Complete Electronics Self-Teaching Guide with Projects Read online

  Table of Contents

  Chapter 1: DC Review and Pre-Test

  Current Flow

  Ohm's Law

  Resistors in Series

  Resistors in Parallel

  Power

  Small Currents

  The Graph of Resistance

  The Voltage Divider

  The Current Divider

  Switches

  Capacitors in a DC Circuit

  Summary

  DC Pre-Test

  Chapter 2: The Diode

  Understanding Diodes

  Diode Breakdown

  The Zener Diode

  Summary

  Self-Test

  Chapter 3: Introduction to the Transistor

  Understanding Transistors

  The Junction Field Effect Transistor (JFET)

  Summary

  Self-Test

  Chapter 4: The Transistor Switch

  Turning the Transistor On

  Turning Off the Transistor

  Why Transistors Are Used as Switches

  The Three-Transistor Switch

  Alternative Base Switching

  Switching the JFET

  Summary

  Self-Test

  Chapter 5: AC Pre-Test and Review

  The Generator

  Resistors in AC Circuits

  Capacitors in AC Circuits

  The Inductor in an AC Circuit

  Resonance

  Summary

  Self-Test

  Chapter 6: Filters

  Capacitors in AC Circuits

  Capacitors and Resistors in Series

  Phase Shift of an RC Circuit

  Resistor and Capacitor in Parallel

  Inductors in AC Circuits

  Phase Shift for an RL Circuit

  Summary

  Self-Test

  Chapter 7: Resonant Circuits

  The Capacitor and Inductor in Series

  The Output Curve

  Introduction to Oscillators

  Summary

  Self-Test

  Chapter 8: Transistor Amplifiers

  Working with Transistor Amplifiers

  A Stable Amplifier

  Biasing

  The Emitter Follower

  Analyzing an Amplifier

  The JFET as an Amplifier

  The Operational Amplifier

  Summary

  Self-Test

  Chapter 9: Oscillators

  Understanding Oscillators

  Feedback

  The Colpitts Oscillator

  The Hartley Oscillator

  The Armstrong Oscillator

  Practical Oscillator Design

  Simple Oscillator Design Procedure

  Oscillator Troubleshooting Checklist

  Summary and Applications

  Self-Test

  Chapter 10: The Transformer

  Transformer Basics

  Transformers in Communications Circuits

  Summary and Applications

  Self-Test

  Answers to Self-Test

  Chapter 11: Power Supply Circuits

  Diodes in AC Circuits Produce Pulsating DC

  Level DC (Smoothing Pulsating DC)

  Summary

  Self-Test

  Chapter 12: Conclusion and Final Self-Test

  Conclusion

  Final Self-Test

  Appendix A: Glossary

  Appendix B: List of Symbols and Abbreviations

  Appendix C: Powers of Ten and Engineering Prefixes

  Appendix D: Standard Composition Resistor Values

  Appendix E: Supplemental Resources

  Web Sites

  Books

  Magazines

  Suppliers

  Appendix F: Equation Reference

  Appendix G: Schematic Symbols Used in This Book

  Introduction

  What This Book Teaches

  How This Book Is Organized

  Conventions Used in This Book

  How to Use This Book

  Chapter 1

  DC Review and Pre-Test

  Electronics cannot be studied without first understanding the basics of electricity. This chapter is a review and pre-test on those aspects of direct current (DC) that apply to electronics. By no means does it cover the whole DC theory, but merely those topics that are essential to simple electronics.

  This chapter reviews the following:

  Current flow

  Potential or voltage difference

  Ohm's law

  Resistors in series and parallel

  Power

  Small currents

  Resistance graphs

  Kirchhoff's Voltage Law

  Kirchhoff's Current Law

  Voltage and current dividers

  Switches

  Capacitor charging and discharging

  Capacitors in series and parallel

  Current Flow

  1 Electrical and electronic devices work because of an electric current.

  Question

  What is an electric current?

  Answer

  An electric current is a flow of electric charge. The electric charge usually consists of negatively charged electrons. However, in semiconductors, there are also positive charge carriers called holes.

  2 There are several methods that can be used to generate an electric current.

  Question

  Write at least three ways an electron flow (or current) can be generated.

  Answer

  The following is a list of the most common ways to generate current:

  Magnetically—This includes the induction of electrons in a wire rotating within a magnetic field. An example of this would be generators turned by water, wind, or steam, or the fan belt in a car.

  Chemically—This involves the electrochemical generation of electrons by reactions between chemicals and electrodes (as in batteries).

  Photovoltaic generation of electrons—This occurs when light strikes semiconductor crystals (as in solar cells).

