Turning the Transistor On

Chapter Turning the Transistor On

Complete Electronics Self Teaching Guide with Projects
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Complete Electronics Self Teaching Guide with Projects

  • CHAPTER 4 THE TRANSISTOR SWITCH136When you complete this chapter, you will be able to do the following: ■ Calculate the base resistance, which turns a transistor ON and OFF. ■ Explain how one transistor turns another ON and OFF. ■ Calculate various currents and resistances in simple transistor switching circuits. ■ Calculate various resistances and currents in switching circuits, which contain two transistors. ■ Compare the switching action of a junction field effect transistor (JFET) to a BJT.TURNING THE TRANSISTOR ON1  Start by examining how to turn a transistor ON by using the simple circuit shown in Figure 4.1. In Chapter 3, RB was given, and you had to find the value of collector current and voltages. Now, do the reverse. Start with the current through RC, and find the value of RB that turns the transistor ON and permits the collector current to flow.RBRCVCVSFIGURE 4.1QUESTIONWhat current values do you need to know to find RB?ANSWERThe base and collector currentsBook Authorc04V107/04/2012 2:59 PM c04.indd 1367/4/2012 3:00:31 PM