Basic of Electronics PDF

i BASIC OF ELECTRONICS Authored By Dr. Brijesh Iyer Assistant Professor (Sel. Gr.) Department of E & TC Engineering Dr. Babasaheb Ambedkar Technological University, Lonere Lonere, Maharashtra...

i BASIC OF ELECTRONICS Authored By Dr. Brijesh Iyer Assistant Professor (Sel. Gr.) Department of E & TC Engineering Dr. Babasaheb Ambedkar Technological University, Lonere Lonere, Maharashtra (India) Reviewed By Dr. Sanjay Nalbalwar Professor & Head Department of E & TC Engineering Dr. Babasaheb Ambedkar Technological University, Lonere Lonere, Maharashtra (India) All India Council for Technical Education Nelson Mandela Marg, Vasant Kunj, New Delhi, 110070 ii  BOOK AUTHOR DETAILS Dr. Brijesh Iyer, Assistant Professor (Sel. Gr.), Department of E & TC Engineering, Dr. Babasaheb Ambedkar Technological University, Lonere, Maharashtra (India) Email ID: [email protected] BOOK REVIEWER DETAILS Dr. Sanjay Nalbalwar, Professor & Head, Department of E & TC Engineering, Dr. Babasaheb Ambedkar Technological University, Lonere, Maharashtra (India) Email ID: [email protected] BOOK COORDINATOR (S) – English Version 1. Dr. Ramesh Unnikrishnan, Advisor-II, Training and Learning Bureau, All India Council for Technical Education (AICTE), New Delhi, India Email ID: [email protected] Phone Number: 011-29581215 2. Dr. Sunil Luthra, Director, Training and Learning Bureau, All India Council for Technical Education (AICTE), New Delhi, India Email ID: [email protected] Phone Number: 011-29581210 3. Mr. Sanjoy Das, Assistant Director, Training and Learning Bureau, All India Council for Technical Education (AICTE), New Delhi, India Email ID: [email protected] Phone Number: 011-29581339 July, 2023 © All India Council for Technical Education (AICTE) ISBN : 978-81-963773-2-8 All rights reserved. No part of this work may be reproduced in any form, by mimeograph or any other means, without permission in writing from the All India Council for Technical Education (AICTE). Further information about All India Council for Technical Education (AICTE) courses may be obtained from the Council Office at Nelson Mandela Marg, Vasant Kunj, New Delhi-110070. Printed and published by All India Council for Technical Education (AICTE), New Delhi. Attribution-Non Commercial-Share Alike 4.0 International (CC BY-NC-SA 4.0) Disclaimer: The website links provided by the author in this book are placed for informational, educational & reference purpose only. The Publisher do not endorse these website links or the views of the speaker / content of the said weblinks. In case of any dispute, all legal matters to be settled under Delhi Jurisdiction, only. iii iv  ACKNOWLEDGEMENT The author is grateful to the authorities of AICTE, particularly Prof. T.G. Sitharam, Chairman; Dr. Abhay Jere, Vice-Chairman; Prof. Rajiv Kumar, Member-Secretary, Dr. Ramesh Unnikrishnan, Advisor-II and Dr. Sunil Luthra, Director, Training and Learning Bureau for their planning to publish the books on Basic of Electronics. I would like to express my sincere appreciation to Dr. Sanjay Nalbalwar, Professor & Head of the Department of E&TC Engineering at Dr. Babasaheb Ambedkar Technological University, Lonere-402103(MS)-India, for his contributions as a book reviewer. His efforts have made the book more accessible to students and have given it an artistic touch, resulting in a better overall shape. I am deeply grateful to my wife, Dr. Prachi, and my children, Ku. Rajnandini and Chi. Prabhasdatt, for their unwavering patience throughout the completion of this project. Without their support, this work would not have come to fruition. I would also like to acknowledge the reference books that have been instrumental in the preparation of this book: "Electronic Devices and Circuit Theory" by Robert Boylestad and Louis Nashelsky, "Digital Fundamentals" by Thomas Floyd, "Electronic Instrumentation and Measurements" by David Bell, and "A Course In Electrical and Electronic Measurements and Instrumentation" by A.K. Sawhney. Additionally, I extend my gratitude to Mr. Dixit Jain of Synergy Books Pvt. Ltd. Mumbai for his initial support and motivation. Over the years, my students have made significant contributions that have enriched my experience and expertise in this subject. I am immensely grateful for their valuable input. This book is the result of various suggestions provided by members of the All India Council for Technical Education (AICTE), experts, and authors who have shared their opinions and thoughts on advancing engineering education in our country. I extend my heartfelt acknowledgment to these contributors and all the individuals working in this field whose published books, review articles, papers, photographs, footnotes, references, and other valuable information have enriched our work during the writing process. Dr. Brijesh Iyer v  PREFACE I take great pleasure in introducing the textbook "Basic of Electronics," which is the culmination of my extensive experience in teaching fundamental courses in electronics engineering. The motivation behind writing this book is to provide engineering students with a comprehensive understanding of the basic concepts and fundamentals of electronics engineering, allowing them to gain insight into the subject. With a focus on broad coverage and essential supplementary information, the book incorporates topics recommended by the All India Council for Technical Education (AICTE) in a systematic and organized manner. Special effort has been made to explain the fundamental concepts in the simplest possible way. Throughout the preparation process, I extensively referred to various standard textbooks and developed sections such as critical questions, solved and supplementary problems, and more. Emphasis has been placed on definitions, laws, and comprehensive synopses of formulas for quick revision of the basic principles. The book addresses a wide range of medium and advanced- level problems, presented in a logical and systematic manner. These problem gradations have been tested over many years of teaching, catering to diverse student backgrounds. In addition to relevant illustrations and examples, the book is enriched with solved problems in each unit to facilitate a comprehensive understanding of the topics. Each chapter is accompanied by solved examples, exercise questions, self-study questions, and multiple-choice questions. I sincerely hope that this book will inspire students to delve into and discuss the underlying ideas behind the basic principles of electronics engineering. It aims to establish a solid foundation in the subject matter. I welcome and appreciate all valuable comments and suggestions that will contribute to the enhancement of future editions of this book. It is my utmost pleasure to present this book to both teachers and students. Working on the various aspects covered in this book has been a truly gratifying experience. Dr. Brijesh Iyer vi  OUTCOME BASED EDUCATION For the implementation of an outcome-based education, the first requirement is to develop an outcome- based curriculum and incorporate an outcome-based assessment in the education system. By going through outcome-based assessments