  Less common methods to generate an electric current include the following:

  Thermal generation—This uses temperature differences between thermocouple junctions. Thermal generation is used in generators on spacecrafts that are fueled by radioactive material.

  Electrochemical reaction—This occurs between hydrogen, oxygen, and electrodes (fuel cells).

  Piezoelectrical—This involves mechanical deformation of piezoelectric substances. For example, piezoelectric material in the heels of shoes power LEDs that light up when you walk.

  3 Most of the simple examples in this book contain a battery as the voltage source. As such, the source provides a potential difference to a circuit that enables a current to flow. An electric current is a flow of electric charge. In the case of a battery, electrons are the electric charge, and they flow from the terminal that has an excess number of electrons to the terminal that has a deficiency of electrons. This flow takes place in any complete circuit that is connected to battery terminals. It is this difference in the charge that creates the potential difference in the battery. The electrons try to balance the difference.

  Because electrons have a negative charge, they actually flow from the negative terminal and return to the positive terminal. This direction of flow is called electron flow. Most books, however, use current flow, which is in the opposite direction. It is referred to as conventional current flow, or simply current flow. In this book, the term conventional current flow is used in all circuits.

  Later in this book, you see that many semiconductor devices have a symbol t
hat contains an arrowhead pointing in the direction of conventional current flow.

  Questions

  A. Draw arrows to show the current flow in Figure 1.1. The symbol for the battery shows its polarity.

  Figure 1.1

  B. What indicates that a potential difference is present? __________

  C. What does the potential difference cause? __________

  D. What will happen if the battery is reversed? __________

  Answers

  A. See Figure 1.2.

  Figure 1.2

  B. The battery symbol indicates that a difference of potential (also called voltage) is being supplied to the circuit.

  C. Voltage causes current to flow if there is a complete circuit present, as shown in Figure 1.1.

  D. The current flows in the opposite direction.

  Ohm's Law

  4 Ohm's law states the fundamental relationship between voltage, current, and resistance.

  Question

  What is the algebraic formula for Ohm's law? _____

  Answer

  This is the most basic equation in electricity, and you should know it well. Some electronics books state Ohm's law as E = IR. E and V are both symbols for voltage. This book uses V to indicate voltage. When V is used after a number in equations and circuit diagrams, it represents volts, the unit of measurement of voltage. Also, in this formula, resistance is the opposition to current flow. Larger resistance results in smaller current for any given voltage.

  5 Use Ohm's law to find the answers in this problem.

  Questions

  What is the voltage for each combination of resistance and current values?

  A. R = 20 ohms, I = 0.5 amperes

  V = _____

  B. R = 560 ohms, I = 0.02 amperes

  V = _____

  C. R = 1,000 ohms, I = 0.01 amperes

  V = _____

  D. R = 20 ohms I = 1.5 amperes

  V = _____

  Answers

  A. 10 volts

  B. 11.2 volts

  C. 10 volts

  D. 30 volts

  6 You can rearrange Ohm's law to calculate current values.

  Questions

  What is the current for each combination of voltage and resistance values?

  A. V = 1 volt, R = 2 ohms

  I = _____

  B. V = 2 volts, R = 10 ohms

  I = _____

  C. V = 10 volts, R = 3 ohms

  I = _____

  D. V = 120 volts, R = 100 ohms

  I = _____

  Answers

  A. 0.5 amperes

  B. 0.2 amperes

  C. 3.3 amperes

  D. 1.2 amperes

  7 You can rearrange Ohm's law to calculate resistance values.

  Questions

  What is the resistance for each combination of voltage and current values?

  A. V = 1 volt, I = 1 ampere

  R = _____

  B. V = 2 volts, I = 0.5 ampere

  R = _____

  C. V = 10 volts, I = 3 amperes

  R = _____

  D. V = 50 volts, I = 20 amperes

  R = _____

  Answers

  A. 1 ohm

  B. 4 ohms

  C. 3.3 ohms

  D. 2.5 ohms

  8 Work through these examples. In each case, two factors are given and you must find the third.

  Questions

  What are the missing values?

  A. 12 volts and 10 ohms. Find the current. __________

  B. 24 volts and 8 amperes. Find the resistance. __________

  C. 5 amperes and 75 ohms. Find the voltage. _____

  Answers

  A. 1.2 amperes

  B. 3 ohms

  C. 375 volts

  Inside the Resistor

  Resistors are used to control the current that flows through a portion of a circuit. You can use Ohm's law to select the value of a resistor that gives you the correct current in a circuit. For a given voltage, the current flowing through a circuit increases when using smaller resistor values and decreases when using larger resistor values.

