Assignmentname

1. Describe the construction and operation of a capacitor.

2. Name the three types of capacitors.

3. Describe the three uses of capacitors.

4. Name and explain both current flow theories.

5. Describe how a semicondor differs from a conductor or an insulator.

6. What are two common types of semiconductor material.

7. Explain what "Doping " is and how N-Type or P-Type material is made.

8. Describe the function and construction of a "Diode".

9. Explain the term PN junction.

10. Describe the depletion region of a diode.

11. What is the voltage drop (the voltmeter reading) of a diode?

12. Explain the terms "Forward" and "Reverse" Bias.

13. Describe Rectification and how diodes are used.

14. Explain the difference between half-wave and full-wave rectification.

15. Describe the function of a De-spiking (Voltage Suppression) diode.

16. Explain the operation of a De-spiking (Voltage Suppression) diode.

17. Describe the function of an Isolation diode.

18. Explain the operation of an Isolation diode.

19. Explain how a "Zener Diode" differs from a conventional diode.

20. Explain the term "Zener Point" (Avalanche Point) and what happens at this point.

21. Explain how a "Light Emitting Diode" (LED) differs from a conventional diode.

22. What is the voltage drop (the voltmeter reading) of an LED?

THE BIPOLAR TRANSISTOR

TRANSISTORS

A transistor can be used as an amplifier to control electric motor speed such as AC blower motors, or as solid state switches to control actuators such as fuel injectors.

This chapter will cover each of the following four areas:

Transistor Operation Transistor Applications Transistor Gain Integrated Circuits

Transistors are made from the same N-type and P-type materials as diodes and employ the same principles. Transistors, however, have two PN junctions instead of just one like a diode has. The two PN junctions allow a transistor to perform more functions than a diode, such as acting as a switch or an amplifier.

The bipolar transistor is made up of three parts: the emitter, the base and the collector. There are two types of bipolar transistors: the PNP and the NPN. In the PNP transistor the emitter is made from P-type material, the base is N-type material and the collector is P-type material. For the PN transistor to operate, the emitter must be connected to positive, the base to negative and the collector to negative.

The NPN transistor has an emitter made from N-type material. Its base is P-type material and the collector is N-type material. For the NPN transistor to operate, the emitter must be connected to negative, the base to positive and the collector to positive Aside from the way in which the NPN and PNP transistors are connected in the circa they operate the same way. Both transistor have a forward biased junction and a reverse biased junction, and three parts-the emitter, the base and the collector-formed in a three-layer arrangement tr ic tr ic

Current flow between the emitter and base controls the current flow between the emitter and collector. The emitter of the transistor is the most heavily doped so it has the most excess electrons or holes, depending on whether the emitter is P-type or N-type material. The collector is doped slightly less than the emitter and the base is very thin with the fewest doping atoms. As a result of this type of doping, the current flow in the emitter-collector is much greater than in the emitter-base. By regulating the current at the emitter-base junction, the amount of current allowed to pass from the emitter to the collector can be controlled.

in the emitter points away from the center so the current flow is from the base to emitter and from the collector to emitter.

One of the most common uses of a transistor in an automobile is as a switch. Switching transistors can be found in solid state control modules and computers. They control devices on the car such as the fuel injector in an EFI car or a mechanical relay that operates the retract motor on a car with retractable headlights. When an NPN transistor is used as a switch, the emitter of the transistor is grounded and the base is connected to positive. If the voltage is removed from the base, no current flows from the emitter to the collector and the transistor is off. When the base is forward biased by a large enough voltage, current will flow from the emitter to the collector. Essentially, the transistor is being used to control a large current with a small current like a starter relay. A small amount of current to the relay will complete a circuit so a large current can flow.

The symbols for both PNP and NPN transistors are very similar. The distinguishing feature is the arrow, which is always located in the emitter and always points in the direction of conventional current flow. The base is part of the symbol which looks like a "T" and the remaining line, opposite the emitter, is the collector. In the symbol for a PNP transistor the arrow in the emitter points toward the center so the current flow is from emitter to base and from emitter to collector. In the NPN transistor the arrow

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