evaluators will be able to evaluate whether the students have achieved the outlined standard, specific and measurable outcomes. With the proper incorporation of outcome-based education, there will be a definite commitment to achieve a minimum standard for all learners without giving up at any level. At the end of the program running with the aid of outcome-based education, a student will be able to arrive at the following outcomes: PO1. Engineering knowledge: Apply the knowledge of mathematics, science, engineering fundamentals, and an engineering specialization to the solution of complex engineering problems. PO2. Problem analysis: Identity, formulate, review research literature, and analyze complex engineering problems reaching substantiated conclusions using the first principles of mathematics, natural sciences, and engineering sciences. PO3. Design/development of solutions: Design solutions for complex engineering problems and design system components or processes that meet the specified needs with appropriate consideration for public health and safety, and cultural, societal, and environmental considerations. PO4. Conduct investigations of complex problems: Use research-based knowledge and research methods including design of experiments, analysis and interpretation of data, and synthesis of the information to provide valid conclusions. PO5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern engineering and IT tools including prediction and modeling to complex engineering activities with an understanding of the limitations. PO6. The engineer and society: Apply reasoning informed by the contextual knowledge to assess societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to the professional engineering practice. PO7. Environment and sustainability: Understand the impact of professional engineering solutions in societal and environmental contexts, and demonstrate the knowledge of, and need for sustainable development. PO8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities and norms of the engineering practice. PO9. Individual and team work: Function effectively as an individual, and as a member or leader in diverse teams, and in multidisciplinary settings. PO10. Communication: Communicate effectively on complex engineering activities with the engineering community and with society at large, such as being able to comprehend and write effective reports and design documentation, make effective presentations, and give and receive clear instructions. PO11. Project management and finance: Demonstrate knowledge and understanding of the engineering and management principles and apply these to one’s own work, as a member and leader in a team, to manage projects and in multidisciplinary environments. PO12. Life-long learning: Recognize the need for, and have the preparation and ability to engage in independent and life-long learning in the broadest context of technological change. vii  COURSE OUTCOMES After completion of the course, the students will be able to: CO-1: Apply basic ideas and principles of Electronics Engineering CO-2: To study of PN Junction devices and its applications CO-3: To study the construction, working of a transistor and apply its characteristics CO-4: To understand the concept of feedback amplifiers and oscillators CO-5: To know the the fundamentals of Op-Amp its applications CO-6: To understand the working principles of various measuring instruments and transducers CO-7: To acquire the fundamental concepts of digital electronics. Expected Mapping with Programme Outcomes Course (1‐ Weak Correlation; 2‐ Medium correlation; 3‐ Strong Correlation) Outcomes PO‐1 PO‐2 PO‐3 PO‐4 PO‐5 PO‐6 PO‐7 PO‐8 PO‐9 PO‐10 PO‐11 PO‐12 CO‐1 3 3 2 1 - 1 - - - - - 1 CO‐2 3 3 2 1 - - - - - - - - CO‐3 3 3 2 1 - - - - - - - - CO‐4 3 3 3 2 - - - - - - - - CO‐5 3 3 3 1 - - - - - - - - CO‐6 3 3 2 2 - - - - - - - - CO‐7 3 3 3 1 - 1 - - - - - - viii  GUIDELINES FOR TEACHERS To implement Outcome Based Education (OBE) knowledge level and skill set of the students should be enhanced. Teachers should take major responsibility for the proper implementation of OBE. Some of the responsibilities (not limited to) for the teachers in the OBE system may be as follows:  Within reasonable constraints, they should manoeuvre the time to the best advantage of all students.  They should assess the students only upon certain defined criteria without considering any other potential ineligibility to discriminate against them.  They should try to grow the learning abilities of the students to a certain level before they leave the institute.  They should try to ensure that all the students are equipped with quality knowledge as well as competence after they finish their education.  They should always encourage the students to develop their ultimate performance capabilities.  They should facilitate and encourage group work and teamwork to consolidate newer approaches.  They should follow Blooms taxonomy in every part of the assessment. Bloom’s Taxonomy Teacher should Students should be Possible Mode of Level Check able to Assessment Student's ability to Create Design or Create Mini project create Student's ability to Evaluate Argue or Defend Assignment justify Student's ability to Differentiate or Project/Lab Analyse distinguish Distinguish Methodology Student's ability to Operate or Technical Presentation/ Apply use information Demonstrate Demonstration Student's ability to Understand Explain or Classify Presentation/Seminar explain the ideas Student's ability to Remember Define or Recall Quiz recall (or remember) GUIDELINES FOR STUDENTS Students should take equal responsibility for implementing the OBE. Some of the responsibilities (not limited to) for the students in the OBE system are as follows:  Students should be well aware of each UO before the start of a unit in every course.  Students should be well aware of each CO before the start of the course.  Students should be well aware of each PO before the start of the program.  Students should think critically and reasonably with proper reflection and action.  The learning of the students should be connected and integrated with practical and real-life consequences.  