  This resistor value works something like pipes that run water through a plumbing system. For example, to deliver the large water flow required by your water heater, you might use a 1-inch diameter pipe. To connect a bathroom sink to the water supply requires much smaller water flow and, therefore, works with a 1/2-inch pipe. In the same way, smaller resistor values (meaning less resistance) increase current flow, whereas larger resistor values (meaning more resistance) decrease the flow.

  Tolerance refers to how precise a stated resistor value is. When you buy fixed resistors (in contrast to variable resistors that are used in some of the projects in this book), they have a particular resistance value. Their tolerance tells you how close to that value their resistance will be. For example, a 1,000-ohm resistor with ± 5 percent tolerance could have a value of anywhere from 950 ohms to 1,050 ohms. A 1,000-ohm resistor with ± 1 percent tolerance (referred to as a precision resistor) could have a value ranging anywhere from 990 ohms to 1,010 ohms. Although you are assured that the resistance of a precision resistor will be close to its stated value, the resistor with ± 1 percent tolerance costs more to manufacture and, therefore, costs you more than twice as much as a resistor with ± 5 percent.

  Most electronic circuits are designed to work with resistors with ± 5 percent tolerance. The most commonly used type of resistor with ± 5 percent tolerance is called a carbon film resistor. This term refers to the manufacturing process in which a carbon film is deposited on an insulator. The thickness and width of the carbon film determines the resistance (the thicker the carbon film, the lower the resistance). Carbon film resistors work well in all the projects in this book.

  On the other hand, precision resistors contain a metal film deposited on an insulator. The thickness and width of the metal film determines the resistance. These resistors are called metal film resistors and are used in circuits for precision devices such as test instruments.

  Resistors are marked with four or five color bands to show the value and tolerance of the resistor, as illustrated in the following figure. The four-band color code is used for most resistors. As shown in the figure, by adding a fifth band, you get a five-band color code. Five-band color codes are used to provide more precise values in precision resistors.

  The following table shows the value of each color used in the bands:

  By studying this table, you can see how this code works. For example, if a resistor is marked with orange, blue, brown, and gold bands, its nominal resistance value is 360 ohms with a tolerance of ± 5 percent. If a resistor is marked with red, orange, violet, black, and brown, its nominal resistance value is 237 ohms with a tolerance of ± 1 percent.

  Resistors in Series

  9 You can connect resistors in series. Figure 1.3 shows two resistors in series.

  Figure 1.3

  Question

  What is their total resistance? _____

  Answers

  The total resistance is often called the equivalent series resistance and is denoted as Req.

  Resistors in Parallel

  10 You can connect resistors in parallel, as shown in Figure 1.4.

  Figure 1.4

  Question

  What is the total resistance here? _____

  Answers

  RT is often called the equivalent parallel resistance.

  11 The simple formula from problem 10 can be extended to include as many resistors as wanted.

  Question

  What is the formula for three resistors in parallel? _____

  Answers

  You often see this formula in the following form:

  12 In the following exercises, two resistors are connected in parallel.

  Questions

  What is the total or equivalent resistance?

  A. R1 = 1 ohm, R2 = 1 ohm

  RT = _____

  B. R1 = 1,000 ohms, R2 = 500 ohms

  RT = _____


  C. R1 = 3,600 ohms, R2 = 1,800 ohms

  RT = _____

  Answers

  A. 0.5 ohms

  B. 333 ohms

  C. 1,200 ohms

  RT is always smaller than the smallest of the resistors in parallel.

  Power

  13 When current flows through a resistor, it dissipates power, usually in the form of heat. Power is expressed in terms of watts.

  Question

  What is the formula for power? _____

  Answers

  There are three formulas for calculating power:

  14 The first formula shown in problem 13 allows power to be calculated when only the voltage and current are known.

  Questions

  What is the power dissipated by a resistor for the following voltage and current values?

  A. V = 10 volts, I = 3 amperes

  P = _____

  B. V = 100 volts, I = 5 amperes

  P = _____

  C. V = 120 volts, I = 10 amperes

  P = _____

  Answers

  A. 30 watts.

  B. 500 watts, or 0.5 kW. (The abbreviation kW indicates kilowatts.)

  C. 1,200 watts, or 1.2 kW.

  15 The second formula shown in problem 13 allows power to be calculated when only the current and resistance are known.

  Questions

  What is the power dissipated by a resistor given the following resistance and current values?

  A. R = 20 ohm, I = 0.5 ampere

  P = _____

  B. R = 560 ohms, I = 0.02 ampere

  P = _____

  C. V = 1 volt, R = 2 ohms

  P = _____

  D. V = 2 volt, R = 10 ohms

  P = _____

  Answers

  A. 5 watts

  B. 0.224 watts

  C. 0.5 watts

  D. 0.4 watts