NEETS_v07_SolidState_Q___A

8/3/2019 NEETS_v07_SolidState_Q___A

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1. Semiconductor Diodes.............................................................................................. 1-1Q1. What is a solid-state device?A1. An electronic device that operates by virtue of the movement of electrons within asolid piece of semiconductor material.

Q2. Define the term negative temperature coefficient.

A2. It is the decrease in a semiconductors resistance as temperature rises

Q3. Name three of the largest users of semiconductor devices.A3. Space systems, computers, and data processing equipment.

Q4. State one requirement of an electron tube, which does not exist for semiconductors,that makes the tube less efficient than the semiconductor.A4. The electron tube requires filament or heater voltage, whereas the semiconductordevice does not;consequently, no power input is spent by the semiconductor forconduction.

Q5. Define matter and list its three different states.

A5. Anything that occupies space and has weight. Solid, liquid, and gas.

Q6. What is the smallest particle into which an element can be broken down and stillretain all itsoriginal properties?A6. The atom.

Q7. What are the three particles that comprise an atom and state the type of charge theyhold?A7. Electrons-negative, protons-positive, and neutrons-neutral.

Q8. What is the outer shell of an atom called?

A8. The valence shell.

Q9. What term is used to describe the definite discrete amounts of energy required tomove an electron from a low shell to a higher shell?A9. Quanta.

Q10. What is a negative ion?A10. A negatively charged atom having more than its normal amount of electrons.

Q11. What is the main difference in the energy arrangement between an isolated atomand the atom in a solid?A11. The energy levels of an atom in a solid group together to form energy bands,

whereas the isolated atom does not.

Q12. What determines, in terms of energy bands, whether a substance is a goodinsulator,semiconductor, or conductor?A12. The width of the forbidden band.

Q13. What determines the chemical activity of an atom?A13. The number of electrons in the valence shell.


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Q14. What is the term used to describe the sharing of valence electrons between two ormore atoms?A14. Covalent bonding.

Q15. Name the two types of current flow in a semiconductor.

A15. Electron flow and hole flow.

Q16. What is the name given to a piece of pure semiconductor material that has anequal number of electrons and holes?A16. Intrinsic.

Q17. What is the name given to a doped germanium crystal with an excess of freeholes?A17. P-type crystal.

Q18. What are the majority carriers in an N-type semiconductor?A18. Electrons.

Q19. What is the purpose of a PN junction diode?A19. To convert alternating current into direct current.

Q20. In reference to the schematic symbol for a diode, do electrons flow toward or awayfrom thearrow?A20. Toward the arrow.

Q21. What type of PN diode is formed by using a fine metal wire and a section of N-typesemiconductor material?A21. Point-contact.

Q22. What are the majority carriers in a P-type semiconductor?A22. Holes.

Q23. Conduction in which type of semiconductor material is similar to conduction in acopper wire?A23. N-type material.

Q24. What is the name of the area in a PN junction that has a shortage of electrons andholes?A24. Depletion region.

Q25. In order to reverse bias in a PN junction, what terminal of a battery is connected tothe Pmaterial?A25. Negative.

Q26. What type of bias opposes the PN junction barrier?A26. Forward.

Q27. What is a load?


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A27. Any device that draws current.

Q28. What is the output of a half-wave rectifier?A28. A pulsating dc voltage.

Q29. What type of rectifier is constructed by sandwiching a section of semiconductor

material between two metal plates?A29. Metallic rectifier.

Q30. What type of bias makes a diode act as a closed switch?A30. Forward bias.

Q31. What is used to show how diode parameters vary over a full operating range?A31. A characteristic curve.

Q32. What is meant by diode ratings?A32. They are the limiting values of operating conditions outside which operations couldcause diode damage.

Q33. What does the letter "N" indicate in the semiconductor identification system?A33. A semiconductor.

Q34. What type of diode has orange, blue, and gray bands?A34. 1N368.

Q35. What is the greatest threat to a diode?A35. Heat.

