UNIVERSITY OF NAIROBI COLLEGE OF BIOLOGICAL AND PHYSICAL SCIENCES FACULTY OF SCIENCE SPH 307 INTRODUCTORY ELECTRONICS Dr. Kenneth A. Kaduki Department of Physics University of Nairobi Reviewer: Prof. Bernard O. Aduda
SPH 307 INTRODUCTORY ELECTRONICS INTRODUCTION All of us have used electronic equipment of one type or the other. Most of our homes have radios and, increasingly, television and electronic apparatus of other kinds are being considered as standard domestic equipment. Mobile phones, personal computers, and CD players provide further proof that electronics is vital to a developing economy like ours. This series of ten lectures is intended as an introduction to the exciting field of electronics for students with no prior knowledge of the technical aspects of the subject. The primary goal of the lectures is to present the basic principles of operation of electronic devices and demonstrate their utilization in circuit applications. You will also be introduced to the analytical tools and techniques required to solve a variety of practical problems in electronics. Learning Objectives: Upon completion of this study unit you should be able to: Apply Kirchoff s laws to electronic circuits and derive the basic equations Apply the following fundamental techniques for the analysis of resistive circuits: superposition theorem; Thevenin s theorem; Norton s theorem. Describe the basic principles underlying the physics of semiconductor devices in general and the PN junction in particular. Explain the operation of selected diode-based circuits. Describe the operation of transistors. Determine and select the operation point of transistors. Draw transistor amplifier circuits and explain how they work. Describe the process of Integrated Circuit (IC) manufacture. Compute the gain of Simple Operational Amplifier based amplification circuits. List the major classes of sensors and explain the principle of operation of selected sensors. Describe the principle of operation of various optoelectronic devices. ii
The material is in the following order: I start by presenting Kirchoff s laws and network theorems. These two lectures will provide the tools you require for the systematic analysis of a wide range of direct current (dc) circuits. In lecture 3, I present semiconductor theory, the diode (pn junction) and diode characteristics. Lecture 4 introduces a few basic diode based circuits. In lectures 5 to 7, I discuss the construction and characteristics of transistors and show how they can be assembled into basic voltage amplifiers. Integrated circuits (ICs) have led to a systems approach to electronics. In lecture 8, I present a brief section on the manufacture of ICs. This is followed by a discussion of the characteristics and basic applications of the Operational Amplifier (Op Amp) the most commonly used linear IC. The last two lectures provide an introduction to transducers and optoelectronic devices respectively. I have included a number of questions and exercises after each lecture summary. You should attempt these questions before advancing to the next lecture. Self test questions are also provided at various points of each lecture. You should attempt these questions before moving on to the material that follows. Answers to the self test questions are provided at the end of each lecture. The text books listed below are useful references for most of the material presented in this study unit: 1. A. P. Malvino, Electronic Principles, Tata McGraw-Hill Publishing Company Limited, New Delhi (1999) 2. R. Grob, Basic Electronics, Tata McGraw-Hill Publishing Company Limited, New Delhi (1997) Please feel free to point out any errors that you come across as you read these lecture notes. Dr. Kenneth Amiga Kaduki Senior Lecturer, Department of Physics, Faculty of Science, University of Nairobi April 2005 iii
CONTENT PAGE INTRODUCTION ii LECTURE 1: KIRCHOFFS LAWS 1.1 Introduction 1 1.2 Basic Circuit Elements 1 1.3 Kirchoff s Current Law (KCL) 2 1.4 Kirchoff s Voltage Law (KVL) 5 1.5 Method of Branch Currents 7 1.6 Node Voltage Analysis 11 1.7 Method of Mesh Currents 15 1.8 Summary 19 1.9 Exercises 20 LECTURE 2: NETWORK THEOREMS 2.1 Introduction 22 2.2 Superposition 22 2.3 Thevenin s Theorem 25 2.4 Thevenizing a Circuit with Two Voltage Sources 29 2.5 Thevenizing a Bridge Circuit 31 2.6 Norton s Theorem 33 2.8 Summary 38 2.9 Exercises 38 LECTURE 3: SEMICONDUCTORS 3.1 Introduction 40 3.2 Semiconductors 40 3.3 Electrons and Holes 42 3.4 Extrinsic Conductivity 43 3.5 Majority and Minority Carriers 44 3.6 Compensation 45 3.7 The pn Junction 45 3.8 Biased pn Junction 46 3.9 Avalanche Breakdown 48 3.10 Summary 52 3.11 Exercises 53 LECTURE 4: DIODE CIRCUITS 4.1 Introduction 54 4.2 The Half Wave Rectifier 54 4.3 The Full Wave Rectifier 55 4.4 Waveform Filtering (Smoothing) 58 4.5 Voltage Doubler Circuit 62 4.6 Clippers and Clampers 63 4.7 Summary 65 4.8 Exercises 65 iv
5. BIPOLAR JUNCTION TRANSISTOR (BJT) 5.1 Introduction 67 5.2 Construction and Symbols of the BJT 67 5.3 Transistor Action 69 5.4 Transistor Currents 71 5.5 The Common Emitter (CE) Characteristics 73 5.6 Summary 78 5.7 Exercises 79 6. VOLTAGE AMPLIFICATION 6.1 Introduction 80 6.2 Load Resistor 80 6.3 Working Point and Bias 81 6.4 Coupling Capacitors 82 6.5 Stabilizing the Operating Point 84 6.6 Fully Stabilized Voltage Amplifier 86 6.7 Constant Emitter Current Bias 87 6.8 DC Load Line and Collector Bias 89 6.9 Measurement of the Voltage Gain 93 6.10 Summary 93 6.11 Exercises 93 7. FIELD EFFECT TRANSISTOR (FET) 7.1 Introduction 95 7.2 Construction and Symbols of the JFET 96 7.3 Terminal Characteristics of the JFET 98 7.4 Bias Line and Load Line for JFET Amplifier 101 7.5 Establishing Bounds on Q-Point Location 104 7.6 Graphical Analysis of JFET Amplifiers 105 7.7 Transconductance 106 7.8 Construction and Symbols of the MOSFET 107 7.9 Terminal Characteristics of the MOSFET 108 7.10 Summary 110 7.11 Exercises 110 8. INTEGRATED CIRCUITS 8.1 Introduction 112 8.2 Manufacture of Integrated Circuits 112 8.3 Ideal and Practical Operational Amplifiers (Op Amps) 117 8.4 Op Amp based Amplification Circuits 119 8.5 Wein Bridge Oscillator 125 8.6 Summary 127 8.7 Exercises 128 9. TRANSDUCERS 9.1 Introduction 130 9.2 Classification of Transducers 130 9.3 Thermistor 133 9.4 Thermocouple 135 9.5 Resistance Temperature Detector (RTD) 136 9.6 The Linear Variable Differential Transformer (LVDT) 138 v
9.7 Strain Gauge 139 9.8 Summary 141 9.9 Exercises 142 10. OPTOELECTRONIC DEVICES 10.1 Introduction 144 10.2 Light Sources 145 10.3 Light Detectors 150 10.4 Optocouplers 152 10.5 Summary 153 10.6 Exercises 153 vi