Assignment 4
Textbook assignment: Chapter 4, “Solid-State Power Supplies,” pages 4-1 through 4-62. _________________________________________________________________________________ 4-1. Which of the following is NOT one of the four sections of a basic power supply? 1. Transformer 2. Oscillator 3. Rectifier 4. Filter 4-2. The primary purpose of the transformer in an electronic power supply is to isolate the power supply from ground. 1. True 2. False 4-3. What is the primary function of the rectifier section? 1. To convert dc to ac 2. To convert ac to pulsating dc 3. To increase average voltage output 4. To decrease average voltage output 4-4. What is/are the functions of the filter section?
1. To eliminate dc voltage 2. To increase the amplitude of ac 3. To convert pulsating dc to steady dc 4. All of the above 4-5. The purpose of a center tap in a transformer is to provide 1. two separate dc voltages to the rectifier 2. a step-down voltage to the rectifier 3. pulsating dc to the rectifier 4. two equal voltages from one transformer 4-6. A diode is an ideal rectifier for which, if any, of the following reasons? 1. Current flows through the diode in one direction only 2. Current flows through the diode in both directions 3. Current will not flow through a diode 4. None of the above 4-7. When the anode of a diode is negative with respect to the cathode, the diode is said to be in what state?
1. Conduction 2. Saturation 3. Remission 4. Cutoff 4-8. In a simple half-way rectifier, the diode will conduct for a maximum of how many degrees of the 360-degree input signal? 1. 45 2. 90 3. 180 4. 270 4-9. What term is used to describe current pulses that flow in the same direction? 1. Average current 2. Secondary current 3. Pure direct current 4. Pulsating direct current 4-10. What is the ripple frequency of a half-wave rectifier with an input line frequency of 60 Hz? 1. 30 Hz 2. 60 Hz 3. 90 Hz 4. 120 Hz 29 4-11. In a half-wave rectifier, what is the average voltage output when the peak voltage is 300 volts?
1. 190.8 volts 2. 95.4 volts 3. 19.08 volts 4. 9.4 volts Figure 4A. Complete full-wave rectifier.
In Answering Questions 4-12 And
4-13, REFER TO FIGURE 4-A. ASSUME
That The Voltage Across The
Transformer Secondary (Point A -
Point B) Has An Rms Value Of 480
Volts Ac.
4-12. What is the peak value of the voltage pulse across the load? 1. 169.7 volts 2. 215.8 volts 3. 339.4 volts 4. 480 volts 4-13. What is the average load voltage? 1. 339.4 volts 2. 240 volts 3. 216 volts 4. 189.6 volts 4-14. What is the ripple frequency of a full- wave rectifier with an input line frequency of 60 Hz? 1. 30 Hz 2. 60 Hz 3. 90 Hz 4. 120 Hz 4-15. The full-wave rectifier has which of the following advantages over the half- wave? 1. Higher average voltage and current 2. Larger number of components 3. Higher value of voltage 4. Better regulation 4-16. What is the average voltage output of a full-wave rectifier that has an output of 100 volts peak?
1. 3.18 volts 2. 6.36 volts 3. 31.8 volts 4. 63.7 volts 4-17. The primary disadvantage of the conventional full-wave rectifier is that the peak output voltage is only one-half that of the half-wave rectifier. 1. True 2. False
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30 Figure 4B. Bridge rectifier.
In Answering Questions 4-18 And
4-19, REFER TO FIGURE 4-B. 4-18. When the voltage across the secondary of the transformer has the polarity shown, which of the diodes will conduct? 1. D1 and D3 2. D2 and D4 3. D1 and D2 4. D3 and D4 4-19. When the polarity reverses, which of the diodes will conduct? 1. D3 and D1 2. D4 and D2 3. D2 and D1 4. D4 and D3 4-20. In filter circuits, inductors are used as what type of impedance(s)? 1. Shunt impedance to oppose changes in current 2. Shunt impedances to oppose changes in voltage 3. Series impedances to oppose changes in current 4. Series impedances to oppose changes in voltage 4-21. To retain its charge, the capacitor in a simple capacitor filter must have a long charge time constant and a short discharge time constant.
1. True 2. False 4-22. If you increase the value of a capacitor, the XC will increase. 1. True 2. False 4-23. To obtain a steady dc output in a simple capacitor circuit, the capacitor must charge almost instantaneously to the value of the applied voltage. 1. True 2. False 4-24. Which of the following factors, if any, determines the rate of discharge of the capacitor in a filter circuit? 1. The value of the load resistance 2. The amount of voltage 3. The type of capacitor 4. None of the above 4-25. A half-wave rectifier has an output frequency of 60 hertz, a filter capacitor value of 40 microfarads, and a load resistance of 10 kilohms. What is the value of XC?