Q36. When checking a diode with an ohmmeter, what is indicated by two high resistancemeasurements?

A36. The diode is open or has a high-forward resistance.

2. Transistors ................................................................................................................ 2-1

Q1. What is the name given to the semiconductor device that has three or moreelements?A1. Transistor

Q2. What electronic function made the transistor famous?A2. Amplification.

Q3. In which direction does the arrow point on an NPN transistor?A3. Outward.

Q4. What was the name of the very first transistor?A4. Point-contact.

Q5. What is one of the most important parts of any transistor manufacturing process?A5. Quality control.


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Q6. To properly bias an NPN transistor, what polarity voltage is applied to the collector,and what is its relationship to the base voltage?A6. Positive, more positive.

Q7. Why is conduction through the forward-biased junction of an NPN transistorprimarily in one direction, namely from the emitter to base?

A7. Because the N material on one side of the forward-biased junction is more heavilydoped than theP-material.

Q8. In the NPN transistor, what section is made very thin compared with the other twosections?A8. The P or base section.

Q9. What percentage of current in an NPN transistor reaches the collector?A9. 98 percent.

Q10. What are the majority current carriers in a PNP transistor?

A10. Holes.

Q11. What is the relationship between the polarity of the voltage applied to the PNPtransistor and that applied to the NPN transistor?A11. The polarity of voltage applied to the PNP transistor is opposite of that applied tothe NPN transistor

Q12. What is the letter designation for base current?A12. I B.

Q13. Name the two current loops in a transistor.A13. The base current loop and the collector current loop.

Q14. What is the name of the device that provides an increase in current, voltage, orpower of a signal without appreciably altering the original signal?A14. Amplifier.

Q15. Besides eliminating the emitter-base battery, what other advantages can differentbiasing methods offer?A15. Compensation for slight variations in transistor characteristics and changes intransistor conduction because of temperature variations.

Q16. In the basic transistor amplifier discussed earlier, what is the relationship betweenthe polarity of the input and output signals?

A16. The signals are opposite in polarity or 180 degrees out of phase with each other.

Q17. What is the primary difference between the NPN and PNP amplifiers?A17. The polarity of the source voltage.

Q18. Which biasing method is the most unstable?A18. Base current bias or fixed bias.


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Q19. What type of bias is used where only moderate changes in ambient temperatureare expected?A19. Self-bias.

Q20. When is degeneration tolerable in an amplifier?A20. When it is necessary to prevent amplitude distortion.

Q21. What is the most widely used combination-bias system?A21. The voltage-divider type.

Q22. What amplifier class of operation allows collector current to flow during thecomplete cycle of the input?A22. Class A.

Q23. What is the name of the term used to describe the condition in a transistor whenthe emitter-base junction has zero bias or is reverse biased and there is no collectorcurrent?A23. Cutoff.

Q24. What two primary items determine the class of operation of an amplifier?A24. The amount of bias and the amplitude of the input signal.

Q25. What amplifier class of operation is the most inefficient but has the least distortion?A25. Class A.

Q26. What are the three transistor configurations?A26. Common emitter (CE), common base (CB), and common collector (CC).

Q27. Which transistor configuration provides a phase reversal between the input andoutput signals?

A27. Common emitter.

Q28. What is the input current in the common-emitter circuit?A28. Base current (I B).

Q29. What is the current gain in a common-base circuit called?

A29. Alpha

Q30. Which transistor configuration has a current gain of less than 1?A30. Common base.

Q31. What is the output current in the common-collector circuit?A31. IE.

Q32. Which transistor configuration has the highest input resistance?A32. Common collector.

Q33. What is the formula for GAMMA ?


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Q34. List three items of information normally included in the general description sectionof a specification sheet for a transistor.A34. The kind of transistor, the transistor's common applications, and mechanical data.

Q35. What does the number "2" (before the letter "N") indicate in the JAN markingscheme?A35. The number of junctions in the device, which in this case indicates a transistor.

Q36. What is the greatest danger to a transistor?A36. Heat.