Students should be well aware of their competency at every level of OBE. ix  ABBREVIATIONS AND SYMBOLS List of Abbreviations General Terms Abbreviations Full form Abbreviations Full form AC Alternative Current HWR Half Wave Rectifier ASIC Application-Specific Integrated JFET Junction Field Effect Transistor Circuits BCD Binary Coded Decimal LED Light Emitting Diode BJT Bipolar Junction Transistor LSB Least Significant Bit CB Common Base Configuration LVDT Linear Variable Differential Transformer CC Common Collector MOSFET Metal Oxide Semiconductor Configuration Field Effect Transistor CD Diffusion Capacitance MSB Most Significant Bit CE Common Emitter PIV Peek Inverse Voltage Configuration CMOS Complementary Metal Oxide PMMC Permanent Magnet Moving Semiconductor Coil CMRR Common Mode Rejection RAM Random Access Memory Ratio D- MOSFET Depletion Metal Oxide RMS Root Mean Square Semiconductor Field Effect Transistor DC Direct Current ROM Read Only Memory E- MOSFET Enhancement Metal Oxide SCR Silicon Controlled Rectifiers Semiconductor Field Effect Transistor EEPROM Electrically Erasable SVRR Supply Voltage Rejection Ratio Programmable Read Only Memory FET Field Effect Transistor VLSI Very Large Scale Integration x  List of Symbols Symbols Description Symbols Description 𝑅 Static Resistance μ Amplification Factor 𝐶 Transition Capacitance 𝐼 Gate Cut-Off Current 𝐶 Diffusion or storage 𝑅 Input Resistance Capacitance η The Ratio or Efficiency 𝑔 Trans-Conductance 𝑅 Zener Resistance 𝐴 Feedback Amplifier 𝑉 Zener Voltage 𝑉 Signal Voltage 𝑃 max Maximum Power Dissipation 𝐼 Signal Current 𝐼 Zener Current 𝐼 Input Offset Current 𝐼 Collector Current 𝐼 Input Bias Current 𝐼 Emitter Current A Large Signal Voltage Gain S Stability Factor 𝑉 Common Mode Voltage S’ & S’’ Thermal Stability Factor 𝑉 Output Offset Voltage 𝐼 Drain to Source Current 𝑉 Input Offset Voltage 𝑉 Gate to Source Voltage 𝑅 Resistance of the Thermistor 𝑅 Drain Source Resistance 𝐺 Gauge Factors xi  LIST OF FIGURES Unit 1 Diode and Its Application Fig. 1.1 : P-N Junction with No bias condition 3 Fig. 1.2 : P-N Junction in reverse bias 4 Fig. 1.3 : P-N Junction in forward bias 4 Fig. 1.4 : The diode V-I characteristics 4 Fig. 1.5 : Basic structure of energy band diagram in semiconductor 5 Fig. 1.6 : Fermi level position in doped semiconductors 5 Fig. 1.7 : Band diagram before contact 5 Fig. 1.8 : Band diagram after contact(Ideal case) 6 Fig. 1.9 : (a) and (b) Intermediate steps of constructing the energy band diagram of a P-N 6 junction, (c) and (d) The complete band diagram Fig. 1.10 : Practical energy band diagram for a P-N junction 7 Fig. 1.11 : Energy band diagram under thermal equilibrium 8 Fig. 1.12 : Energy band diagram under external bias 8 Fig. 1.13 : P-N Junction in forward bias 9 Fig. 1.14 : P-N Junction with reverse bias 10 Fig. 1.15 : (a) A reverse-biased P-N junction, (b) band diagram without bias, and (c) energy 11 band under reverse bias Fig. 1.16 : (a) A forward-biased P-N junction, (b) band diagram without bias, and (c) energy 11 band under forward bias Fig. 1.17 : Depletion layer capacitance 12 Fig. 1.18 : Diode characteristics for different temperatures 14 Fig. 1.19 : A diode circuit 15 Fig. 1.20 : Switching timing of diode 16 xii Fig. 1.21 : Storage timing of diode 16 Fig. 1.22 : Block diagram of DC power supply 17 Fig. 1.23 : Half Wave Rectifier circuit and its output waveform 17 Fig. 1.24 (a) : Thevenin’s equivalent of Half wave rectifier 20 Fig. 1.24 (b) : Variation in terminal voltage with load current for ideal & practical power supply 20 Fig. 1.25 : A Centertap Full Wave Rectifier Circuit 22 Fig. 1.26 : Full Wave Bridge Rectifier Circuit 25 Fig. 1.26(a) : Inductor filter circuit 27 Fig. 1.26(b) : Output of inductor filter 27 Fig. 1.27 : Output waveform of an inductor filter 29 Fig. 1.28 : Capacitor filter circuit 29 Fig. 1.29 : Output of capacitor filter 30 Fig. 1.30 : Zener diode as a voltage regulator 31 Fig. 1.31 : Band diagram of Zener breakdown 33 Fig. 1.32 : I-V characteristics of Zener and Avalanche Breakdown 34 Fig. 1.33 : A practical diode under DC operating conditions 35 Fig. 1.34(a) : Forward biased DC diode model 35 Fig. 1.34(b) : Reverse biased DC diode model 35 Fig. 1.35 : Reverse biased ac diode model 36 Fig. 1.36 : Forward biased ac diode model 36 Fig. 1.37 : Diode as a switch 37 Fig. 1.38 : Symbol and circuit diagram of a LED 37 Fig. 1.39 : Symbol and I-V Characteristics of a Zener diode 38 Fig. 1.40 : The details of a photo diode 39 Fig. 1.41 : V-I Characteristics of a photo diode 39 Fig. 1.42 : (a) SCR symbol; (b) basic construction 40 xiii Fig. 1.43 : Two transistor terminology of a SCR 41 Fig. 1.44 : “Off” state of the SCR 41 Fig. 1.45 : “On” state of the SCR 42 Fig. 1.46 : SCR characteristics 42 Unit 2 Transistor Characteristics Fig. 2.1 : Construction of BJT-PNP & NPN 53 Fig. 2.2 : Depletion Region and Barrier Potential 55 Fig. 2.3 : Transistor Operation (NPN) 56 Fig. 2.4 : Transistor Operation (PNP) 57 Fig. 2.5 : Common Base Configuration 57 Fig. 2.6 : 𝐼 In CB Configuration 58 Fig. 2.7 : Common Emitter Configuration 58 Fig. 2.8 : Common Collector Configuration 59 Fig. 2.9 : Circuit under consideration 60 Fig. 2.10 : DC Load Line 60 Fig. 2.11 : Potential divider bias 62 Fig. 2.12 : Self bias circuit 64 Fig. 2.13 : Thermistor bias Compensation 64 Fig. 2.14 : Sensistor bias Compensation 65 Fig. 2.15 : Transistor as Amplifier 65 Fig. 2.16 : Construction and symbol of an (a) n- channel and (b) p-channel JFET 67 Fig. 2.17 : N-Channel FET with applied drain voltage polarities 67 Fig. 2.18 : The rise in depletion width with applied 𝑉 ( 𝑉 ) 68 Fig. 2.19 : Depletion Region development due to internal voltage drop 68 Fig. 2.20 : Pinch-off occurs at 𝑉 =𝑉 70 xiv Fig. 2.21 : Output Characteristics 70 Fig. 2.22 : Construction and symbol of a D-MOSFET 72 Fig. 2.23 : Operation of a D-MOSFET at 𝑉 =0 72 Fig. 2.24 : Operation of a D-MOSFET at 𝑉 =negative 73 Fig. 2.25 : Operation of a D-MOSFET at 𝑉 =positive 73 Fig. 2.26 : The drain –source characteristics and transfer characteristics 74 Fig. 2.27 : Symbol of a p-channel D-MOSFET 75 Fig. 2.28 : Construction and symbol of an E-MOSFET 75 Fig. 2.29 : Drain Source Characteristics 76 Fig. 2.30 : Basic CMOS configuration 77 Fig. 2.31 : Symbol of an NMOS and PMOS transistor 77 Fig. 2.32 : CMOS using Pull up and Pull Down 78 Fig. 2.33 : CMOS Inverter 79 Unit 3 Feedback Amplifier and Oscillators Fig. 3.1 : A single-loop feedback system 91 Fig. 3.2 : Mixer Networks: (a) Voltage Comparator (b) Current Comparator 92 Fig. 3.3 : Sampling Networks: (a) Voltage Sampling (b) Current Sampling 92 Fig. 3.4 : Feedback amplifiers connection type: (a) Voltage series feedback (b) Current 93 series feedback (c) Current-shunt feedback d) Voltage-shunt feedback Fig. 3.5 : Voltage series feedback connection 95 Fig. 3.6 : Voltage-shunt feedback connection 95 Fig. 3.7 : Current-Series feedback connection 97 Fig. 3.8 : Effect of negative feedback on gain and bandwidth 98 Fig. 3.9 : Difference between amplifier and oscillator 99 Fig. 3.10 : Tank circuit ( LC-tuned circuit) 99 xv Fig. 3.11 : Charging of an Inductor 99 Fig. 3.12 : Discharging of an Inductor 100 Fig. 3.13 : Damped Sinusoidal waveform 100 Fig. 3.14 : Block diagram of positive feedback amplifier 101 Fig. 3.15 : Oscillator classification chart 103 Fig. 3.16 : RC phase shift oscillator 104 Fig. 3.17 : A Wien Bridge Oscillator 105 Fig. 3.18 : Circuit diagram of Hartley oscillator 106 Fig. 3.19 : Circuit diagram of Colpitts oscillator 107 Fig. 3.20 : Electrical equivalent circuit of crystal 108 Fig. 3.21 : Transistorized crystal oscillator 108 Fig. 3.22 : Wien Bridge oscillator circuit 110 Unit 4 Operational Amplifier and Application Fig. 4.1 : Block diagram of Op-Amp 116 Fig. 4.2 : Symbol of Op-Amp 117 Fig. 4.3 : Pin configuration of IC 741 Op-Amp 117 Fig. 4.4 : Op-Amp equivalent circuit 118 Fig. 4.5 : Op-Amp equivalent circuit for an ideal case 118 Fig. 4.6 : Circuit arrangement for calculation of offset voltage 119 Fig. 4.7 : Op-Amp inverting amplifier 120 Fig. 4.8 : Open loop inverting amplifier 121 Fig. 4.9 : Open-loop non-inverting amplifier 122 Fig. 4.10 : Differential amplifier using OP-Amp 122 Fig. 4.11 : Non-Inverting Amplifier with Feedback 123 Fig. 4.12 : Equivalent circuit for input impedance calculation 124 xvi Fig. 4.13 : Equivalent circuit for output impedance calculation 125 Fig. 4.14 : Inverting Amplifier with feedback 126 Fig. 4.15 : Voltage follower circuit 126 Fig. 4.16 : Op-Amp as an Inverter 127 Fig. 4.17 : Op-Amp as Current to voltage converter 127 Fig. 4.18 : Inverting summing amplifier 128 Fig. 4.19 : Non-inverting summing amplifier 129 Fig. 4.20 : Op-Amp as a Subtractor 131 Fig. 4.21 : Op-Amp Integrator circuit 132 Fig. 4.22 : Op-Amp differentiator circuit 133 Fig. 4.23 : Input and Output waveform of a Differentiator 133 Fig. 4.24 : Ideal filter response 134 Fig. 4.25 : (a) A first-order low pass filter (b) Filter response 134 Fig. 4.26 : (a) Second order Low pass filter (b) Filter response 135 Fig. 4.27 : (a) First order High pass filter (b) Filter response 135 Fig. 4.28 : (a) Second order High pass filter (b) Filter response 136 Fig. 4.29 : A bandpass active filter 136 Unit 5 Measuring Instruments & Transducers Fig. 5.1 : Construction of D’ Arsonval Instrument 159 Fig. 5.2 : Instrument for Permanent Magnet Moving Coil (PMMC) 160 Fig. 5.3 : Ohmmeter 162 Fig. 5.4 : A series ohmmeter 163 Fig. 5.5 : Scale of a series ohmmeter 163 Fig. 5.6 : (a) Shunt type ohmmeter (b) Scale of a shunt ohmmeter 164 Fig. 5.7 : Multirange Ohmmeter 165 xvii Fig. 5.8 : Galvanometer 165 Fig. 5.9 : Concept of a potentiometer 167 Fig. 5.10 : Potentiometer 168 Fig. 5.11 : A rotary potentiometer 168 Fig. 5.12 : Construction of a moving iron frequency meter 169 Fig. 5.13 : Construction of an Electrodynamic frequency meter 170 Fig. 5.14 : Types of Thermistors 179 Fig. 5.15 : Resistance-Temperature characteristics 179 Fig. 5.16 :The construction of LVDT 181 Fig. 5.17 : Hall Effect element 184 Fig. 5.18 : Parallel plate capacitive transducer 186 Fig. 5.19 : Variation in the distance between two plates 187 Fig. 5.20 : Capacitance between two plates 188 Fig. 5.21 : Piezoelectric transducer 190 Fig. 5.22 : Construction of a seismic transducer 192 Unit 6 Introduction to Digital Electronics Fig. 6.1 : Illustration of 9’s complement arithmetic 206 Fig. 6.2 : Illustration of 10’s complement arithmetic 207 Fig. 6.3 : A Two-input OR gate and its truth table 233 Fig. 6.4 : A Two-input AND gate and its truth table 234 Fig. 6.5 : Symbol of a NOT gate and its truth table 234 Fig. 6.6 : A Two-input Ex-OR gate 235 Fig. 6.7 : A Two-input NAND gate and its truth table 235 Fig. 6.8 : A Two-input NOR gate and its truth table 236 Fig. 6.9 : A Two-input Ex-NOR gate and its truth table 236 xviii Fig. 6.10 : NAND gate as a Universal gate 237 Fig. 6.11 : NOR gate as a Universal gate 237 Fig. 6.12 : A combinational logic 240 Fig. 6.13 : Classification of Combination Logic 241 Fig. 6.14 : Sequential logic 242 xix  LIST OF TABLES Unit 1 Diode and Its Application Table. 1.1 : Comparison of Zener and Avalanche Breakdown 34 Unit 3 Feedback Amplifier and Oscillators Table. 3.1 : Summary of Gain, Feedback, and Gain with feedback from Fig.3.4 94 Table. 3.2 : Summarizes the effect of feedback on input and output impedance. 97 Unit 5 Measuring Instruments & Transducers Table. 5.1 :Key difference between a sensor and a transducer 172 Table. 5.2 : Gauge Factor 177 Unit 6 Introduction to Digital Electronics Table. 6.1 : Octal to Binary Conversion 215 Table. 6.2 : Hexadecimal to Binary Conversion 222 Table. 6.3 : BCD code representations 224 Table. 6.4 : Excess-3 code for the decimal numbers 226 Table. 6.5 : Gray code 227 Table. 6.6 : Comparison between the Combinational and Sequential Logic Circuits 243 xx  CONTENTS Foreword iv Acknowledgment v Preface vi Outcome Based Education vii Course Outcomes viii Guidelines for Teachers ix Guidelines for Students x Abbreviations and Symbols x List of Figures xii List of Tables xx Unit 1: Diode and Its Applications 1-50 Rationale 1 Unit Outcomes 1 Learning Objective 1 Mapping the unit outcome with course outcomes 2 1.1 Review of a P-N junction 3 1.2 The V-I Characteristics 3 1.3 Semiconductor band and Fermi energy levels 5 1.3.1 Position of Fermi level in doped Semiconductors 5 1.3.2 Energy Band Diagram for a P-N junction 5 1.3.3 Built-in voltage of the P-N junction 6 1.4 P-N Junction with external bias 7 1.4.1 Zero bias voltage 7 1.4.2 Forward bias condition 8 1.4.3 Energy band diagrams for P-N junction with external bias 11 1.5 Static and dynamic resistance of a P-N junction diode 11 1.6 Diode capacitance 12 1.7 Temperature Effect on Diode 14 1.8 Switching time of a Diode 15 1.9 DC Power Supply 16 Solved Examples 43 Exercises Questions 45 Self-Study Questions 45 Multiple Choice Questions 46 Attainment & Gap Analysis 50 Unit 2: Transistor Characteristics 51-88 Rationale 50 Unit Outcomes 50 xxi  Learning Objective 50 Mapping the unit outcome with the course outcomes 50 2.1 Bipolar Junction Transistor ( BJT) 53 2.2 Modes (Regions) of operation of BJT 54 2.3 Transistor operation in linear mode 55 2.3.1 For NPN transistor 55 2.3.2 For PNP transistor 56 2.4 Transistor Configuration 57 2.4.1 Common Base Configuration (CB) 57 2.4.2 Common Emitter Configuration(CE) 58 2.4.2 Common Collector Configuration(CC) 59 2.5 DC Load Line 59 2.6 Transistor biasing 61 2.7 Thermal Stability 63 2.7.1 Generalized Expression for S 63 2.7.2 Bias Compensation 64 2.8 Transistor as Amplifier 65 2.9 The Field Effect Transistor (FET) 66 2.9.1 Junction Field effect transistors (JFET) 66 2.9.2 Operation of a JFET (n-channel) 67 2.9.3 FET Parameters 70 2.9.4 Comparison between BJT and FET 71 2.10 MOSFET (Metal oxide semiconductor field effect transistor) 71 2.10.1 D-MOSFET (n-channel) 72 2.10.2 E-MOSFET (n-channel) 75 2.11 CMOS 77 Solved Example 80 Exercises Questions 83 Self-Study Questions 84 Multiple Choice Questions 84 Attainment & Gap Analysis 88 Unit 3: Feedback Amplifier and Oscillators 89-113 Rationale 89 Unit Outcomes 89 Learning Objective 89 Mapping the unit outcome with the course outcomes 89 3.1 The concept of feedback 91 3.2 Feedback connection types 93 3.3 The gain with feedback 94 3.4 Input Impedance with feedback 95 3.5 Output Impedance with feedback 96 3.6 General characteristics of a negative feedback amplifier 97 3.7 Oscillators 99 3.8 Block Diagram of Positive Feedback Amplifier 101 3.9 Classification of Oscillator 102 xxii 3.10 RC phase shift oscillator 103 3.11 Wien Bridge Oscillator 105 3.12 LC Oscillator 106 3.12.1 Hartley Oscillator 106 3.12.2 Colpitts Oscillator 107 3.12.3 Crystal Oscillator 107 Solved Example 109 Exercises Questions 110 Self-Study Questions 110 Multiple Choice Questions 111 Attainment & Gap Analysis 113 Unit 4: Operational Amplifier and Applications 114-155 Rationale 114 Unit Outcomes 114 Learning Objective 114 Mapping the unit outcome with the course outcomes 114 4.1 General characteristics of an Op-Amp 116 4.2 Important Specification of Op-Amp 118 4.3 Concept of Virtual ground 120 4.4 Open Loop configuration of an Op-Amp 121 4.4.1 Inverting Amplifier 121 4.4.2 Non-Inverting Amplifier 121 4.4.3 Differential Amplifier 122 4.5 Close loop Configurations of an Op-Amp 122 4.5.1 Non-Inverting Amplifier with Feedback 123 4.5.2 Inverting Amplifier with Feedback 125 4.5.3 Buffer Amplifier