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# Lecture Notes - Chapter 3

(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).

## Introduction to The Transistor

• Understanding Transistors
•  Discuss the similarity of a bipolar transistor to two diodes placed back-to-back (figure 3.2).
• Discuss the structure of a bipolar transistor(figure 3.3).
• Introduce the terms; Emitter, Collector, and Base (figure 3.4).
• Introduce the schematic symbol for NPN transistors (figure 3.5).
• Introduce the schematic symbol for PNP transistors (figure 3.6)
• Introduce the term base current (IB).
• Review the equation to calculate IB.
• Introduce the term; transistor action.
• Introduce the term; collector current.
• Discuss the direction in which base current and collector current flow (figure 3.13).
• Introduce the term; current gain (β).
• Review the equation for current gain.
• Inside The Bipolar Transistor
• Discuss the depletion regions present in an unbiased transistor.
• Forward bias on the base-emitter junction shrinks the depletion region.
• The base region is thin, allowing electrons from the emitter to pass through to the collector and current to flow.
• Calculating Currents
• Introduce the equation β = IC/IB.
• Discuss the use of this equation to determine IB.
• Discuss the use of this equation to determine IC .
• Discuss Project 3.1: The Transistor
• Review the circuit (figure 3.19).
• Mention that this experiment is a demonstration of the relationship between beta and the base and collector currents.
• Turning a Transistor ON
• Discuss the similarity of a ON transistor to a closed switch (figure 3.24)
• Introduce the term; Saturated Transistor
• Discuss Project 3.2: The Saturated Transistor
• This project uses the same circuit used in Project 3.1.
• Discuss the relationship, shown in this project, between IB, IC and VC as the transistor becomes saturated.
• Turning a Transistor OFF
• Discuss the similarity of a OFF transistor to a open switch (figure 3.26).
• The Junction Field Effect Transistor (JFET)
• Introduce the terms; source, drain and gate.
• Discuss the structure and schematic symbols of JFETs (figure 3.28).
• Review a typical biasing circuit for a JFET (figure 3.29).
• Introduce the terms; normally ON, and normally OFF.
• Inside the JFET
• Discuss how the depletion regions cut off current flow in the channel when negative voltage is applied to the gate of a N-channel JFET.
• Introduce the term; cutoff voltage.

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