Q37. What method for checking transistors is cumbersome when more than one

transistor is bad in a circuit?A37. The substitution method.

Q38. What safety precaution must be taken before replacing a transistor?A38. The power must be removed from the circuit.

Q39. How is the collector lead identified on an oval-shaped transistor?A39. By the wide space between the collector lead and the other two leads (emitter andbase).

Q40. What are two transistor tests that can be done with an ohmmeter?A40. Gain and junction resistance.

Q41. When you are testing the gain of an audio-frequency transistor with an ohmmeter,what is indicated by a 10-to-1 resistance ratio?A41. Normal gain.

Q42. When you are using an ohmmeter to test a transistor for leakage, what is indicatedby a low, but not shorted, reverse resistance reading?A42. A leaking transistor

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3. Special Devices ........................................................................................................ 3-1

Q1. In a reverse biased PN-junction, which current carriers cause leakage current?A1. The minority carriers.

Q2. The action of a PN-junction during breakdown can be explained by what twotheories?A2. Zener effect and avalanche effect.

Q3. Which breakdown theory explains the action that takes place in a heavily doped PN-junction with a reverse bias of less than 5 volts?


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Q18. When used for ac current control, during which alternation of the ac cycle does theTRIAC control current flow?A18. During both alternations.

Q19. What type of bias is required to cause an LED to produce light?A19. Forward bias.

Q20. When compared to incandescent lamps, what is the power requirement of an LED?A20. Very low.

Q21. In a common anode, seven-segment LED display, an individual LED will light if anegative voltage is applied to what element?A21. The cathode.

Q22. What is the resistance level of a photodiode in total darkness?A22. Very high.

Q23. What type of bias is required for proper operation of a photodiode?A23. Reverse bias.

Q24. What is a typical light-to-dark resistance ratio for a photocell?A24. 1:1000.

Q25. What semiconductor device produces electrical energy when exposed to light?A25. Photovoltaic cell.

Q26. The UJT has how many PN junctions?A26. One.

Q27. The area between base 1 and base 2 in a UJT acts as what type of common circuitcomponent?A27. Variable resistor.

Q28. The sequential rise in voltage between the two bases of the UJT is called what?A28. A voltage gradient.

Q29. What is the normal current path for a UJT?A29. From base 1 to the emitter.

Q30. What is one of the primary advantages of the FET when compared to the bipolar

transistor?A30. High input impedance.

Q31. The FET and the vacuum tube have what in common?A31. Voltage controls conduction.

Q32. The base of a transistor serves a purpose similar to what element of the FET?A32. Gate.


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Q33. What are the two types of JFET?A33. N-channel and P-channel.

Q34. The source and drain of an N-channel JFET are made of what type of material?A34. N-type material.

Q35. What is the key to FET operation?A35. Effective cross-sectional area of the channel.

Q36. What is the normal current path in an N-channel JFET?A36. From source to drain.

Q37. Applying a reverse bias to the gate of an FET has what effect?A37. Source-to-drain resistance increases.

Q38. The input and output signals of a JFET amplifier have what phase relationship?A38. They are 180 degrees out of phase.

Q39. When compared to the JFET, what is the input impedance of the MOSFET?A39. The MOSFET has a higher input impedance.

Q40. What are the four elements of the MOSFET?A40. Gate, source, drain, and substrate.

Q41. The substrate of an N-channel MOSFET is made of what material?A41. P-type material.

Q42. In a MOSFET, which element is insulated from the channel material?A42. The gate terminal.

Q43. What type of MOSFET can be independently controlled by two separate signals?A43. The dual-gate MOSFET.

Q44. What is the purpose of the spring or wire around the leads of a new MOSFET?A44. To prevent damage from static electricity.

4. Solid-State Power Supplies ...................................................................................... 4-1

Q1. What are the four basic sections of a power supply?A1. Transformer, rectifier, filter, regulator.

Q2. What is the purpose of the rectifier section?

A2. To change ac to pulsating dc.