1. 133.3 ohms 2. 26.5 ohms 3. 66.3 ohms 4. 40.0 ohms 31 4-26. A full-wave rectifier has an output frequency of 120 hertz, a filter capacitor value of 25 microfarads, and a load resistance of 10 kilohms.What is the value of XC? 1. 5.3 ohms 2. 53 ohms 3. 106 ohms 4. 1060 ohms 4-27. What type of filter is the most basic power supply filter? 1. Capacitor 2. LC choke-input 3. LC capacitor-input 4. RC capacitor-input 4-28. In a circuit with a capacitor filter, how is the capacitor connected? 1. In series with the load 2. In parallel with the load 3. In series with the input 4. Both 2 and 3 above 4-29. The LC choke-input filter is used primarily where which of the following types of regulation is/are important?
1. Frequency 2. Current only 3. Voltage only 4. Voltage and Current 4-30. In an LC choke-input filter circuit, the capacitor charges only to the average value of the input voltage. What component inhibits the capacitor from reaching the peak value of the input voltage? 1. The diode 2. The capacitor 3. The filter choke 4. The load resistor 4-31. In an LC choke-input filter, the larger the value of the filter capacitor, the better the filtering action. Which of the following factors represents the major limitation in obtaining the maximum value of the capacitor used?
1. Cost 2. Reliability 3. Availability 4. Physical size 4-32. What is the most common range of values, in henries, for a power supply choke? 1. 1 to 20 2. 5 to 25 3. 25 to 30 4. 10 to 200 4-33. If the impedance of the choke in an LC choke-input filter is increased, the ripple will 1. increase 2. decrease 3. oscillate 4. remain the same 4-34. A full-wave rectifier has an output frequency of 120 hertz, a filter choke with a value of 10 henries, and a load resistance of 10 kilohms. What is the value of XL? 1. 75 ohms 2. 7.5 ohms 3. 75 kilohms 4. 7.5 kilohms 4-35. The filter capacitor in the LC choke- input filter is NOT subject to extreme voltage surges because of the protection provided by what component?
1. Shunt capacitor 2. Series resistor 3. Load resistor 4. Inductor 32 4-36. Shorted turns in the choke of an LC choke-input filter may reduce the value of inductance below the critical value. When this happens, which of the following problems may occur? 1. Poor voltage regulation 2. Excessive ripple amplitude 3. Abnormally high output voltage 4. Each of the above 4-37. The use of the RC capacitor-input filter is limited to which of the following situations? 1. When the load current is large 2. When the load current is small 3. When the load voltage is large 4. When the load voltage is small Figure 4C. RC capacitor-input filter.
In Answering Questions 4-38 And
4-39, REFER TO FIGURE 4-C. 4-38. Which of the components will have the highest failure rate? 1. C1 2. C2 3. R1 4. R L 4-39. Which of the components provides protection against voltage surges in the circuit? 1. C1 2. C2 3. R1 4. R L Figure 4D. LC Capacitor-input filter.
In Answering Questions 4-40 And
4-41, REFER TO FIGURE 4-D. 4-40. Components L1 and C2 form what type of circuit? 1. Ac voltage doubler 2. Dc voltage doubler 3. Ac voltage divider 4. Dc voltage divider 4-41. If component L1 shorts to the core, which of the following conditions will result? 1. Low output ripple frequency 2. Excessive ripple frequency 3. Excessively high output 4. No output 4-42. In a voltage regulator, what percent of regulation would be ideal? 1. 1 % 2. 5 % 3. 3 % 4. 0 % 33
In Answering Questions 4-43
Through 4-45, Refer To The
FOLLOWING FORMULA: 4-43. If a power supply produces 30 volts with no load and 25 volts under full load, what is the percent of regulation? 1. 5 2. 10 3. 20 4. 30 4-44. If a power supply produces 10 volts with no load and 9 volts under full load, what is the percent of regulation? 1. 8 2. 9 3. 10 4. 11 4-45. If a power supply produces 20 volts with no load and 20 volts under full load, what is the percent of regulation? 1. 1 2. 2 3. 3 4. 0 4-46. Basic voltage regulators are classified as either series or shunt. Their classification is determined by which of the following factors?