or Voltage Follower 126 4.5.4 Inverter ( Sign Changer) 127 4.5.5 Current to voltage converter 127 4.6 Application of Op-Amp 128 4.6.1 Summing, Scaling, and Averaging Amplifiers 128 4.6.2 OP-Amp as an Subtractor 130 4.6.3 OP-Amp as an Integrator 131 4.6.4 OP-Amp as Differentiator 132 4.7 Active Filter using Op-Amp 134 4.7.1 Low pass filter 134 4.7.2 High pass Active filter 135 4.7.3 High pass Active filter 136 Solved Example 136 Exercises Questions 149 Self-Study Questions 151 Multiple Choice Questions 151 Attainment & Gap Analysis 155 xxiii Unit 5: Rotational Motion 156-201 Rationale 156 Unit Outcomes 156 Learning Objective 156 Mapping the unit outcome with the course outcomes 156 5.1 D’ Arsonval Movement 159 5.2 Permanent Magnet Moving Coil Instrument 160 5.3 Ohmmeter 162 5.3.1 Series Ohmmeter 163 5.3.2 Shunt Ohmmeter 164 5.3.3 Multi range Ohmmeter 164 5.4 Galvanometer 165 5.5 Potentiometer 167 5.6 Frequency Meters 169 5.6.1 Moving Iron Frequency Meter 169 5.6.2 Electrodynamic Frequency Meter 170 5.6.3 Vibrating-reed Frequency Meter 171 5.7 Sensors and Transducers 170 5.7.1 Electrical Transducers 172 5.7.2 Characteristics of a Transducers 173 5.7.3 Factor influencing the choice of transducers 173 5.7.4 Classification of Transducer 174 5.8 Strain Gauges 175 5.9 Thermistors 177 5.10 Liner variable differential transformer (LVDT) 180 5.11 Hall Effect Transducer 183 5.12 Capacitive Transducer 185 5.13 Piezoelectric Transducer 5.14 Seismic Transducer 189 Solved Example 191 Exercises Questions 193 Multiple Choice Questions 196 Attainment & Gap Analysis 197 201 Unit 6: Introduction to Digital Electronics 202-253 Rationale 202 202 Unit Outcomes 202 Learning Objective 203 Mapping the unit outcome with the course outcomes 204 6.1 The number system 205 6.1.1 Decimal Number System 208 6.1.2 Binary Number System 208 6.1.3 Octal Number System 208 6.1.4 Hexadecimal Number System 209 6.2 Number Representation in Binary System 209 6.2.1 Sign-Bit Magnitude 209 xxiv 6.3 The Decimal Equivalent 211 6.3.1 Binary-to-Decimal Conversions 211 6.3.2 Octal-to-Decimal Conversions 211 6.3.3 Hexadecimal-to-Decimal Conversions 211 6.3.4 Decimal-to-Binary Conversions 211 6.3.5 Decimal-to-Octal Conversions 212 6.3.6 Decimal-to-Hexadecimal Conversions 213 6.3.7 Binary-Octal and Octal-Binary Conversions 214 6.3.8 Binary-Hex and Hex-Binary Conversions 218 6.3.9 Hex-Octal and Octal-Hex Conversions 223 6.4 Binary Codes 224 6.4.1 Binary Coded Decimal (BCD) 224 6.4.2 Excess-3 Code 226 6.4.3 Gray Code 227 6.5 The Digital Arithmetic 230 233 6.6 The Logic Gates 233 6.6.1 The OR Gate 234 6.6.2 The AND Gate 234 6.6.3 The NOT Gate 234 6.6.4 The EXCLUSIVE-OR Gate 235 6.6.5 The NAND Gate 236 6.6.6 The NOR Gate 236 6.6.7 The EXCLUSIVE-NOR Gate 236 6.6.8 The Universal Gates 236 6.7 The Boolean algebra 237 6.8 The Digital Circuits 239 6.8.1 The Combinational Circuits 239 6.8.2 The Sequential Circuits 241 Solved Example 244 Exercises Questions 248 Self-Study Questions 249 Multiple Choice Questions 250 Attainment & Gap Analysis 253 References for Further Learning 255 CO and PO Attainment Table 256 Index 257 xxv  1. Diode and Its Applications RATIONALE It is now more than 80 years since the first P-N junction was introduced. Since then, it becomes an integral part of the majority of IC designs. In this chapter, we will study the details of a semiconductor diode, the construction and working principles of a few advanced and application-oriented diodes. UNIT OUTCOMES U1-O1: Unit-1 Learning Outcome-1 To know about the basic operation of a P-N junction diode, its breakdown mechanism, equivalent circuits, and loadline analysis. U1-O2: Unit-1 Learning Outcome-2 To know about the construction and operation of different types of rectifiers and different breakdown mechanisms of the P-N junction diodes. U1-O3: Unit-1 Learning Outcome-3 To know the operation and applications of a Zener diode, opto-electronic devices such as LEDs and photo-diode, and SCR. LEARNING OBJECTIVES LO1: Study of fundamentals of a P-N junction diode; ideal versus practical. LO2: Importance of Diode equivalent circuits, their resistance levels, and load line analysis. LO3: Working of a diode as a switch. LO4: Study of construction and operation of half-wave and full-wave rectifiers; with and without filters. LO5: Importance of breakdown mechanism. LO6: operation and applications of a Zener diode, various opto-electronic devices such as LEDs and photo-diode, SCR. 1  MAPPING THE UNIT OUTCOMES WITH THE COURSE OUTCOMES EXPECTED MAPPING WITH COURSE OUTCOMES Unit (1- Weak Correlation; 2- Medium correlation; 3- Strong Correlation) Outcome CO-1 CO-2 CO-3 CO-4 CO-5 CO-6 CO-7 U1-O1 3 3 -- -- -- -- -- U1-O2 3 3 -- -- -- -- -- U1-O3 3 3 -- -- -- -- -- Interesting Facts: 1. In 1939, Russell Ohl of Bell Laboratories discovers the P-N junction and photovoltaic effects in silicon that lead to the development of junction transistors and solar cells. 2. A semiconductor is made using materials such as silicon, germanium, and gallium arsenide. These materials are also used to make P-N junction diodes. Silicon is used over germanium when creating these junction diodes. 3. Photodiodes are special P-N junction diodes operated in reverse bias. They are mainly designed for detecting optical signals. Video Resources: Sr Title URL QR Code 1. Semiconductor: P- https://www.youtube.com/watch?v=6dU Type and N-Type, pV2ovqog Intrinsic and Extrinsic 2. PN Junction Diode https://www.youtube.com/watch?v=o- and V-I Rya9KZYY4 Characteristics 3. Rectifier Operation https://www.youtube.com/watch?v=5cb QNfO0Mwg 4. What is a Zener https://www.youtube.com/watch?v=Xh Diode QqtdTlRus 5. What is https://www.youtube.com/watch?v=8k9 Photodiode UIlwo7W4 6. Light Emitting https://www.youtube.com/watch?v=wl4 Diode (LED) 5Rrt4j2U Working Principle 7. SCR https://www.youtube.com/watch?v=RJ4 3fnX-LsM 2 1.1 Review of a P-N junction There are two types of extrinsic semiconductors. Extrinsic semiconductors with a more significant electron concentration than hole concentration are known as N-type semiconductors. The phrase 'N-type' comes from the negative charge of the electron. In N-type semiconductors, electrons are the majority carriers, and holes are the minority carriers. N-type semiconductors are created by doping an intrinsic semiconductor with donor impurities. In an N-type semiconductor, the Fermi energy level is greater than that of the intrinsic semiconductor and lies closer to the conduction band than the valence band. Arsenic has five valence electrons; however, only 4 of them form part of covalent bonds. The 5th electron is then free to take part in conduction. The electrons are said to be the majority carriers, and the holes are the minority carriers. The P-type semiconductors have a more significant hole concentration than electron concentration. The phrase 'P-type' refers to the positive charge of the hole. In P-type semiconductors, holes are the majority carriers, and electrons are the minority carriers. P-type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities. P- type semiconductors have Fermi energy levels below the intrinsic Fermi energy level. The Fermi energy level lies closer to the valence