Q3. What is the purpose of the filter section?A3. To change pulsating dc to pure dc.

Q4. What is the purpose of the regulator section?A4. To maintain a constant voltage to the load.

Q5. What is the name of the simplest type of rectifier which uses one diode?


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A5. The half-wave rectifier.

Q6. If the output of a half-wave rectifier is 50-volts peak, what is the average voltage?A6. 15.9 volts.

Q7. In addition to stepping up or stepping down the input line voltage, what additional

purpose does the transformer serve?A7. It isolates the chassis from the power line.

Q8. What was the major factor that led to the development of the full-wave rectifier?A8. The fact that the full-wave rectifier uses the full output, both half cycles, of thetransformer.

Q9. What is the ripple frequency of a full-wave rectifier with an input frequency of 60 Hz?A9. 120 hertz.

Q10. What is the average voltage (Eavg) Output of a full-wave rectifier with an output of100 volts peak?A10. 63.7 volts.

Q11. What is the main disadvantage of a conventional full-wave rectifier?A11. Peak voltage is half that of the half-wave rectifier.

Q12. What main advantage does a bridge rectifier have over a conventional full-waverectifier?A12. The bridge rectifier can produce twice the voltage with the same size transformer.

Q13. If you increase the value of the capacitor, will the XC increase or decrease? Why?

A13. It will decrease. Capacitance is inversely proportional to:

Q14. What is the most basic type of filter?A14. The capacitor filter.

Q15. In a capacitor filter, is the capacitor in series or in parallel with the load?A15. Parallel.

Q16. Is filtering better at a high frequency or at a low frequency?A16. At a high frequency.

Q17. Does a filter circuit increase or decrease the average output voltage?A17. A filter circuit increases the average output voltage.

Q18. What determines the rate of discharge of the capacitor in a filter circuit?A18. Value of capacitance and load resistance.

Q19. Does low ripple voltage indicate good or bad filtering?A19. Good.

Q20. Is a full-wave rectifier output easier to filter than that of a half-wave rectifier?


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A20. Yes.

Q21. In an LC choke-input filter, what prevents the rapid charging of the capacitor?A21. The CEMF of the inductor.

Q22. What is the range of values usually chosen for a choke?

A22. From 1 to 20 henries.

Q23. If the impedance of the choke is increased, will the ripple amplitude increase ordecrease?A23. Decrease.

Q24. Why is the use of large value capacitors in filter circuits discouraged?A24. Expense.

Q25. When is a second RC filter stage used?A25. When ripple must be held at an absolute minimum.

Q26. What is the most commonly used filter today?A26. LC capacitor-input filter.

Q27. What are the two main disadvantages of an LC capacitor filter?A27. Cost and size of the inductor.

Q28. Circuits which maintain constant voltage or current outputs are called dc voltage ordc currentA28. Regulators.

Q29. The purpose of a voltage regulator is to provide an output voltage with little or no___.

A29. Variation.

Q30. The two basic types of voltage regulators are ___ and ___.A30. Series and shunt.

Q31. When a series voltage regulator is used to control output voltages, any increase inthe input voltage results in an increase/a decrease (which one) in the resistance of theregulating device.A31. An increase.

Q32. A shunt-type voltage regulator is connected in serial/parallel (which one) with theload resistance.

A32. In parallel.

Q38. A half-wave voltage doubler is made up of how many half-wave rectifiers?A38. Two.

Q39. If a half-wave rectifier is added to a half-wave voltage doubler, the resulting circuitis a voltage____.A39. Trippler.


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Q40. In a full-wave voltage doubler, are the capacitors connected in series or in parallelwith the output load?A40. In parallel.

Q41. What is the most important thing to remember when troubleshooting?A41. Safety precautions.

Q42. What is the main reason for grounding the return side of the transformer to thechassis?A42. To eliminate shock hazard.

Q43. What are two types of checks used in troubleshooting power supplies?A43. Visual and signal tracing.

NEETS_v07_SolidState_Q___A

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