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Lecture Notes - Chapter 4

(These Lecture Notes are for courses using the book the Complete Electronics Self-Teaching Guide with Projects. Instructors of courses using that text are permitted to use these Lecture Notes as-is or adapt them for their use).

The Transistor Switch

  • Turning the Transistor ON
    • Discuss the use of a lamp in place of the collector resistor RC (figure 4.3).
    • Introduce the terms; load and load current.
    • Review the equation to calculate the required load current.
    • Discuss the calculation to determine the base current that will result in the required load current.
    • Show the calculation used to determine the value of the base resistor needed to obtain the desired base current.
  • Why Transistors are used as Switches
    • Discuss the advantages of transistor switches vs. mechanical switches.
  • Discuss Project 4.1: The Transistor Switch
    • Review the circuit diagram (figure 4.9).
    • Mention that circuits similar to this are commonly used in stores to ring a buzzer when a customer walks through the door.
  • The Two Transistors Switch
    • Discuss the two transistor switch circuit (figure 4.16)
    • Summarize how the voltages and currents in the circuit change when the switch is changed from position A to position B (figure 4.17).
    • Discuss the calculations needed to find the values of R1, R2 and R3 to produce  a specified load current.
  • The Three Transistor Switch
    • Discuss the three transistor switch circuit (figure 4.19)
    • Summarize how the voltages and currents in the circuit change when the switch is changed from position A to position B.
    • Discuss the calculations needed to find the values of R1, R2, R3 and R4 to produce a specified load current.
  • Alternative Base Switching
    • Discuss the transistor circuit with the base terminal at the junction of R1 and R2 (figure 4.20).
    • Discuss the calculations needed to find the values of R1 and R2.
  • Discuss Project 4.2: The JFET
    • Review the circuit diagram (figure 4.22).
    • Discuss the expected result of this project; the I-V curve for the JFET.
  • Switching the JFET
    • Review the JFET circuit diagram (figure 4.29).
    • Discuss the calculations needed to find the value of RD.

 

This page includes material extracted, by permission of the publisher, Wiley Publishing, from Complete Electronics Self-Teaching Guide with Projects, ISBN: 9781118217320.

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