band than the conduction band in a P-type semiconductor. For example, gallium has three valence electrons; however, there are four covalent bonds to fill. The 4th bond, therefore, remains vacant, producing a hole. The holes are said to be the majority carriers, and the electrons are the minority carriers. When P–type, and N–type materials come in close contact, electrons start diffusing from N-type material into P-material. At the same time, holes also begin to diffuse from P-type material into N-material. Every electron transfers a negative charge (-q) onto the P-side and leaves an uncompensated (+q) charge of the donor on the N-side. Every hole creates one positive charge (q) on the N-side and (-q) on the P-side. A negative charge prevents electrons from further diffusion, and a Positive charge stops holes from further diffusion. The diffusion forms a dipole charge layer at the P-N junction interface. It is called a potential barrier, as shown in Fig 1.1. There is a "built-in" voltage at the P-N junction interface that prevents penetration of electrons into the P-side and holes into the N-side. Fig. 1.1: P-N Junction with no bias condition 1.2 The V-I Characteristics The polarity in Fig. 1.2 attracts the holes to the left and the electrons to the right. According to the current continuity law, the current can only flow if all the charged particles form a closed loop. However, there are very few holes in the N-type material and few electrons in the P-type material. Therefore, very few carriers are available to support the current through the junction plane. For the voltage polarity shown, the current is nearly zero. 3  Fig. 1.2: P-N Junction in reverse bias Fig.1.3: P-N Junction in forward bias The polarity shown in Fig. 1.3 attracts electrons to the left and holes to the right. There are plenty of electrons in the N-type material and plenty of holes in the P-type material. Therefore, there are a lot of carriers available to cross the junction. When the voltage applied is lower than the built-in voltage, the current is approximately zero. When the voltage exceeds the built-in voltage, the current can flow through the P-N junction. The semiconductor diode consists of a P-N junction with two contacts attached to the p and n sides. The complete current equation of the P-N junction diode is given below- 𝑞𝑉 𝐼 𝐼 exp 1 𝑘𝑇 𝑘 is Boltzmann constant 𝑇 is the temperature in 𝐾 At room temperature 𝑇 300𝐾 , 0.026 𝑉 𝐼 is a saturation current, typically 𝐼 is in the range of 𝐼 10 to 10 𝐴 When the voltage V is negative ("reverse" polarity), the exponential term 1; The diode current is 𝐼 (very small). When the voltage V is positive ("forward" polarity), the exponential term increases rapidly with V, and the current is high. Fig. 1.4: The diode V-I characteristics 4 1.3. Semiconductor band and Fermi energy levels Fermi energy 𝐸 is the average energy of all the free carriers in a sample. In equilibrium, the Fermi energy must be uniform over the semiconductor (compared to the temperature distribution over any sample in equilibrium). Fig. 1.5 shows the basic structure of the energy band diagram in a semiconductor. Fig. 1.5: Basic structure of energy band diagram in semiconductor 1.3.1. Position of Fermi level in doped semiconductors In an intrinsic semiconductor, the Fermi level lies precisely at the center of the band gap. While in the extrinsic semiconductor Fermi level will not be in the center. It is close to the conduction band in N-type and the valance band in P-type. Fig. 1.6 shows the Fermi level position in doped semiconductors. Intrinsic Semiconductor Donor-doped semiconductor (N-type) Acceptor doped semiconductor (P-type) 𝑛 𝑝 𝑛 𝑛" 𝑝 𝑝" 𝑛 𝐸 ~ 𝐸 𝐸 /2 𝐸 ~𝐸 𝐸 ~𝐸 Fig.1.6: Fermi level position in doped semiconductors 1.3.2. Energy Band Diagram for a P-N junction The energy band diagram for the junction can be understood as shown in Fig. 1.7. 1. Two separate bits of semiconductor first is N-type, the other is P-type 2. When bits are joined together: not in equilibrium 𝐸 𝑛 𝐸 𝑝 Fig. 1.7: Band diagram before contact 3. This state is unstable regarding its energy (once n and p are in contact). On the N-side, there are many electrons in the conduction band, and on the P-side, there are many holes in the valence band. Thus, due to the concentration gradient, charge carriers will flow from higher to lower concentrations. One needs to consider the flow of both electrons and holes. 5  Electrons close to the interface flow from n to the p side, and holes close to the interface flow from p to the n side. This flow continues until Fermi levels equilibrate. The balance is achieved by electrons diffusing into a P-side (bringing an extra negative charge) and by the holes diffusing into an N-side (carrying an additional negative charge). These recombinations grow a layer on both sides of the barrier depleted of free carriers. Thus, the band diagram after contact, i.e., after the achievement of the equilibrium, is shown in the figure. Fig. 1.8: Band diagram after contact ( Ideal case) Fig. 1.9 depicts the energy band diagram for the P-N junction. (a) (b) (c) (d) Fig.1.9: (a) and (b) Intermediate steps of constructing the energy band diagram of a P-N junction, (c) and (d) The complete band diagram. 1.3.3. Built-in voltage of the P-N junction Consider the practical energy band diagram of a P-N junction as shown in Fig. 1.10 6  Fig. 1.10: Practical energy band diagram for a P-N junction Far from the junction, on the N-side, 𝑛 𝑁 , at any arbitrary point 𝑥 inside the transition region (between 𝑥 and 𝑥 ); 𝑛 𝑥 𝑁 𝑒 where 𝜙 𝑥 is the potential barrier at the point 𝑥 At the point located far in the p-region, the potential barrier flattens out and reaches 𝜙 ; at this point: 𝑛 𝑁 𝑒 On the other hand, for the point in the p-material: 𝑛 𝑛 𝑁 𝑒 𝑁 From this, the built potential barrier, i.e., the energy barrier, in joules or 𝑒𝑉 𝑁 𝑁 𝜙 𝑘𝑇. ln 𝑛 The voltage corresponding to the energy barrier 𝜙 𝑉 𝑞 𝑘𝑇 𝑁 𝑁 ⟹𝑉. ln 𝑞 𝑛 1.4. P-N Junction with external bias To understand the behavior of a P-N junction under external bias, two conditions, namely working under zero applied voltage and working with the application of the external bias, need to be considered. 1.4.1. Zero bias voltage Fig. 1.11 shows the band diagram under thermal equilibrium for a P-N junction. 7  Fig. 1.11: Energy band diagram under thermal equilibrium We know the n- side has electrons as the majority of charge carriers, and the P-type has holes as the majority of charge carriers. Thus, away from the depletion region, the N-side supplies free electrons (𝑛 large) (majority) and P-side supplies free holes (𝑝 large) (majority). As the holes are minority charge carriers on the N-side and electrons are minority charge carriers on the P-side, we get a small concentration 𝑛 of free electrons on the P-side (minority) and a small concentration 𝑝 of free holes on the N-side (minority). Potential drop VB across the junction (with zero applied bias) can be given as- 𝑛 𝑝 𝑒𝑉 exp 𝑛 𝑝 𝑘𝑇 1.4.2. Forward bias condition When the external bias voltage 𝑉 is applied, equilibrium is disturbed, as shown in Fig. 1.12. Fig. 1.12 Energy band diagram under external bias 8 1.4.2.1. Forward Bias: Electrons in the P-type material, near the positive terminal of the supply, break their electron pair bonds and enter the supply, thereby producing new holes. Electrons from the supply's negative terminal enter the N-type material and migrate toward the junction. Free electrons from the N-type material flow across the junction and move into the holes migrated from the positive terminal. This current flow will continue as long as the external bias is connected, known as the forward current flow. In forward bias, the potential drop across the junction is reduced. Fig.1.13 shows the forward bias condition of the P-N junction diode. Fig. 1.13 P-N Junction in forward bias If 𝑉 is the potential drop across the junction, then we can write 𝑛 𝑝 𝑒𝑉 𝑒𝑥𝑝 𝑛 𝑝 𝑘𝑇 We have that 𝑉 𝑉 𝑉 Hence 𝑛 𝑝 𝑒𝑉 𝑒𝑉 𝑒𝑥𝑝 𝑒𝑥𝑝 … … …. 