;

# 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.

Copyright � 2007 - 2012 Hawk's Perch Technical Writing, LLC - All rights reserved