Neets Module 7 Assignment 3

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CVN68
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Neets Module 7 Assignment 3
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2012-08-09 16:29:41
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  1. In a reverse biased PN-junction, which current carriers cause leakage current?
    The minority carriers.
  2. The action of a PN-junction during breakdown can be explained by what two theories?
    Zener effect and avalanche effect.
  3. Which breakdown theory explains the action that takes place in a heavily doped PN-junction with a reverse bias of less than 5 volts?
    Zener effect.
  4. What is the doping level of an avalanche effect diode when compared to the doping level of a Zener-effect diode?
    The doping level of an avalanche effect diode is lower.
  5. During avalanche effect breakdown, what limits current flow through the diode?
    An external current-limiting resistor.
  6. Why is electron flow with the arrow in the symbol of a Zener diode instead of against the arrow as it is in a normal diode?
    Because Zener diodes are operated in the reverse bias mode.
  7. What is the main difference in construction between normal PN junction diodes and tunnel diodes?
    The amount of doping.
  8. What resistance property is found in tunnel diodes but not in normal diodes?
    Negative resistance.
  9. When compared to the ordinary diode, the tunnel diode has what type of depletion region?
    The tunnel diode has a very narrow depletion region.
  10. In the tunnel diode, the tunneling current is at what level when the forbidden gap of the N-type material is at the same energy level as the empty states of the P-type material?
    Minimum.
  11. The varactor displays what useful electrical property?
    Variable capacitance.
  12. When a PN junction is forward biased, what happens to the depletion region?
    The depletion region decreases.
  13. When the reverse bias on a varactor is increased, what happens to the effective capacitance?
    Capacitance decreases.
  14. The SCR is primarily used for what function?
    The SCR is primarily used for switching power on or off.
  15. When an SCR is forward biased, what is needed to cause it to conduct?
    A gate signal.
  16. What is the only way to cause an SCR to stop conducting?
    The forward bias must be reduced below the minimum conduction level.
  17. The TRIAC is similar in operation to what device?
    SCR.
  18. When used for ac current control, during which alternation of the ac cycle does the TRIAC control current flow?
    During both alternations.
  19. What type of bias is required to cause an LED to produce light?
    Forward bias.
  20. When compared to incandescent lamps, what is the power requirement of an LED?
    Very low.
  21. In a common anode, seven-segment LED display, an individual LED will light if a negative voltage is applied to what element?
    The cathode.
  22. What is the resistance level of a photodiode in total darkness?
    Very high.
  23. What type of bias is required for proper operation of a photodiode?
    Reverse bias.
  24. What is a typical light-to-dark resistance ratio for a photocell?
    1:1000.
  25. What semiconductor device produces electrical energy when exposed to light?
    Photovoltaic cell.
  26. The UJT has how many PN junctions?
    One.
  27. The area between base 1 and base 2 in a UJT acts as what type of common circuit component?
    Variable resistor.
  28. The sequential rise in voltage between the two bases of the UJT is called what?
    A voltage gradient.
  29. What is the normal current path for a UJT?
    From base 1 to the emitter.
  30. What is one of the primary advantages of the FET when compared to the bipolar transistor?
    High input impedance.
  31. The FET and the vacuum tube have what in common?
    Voltage controls conduction.
  32. The base of a transistor serves a purpose similar to what element of the FET?
    Gate.
  33. What are the two types of JFET?
    N-channel and P-channel.
  34. The source and drain of an N-channel JFET are made of what type of material?
    N-type material.
  35. What is the key to FET operation?
    Effective cross-sectional area of the channel.
  36. What is the normal current path in an N-channel JFET?
    From source to drain.
  37. Applying a reverse bias to the gate of an FET has what effect?
    Source-to-drain resistance increases.
  38. The input and output signals of a JFET amplifier have what phase relationship?
    They are 180 degrees out of phase.
  39. When compared to the JFET, what is the input impedance of the MOSFET?
    The MOSFET has a higher input impedance.
  40. What are the four elements of the MOSFET?
    Gate, source, drain, and substrate.
  41. The substrate of an N-channel MOSFET is made of what material?
    P-type material.
  42. In a MOSFET, which element is insulated from the channel material?
    The gate terminal.
  43. What type of MOSFET can be independently controlled by two separate signals?
    The dual-gate MOSFET.
  44. What is the purpose of the spring or wire around the leads of a new MOSFET?
    To prevent damage from static electricity.

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