1 𝑛 𝑝 𝑘𝑇 𝑘𝑇 For zero applied bias- 𝑛 𝑝 𝑒𝑉 𝑒𝑥𝑝 …………… 2 𝑛 𝑝 𝑘𝑇 By equations and , we get- 𝑛 𝑛 𝑒𝑉 𝑒𝑥𝑝 𝑛 𝑛 𝑘𝑇 𝑝 𝑝 𝑒𝑉 𝑒𝑥𝑝 𝑝 𝑝 𝑘𝑇 where, 𝑛 is large - plenty of free electrons on N-side 9  𝑝 is large - plenty of free holes on P-side They change marginally with the application f the bias voltage. i.e. 𝑛  𝑛 ; 𝑝  𝑝 𝑛 𝑝 𝑒𝑉 𝑒𝑥𝑝 𝑛 𝑝 𝑘𝑇 Thus, 𝐼 𝐼 exp 1 1.4.2.2. Reverse Bias: When the polarity of the supply is reversed, the free electrons in the N-type are attracted towards the positive terminal, away from the junction, while the electrons from the negative terminal of the supply enter the P-type and migrate towards the junction. As a result, the depletion layer becomes wider. The current flow is minimal and is called reverse current. It is to be noted that minority carriers produce this current, and the device is said to be reverse-biased. Fig. 1.14 shows the reverse biased P-N junction. Fig. 1.14. P-N Junction with reverse bias In reverse bias, the potential drop across the junction is increased. Here current equation is given as- 𝑒𝑉 𝐼 𝐼 1 exp 𝑘𝑇 Thus, in summary, the I-V characteristics of the P-N junction diode are- 𝑒𝑉 ⟹ 𝐼 𝐼 exp 1 Forward bias 𝑘𝑇 𝑒𝑉 ⟹ 𝐼 𝐼 1 exp Reverse bias 𝑘𝑇 Since the exponential term is minimal due to negative voltage, it is approximately equal to 𝐼. 10 1.4.3. Energy band diagrams for P-N junctions with external bias (a) (a) (b) (b) (c) (c) Fig. 1.15: (a) A reverse–biased P-N junction, Fig. 1.16: (a) A forward-biased P-N junction, (b) band diagram without bias, and (c) (b) band diagram without bias, and (c) energy band under reverse bias. energy band under forward bias. 1.5. Static and dynamic resistance of a P-N junction diode It is always necessary to remember that no diode can act as an ideal diode. An actual diode does not behave as a perfect conductor when forward–biased and an excellent insulator when reverse- biased. It neither offers zero resistance when forward-biased nor infinite resistance when reverse- biased. Generally, in a P-N junction diode, there are two types of resistance that are considered as- 1. Static resistance(RD): Static resistance of a P-N junction diode is calculated when the diode is connected to a DC circuit. This resistance is also known as DC resistance or static resistance. It is the ratio of DC voltage across the diode to the DC flowing through it. It is denoted by 𝑅. 𝑉 𝑅 𝐼 2. Dynamic resistance: Dynamic resistance of a P-N junction diode is defined as the resistance offered by the diode to the AC signal. It is also known as AC resistance. The 11  ∆ dynamic resistance of a diode is equal to the slope of 𝑉- 𝐼 characteristics 𝑜𝑟 of the ∆ diode. i.e., Change in voltage 𝑑𝑉 ∆𝑉 r Resulted change in current 𝑑𝐼 ∆𝐼 Consider the diode current equation 𝐼 𝐼 𝑒 1 Differentiating the equation to 𝑉, we get dynamic conductance as- 𝑑𝐼 𝐼 𝑒 𝑔 𝑑𝑉 𝜂𝑉 𝐼 𝐼 ⟹𝑔 𝜂𝑉 𝜂𝑉 ⟹𝑟 𝐼 𝐼 For a 𝜙 reverse biased junction 𝑖. 𝑒., "𝑔. 𝑔 is extremely small, and 𝑟 is very large. On the other hand, for a forward-biased junction 𝐼 𝐼. So the equation of 𝑟 becomes 𝜂𝑉 𝑟 𝐼 From the above expression, it is clear that dynamic resistance is inversely proportional to the forward-biased junction current. 1.6. Diode capacitance There are usually two types of diode capacitance as- 1. Depletion layer capacitance or transition capacitance 𝑪𝑻 : The formation of a P-N junction gives rise to the formation of the depletion layer on either side of the junction. Since this capacitance is formed in the junction area, it is also called space charge capacitance. This capacitance arises due to immobile charges at the junction varying with the applied voltage, called the junction capacitance. Fig. 1.17 shows the formation of depletion layer capacitance. 12  Fig. 1.17: Depletion layer capacitance The capacitance of a parallel plate capacitor is given as- 𝜖 𝐴 𝐶 𝑑 Where 𝜖 is the permittivity of dielectric (insulator) between the plate of area 𝐴 separated by a distance 𝑑. Since the depletion layer width 𝑑 increases with the increase in reverse bias voltage, the resulting depletion layer capacitance will decrease with the increased reverse bias. The depletion layer capacitance depends upon the nature of a P-N junction, semiconductor material, and the magnitude of the applied reverse voltage and is given as - 𝐶 𝐶 𝑉 1 𝑉 Where 𝐶 Capacitance at zero bias condition 𝑉 Applied reverse voltage 𝑉 Volt equivalent of temperature ⎧1 for a step or abrupt alloy junction ⎪2 𝜂 ⎨1 ⎪ for linear graded junction or diffused junction ⎩3 It is evident from the above equations that the value of depletion layer capacitance 𝐶 can be controlled by varying the applied reverse voltage. This property of variable capacitance, possessed by a reverse biased P-N junction, is used in constructing a device called varicap or varactor for FM circuits. The range of depletion layer capacitance is approximately in 𝑛𝐹(nanofarad). 2. Diffusion or storage capacitance 𝑪𝑫 The capacitance in a forward-biased junction is called diffusion or storage capacitance. It is different from the depletion layer capacitance in a reverse-biased junction. The diffusion capacitance arises due to the arrangement of minority carrier density. The value of diffusion capacitance is much larger than the depletion layer capacitance 𝑖. 𝑒., 𝐶 "𝐶. The following expression provides its value for abrupt junction: 𝜏. 𝐼 𝐶 𝜂. 𝑉 13  Where 𝜏 Lifetime of the carriers 𝐼 Forward current 𝑉 Volt equivalent of temperature 1 for 𝐺𝑒 𝜂 constant 2 for 𝑆𝑖 It is clear from the equation that the diffusion capacitance is directly proportional to the forward current 𝐼. Consider a forward-biased P-N junction carrying a current of 𝐼 amperes through it. Suppose the junction is suddenly reverse-biased. It caused the forward current to reduce quickly to zero. But it leaves several majority charge carriers stored within the depletion region. This charge represents a stored charge in the reverse biased condition and must be removed from the space charge region. The removal of stored charge takes a finite time. It represents an effect similar to the discharging of a capacitor. Thus the quantity of the stored charge represents the magnitude of diffusion capacitance. It noted that the impact of diffusion capacitance is negligible for a reverse-biased P-N junction. 