1. The type of regulating device used 2. The type of regulation required 3. The amount of regulation required 4. The position of the regulating device in relation to the load (RL) 4-47. The simple series voltage regulator was designed to function as what type of resistance? 1. Fixed resistance in series with the load 2. Fixed resistance in parallel with the load 3. Variable resistance in series with the load 4. Variable resistance in parallel with the load 4-48. A series voltage regulator is designed so that what total percentage of current flows through the regulating device?
1. 25 2. 50 3. 75 4. 100 4-49. When a series voltage regulator is used to control output voltages, any increase in input voltage results in a/an 1. decrease in the voltage drop across the load resistance 2. increase in the voltage drop across the Zener diode 3. decrease in the resistance of the regulating device 4. increase in the resistance of the regulating device
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Intentionally.
34 Figure 4E. Simple shunt voltage regulator.
In Answering Questions 4-50
Through 4-52, Refer To Figure 4-E.
4-50. The base-emitter bias across Q1 is determined by which of the components? 1. R1 and CR1 2. R1 and R S 3. R S and CR1 4. R S and RL 4-51. What, if anything, happens to the forward bias of Q1 when the input voltage increases? 1. It increases 2. It decreases 3. Nothing, it remains the same 4-52. When the load current increases and the output voltage momentarily drops, what, if anything, happens to the resistance of Q1? 1. It increases to compensate for the drop 2. It decreases to compensate for the change 3. Nothing, it remains the same 4-53. What type of ammeter reading indicates that current regulator is functioning properly?
1. Constant 2. Deflection in the negative direction 3. Deflection in the positive direction 4. Fluctuation around the center line 4-54. A major disadvantage of having good current regulation is that good voltage regulation is lost. 1. True 2. False 4-55. To maintain a constant current flow when there is an increase in the load resistance (RL), variable resistance (RV) must compensate for this change by 1. increasing its resistance 2. decreasing its resistance 3. remaining the same 4-56. A decrease in the forward bias of a base- emitter junction has which of the following effects on the resistance of a transistor?
1. It increases 2. It deceases 3. It remains the same 4-57. Voltage multipliers are used primarily to develop what type of voltage? 1. Low voltage where low current is required 2. Low voltage where high current is required 3. High voltage where low current is required 4. High voltage where high current is required 4-58. The classification of voltage multipliers depends on which of the following ratios? 1. Input current to output current 2. Input current to output voltage 3. Output voltage to input voltage 4. Input voltage to output current 35 4-59. A half-wave voltage doubler consists of what total number of half-wave rectifiers?
1. One 2. Two 3. Three 4. Four 4-60. If a half-wave rectifier circuit is added to a half-wave voltage doubler circuit, what will be the resulting circuit? 1. A voltage doubler 2. A voltage tripler 3. A voltage quadruplet 4. A voltage quintuplet 4-61. Which of the following methods is used by manufacturers of electronic equipment to reduce the cost of extensive wiring? 1. Grounding the output of the power supply to the chassis 2. Grounding the return side of the power transformer to the chassis 3. Connecting all components in parallel 4. Connecting all components in series 4-62. When working on electronic equipment, the technician should observe which of the following safety precautions?
1. Make certain that the electronic equipment is properly grounded 2. Make certain that the test equipment is properly grounded 3. Make certain that the rubber mats are in good condition 4. All of the above 4-63. Which of the following is/are the most widely used check(s) for testing electronic equipment? 1. Smoke 2. Visual 3. Signal tracing 4. Both 2 and 3 above 4-64. Any connection that is located close to the chassis or to any other terminal should be examined for the possibility of which of the following problems?
1. An open 2. A short 3. A low resistance 4. A high resistance 4-65. Which of the following statements applies to a transformer that is discolored or leaking? 1. It is operational 2. It is cracked 3. It is shorted 4. It is open 4-66. As a technician, you notice that a resistor is discolored and charred. Which, if any, of the following conditions most likely caused the damage? 1. Overload 2. Open circuit 3. Ambient temperature 4. None of the above 4-67. You are in the process of energizing a power supply. You hear a boiling or sputtering noise and notice smoke coming from a section of the power supply. Which, if any, of the following actions should you take first?
1. Secure the power immediately 2. Examine the problem area 3. Remove the defective component 4. None of the above 4-68. Which, if any, of the following is the most rapid and accurate method for testing electronic circuits after completing visual inspection? 1. Smoke test 2. Current test 3. Signal tracing 4. None of the above