1.7. Temperature Effect on Diode Fig. 1.18 shows the effect of temperature on diode characteristics. Fig. 1.18: Diode characteristics for different temperatures A-B curve: This curve shows diode characteristics for different temperatures in the forward bias. It is evidenced from Fig.1.18 that the curve moves towards the left with the increase in the temperature. It indicates that the conductivity of semiconductors increases with an increase in temperature. The intrinsic concentration (𝑛 ) of the semiconductors is dependent on temperature as given by: 𝑛 𝐾𝑇 𝑒 where 𝐸𝑔 the energy gap 𝐾 = a voltage man constant 𝑇 = a constant independent of temperature 14 When the temperature is high, the electrons of the outermost shell take the thermal energy and become free. So conductivity increases with temperature. Hence with an increase in temperature, the A-B curve would shift towards the left, i.e., the curve would rise sharply, and the breakdown voltage would also decrease with an increase in temperature. A-C curve: This curve shows diode characteristics in the reverse biased region until the breakdown voltage for different temperatures. We know 𝑛 concentration would increase with an increase in temperature, and hence minority charges would increase with an increase in temperature. The minority charge carriers are also known as thermally generated carriers, and the reverse current depends on minority carriers only. Hence as the number of minority charge carriers increases, the reverse current would also increase with temperature, as shown in the figure. The reverse saturation current gets doubles with every 10°𝐶 increase in temperature. C-D curve: This curve shows the characteristics of a diode in a reverse biased region from the breakdown voltage point onwards. As with an increase in temperature, loosely bonded electrons are already free, and freeing the other electrons would take more voltage than earlier. Hence breakdown voltage increases with an increase in temperature, as depicted in Fig. 1.18. 1.8. Switching time of a Diode The switching time of a diode is defined as the time it takes to change its state from a forward- biased to a reverse-biased state. In other words, the forward current through the diode doesn't reduce to reverse saturation current as the reverse voltage is applied. Instead, it takes time for the current to reduce from forward to reverse saturation current. This time is also known as reverse recovery time. To discuss the switching time, let's analyze what would happen when we change the diode state from forward bias to reverse bias. This state change takes time which is known as reverse recovery time. First, consider the diode circuit to analyze the diode's switching time, as shown in Fig. 1.19. Fig. 1.19: A diode circuit Initially, when the voltage applied is +V, the diode is in a forward bias state. Hence, there are many minority carriers near the junction. Then, there is an exponential decrease in the concentration of minority carriers and a continuous flow of majority carriers across the junction. Hence, let us assume the current as I in the forward bias. Later, the applied voltage is changed to –V at time t=t1, i.e., the diode is reverse biased. With the instant change in the operation state to reverse bias, the minority carriers start moving in the opposite direction. As a result, the current flow remains the same with a change in direction. However, the high reverse current continues for a shorter duration. As a result, the concentration of the stored minority carriers starts decreasing, and the current also starts decreasing exponentially, as shown in Fig. 1.20. 15  Fig. 1.20: Switching timing of diode The time gap t2 - t1 in which the reverse current is high (i.e., equal to I) is known as storage time, and the time gap from t2 to t3, i.e., the time reverse current becomes equivalent to reverse saturation current, is known as transient time. The total time from t1 to t3 is known as reverse recovery time. Storage time is the time required for majority charge carriers to return to their initial position when the diode is suddenly reverse biased from the forward biased condition". Fig. 1.21 illustrates the concept of the storage time of the diode. Fig. 1.21: Storage timing of diode 1.9. DC Power Supply The DC power supply is a multipurpose circuit used in all electronic devices. The basic principle of a DC power supply is to convert the input AC supply into a DC output voltage. Fig. 1.22 shows the block diagram of a DC power supply. 16  Fig. 1.22: Block diagram of DC power supply It consists of a power transformer, rectifiers, filters, and voltage regulators. The power transformer steps down the application's input to the desired voltage. The Rectifier converts the ac voltage to a pulsating DC voltage. Finally, the regulator maintains a constant output voltage. 2. Diode as a Rectifier The process of converting an AC signal into a DC signal is called rectification. A rectifier is an electronic device that offers low resistance to current in one direction and high resistance to current in the opposite direction. There are two types of rectifiers: (a) Half Wave rectifiers and (b) Full wave rectifiers. 2.1. Half wave Rectifier A halfwave rectifier is a circuit in which the positive or negative half of the AC wave is allowed to pass while the other half is blocked. As a result, the output voltage is low as only half of the input waveform reaches the output. Fig. 1.23 shows a halfwave rectifier circuit and its output waveform. Fig.1.23: Half Wave Rectifier circuit and its output waveform Operation: Equivalent circuit of half wave rectifier for analysis In the positive half cycle of the input voltage, the diode conducts and current 𝑖 flows through 𝑅. 17  𝑖 𝐼 sin 𝛼 ; 0 𝛼 𝜋…………… 1 During the negative half cycle, the diode is reverse biased, and no current flows through the diode or load 𝑅 ∴ 𝑖 0 ; 𝜋 𝛼 2𝜋 … … … … … … … 2 where 𝛼 𝜔𝑡 ∴ Peak Value load Current 𝐼 Where 𝑅 = dynamic resistance of the diode. 𝑅 = Load resistance. (a) DC output current (𝑰𝒅𝒄 ): A DC ammeter indicates the average value of the current passing through it. The average value of a function is given by the area of one cycle of the curve divided by the base. 1 ∴𝐼 𝑖 ∙ 𝑑𝛼 … … … ….. 3 2𝜋 For Half Wave Rectifier 1 𝐼 𝜋 𝐼 𝐼 sin 𝛼 𝑑𝛼 cos 𝛼 ……… 4 2𝜋 2𝜋 0 𝐼 𝐼 𝜋 Limit 0 to  is considered as current flows in this period only. (b) RMS Current ac ammeter (𝑰𝒓𝒎𝒔 ): An AC ammeter indicates the effective or rms current passing through it. It can be calculated as- 1 ∴ 𝐼 𝑖 𝑑𝛼 ………………. 5 2𝜋 𝐼 1 cos 2𝛼 𝑑𝛼 2𝜋 2 𝐼 sin 2𝛼 𝐼 𝛼 𝜋 4𝜋 2 4𝜋 𝐼 𝐼 ………………… 6 2 Note: R.M.S. value of sinusoidal wave is √ (c) DC Voltage: It indicates the average value of the voltage across its terminals. If the voltmeter is connected across a diode and the diode is conducting, it has resistance 𝑅 and the voltage across it is 𝑖𝑅. For a non-conducting diode, the current is zero, and voltage Vi appears across the diode. ∴𝑣 𝑖𝑅 𝐼 𝑅 sin 𝛼 0 𝛼 𝜋 𝑣 𝑉 sin 𝛼 ; 𝜋 𝛼 2𝜋 … … … … … … … … 7 18  ∴ DC Voltmeter reading is given as- 1 𝑉 𝐼 𝑅 sin 𝛼 𝑑𝛼 𝑉 sin 𝛼 𝑑𝛼 2𝜋 1 𝑉 𝐼 𝑅 𝐼 𝑅 𝑅 ∵𝐼 𝜋 𝑅 𝑅 𝐼 𝑅 𝑉 …………. 8 𝜋 𝐼 𝐴𝑠 𝐼 𝜋 ∴ 𝐷𝐶 diode voltage 𝐼 𝑅 (d) Reading of a wattmeter: It indicates the average value of the product of the instantaneous current through its current coil and the instantaneous voltage across its potential coil. 1 ∴ 𝑃 𝑃 𝑉 𝑖 𝑑𝛼 … … … … … … 9 2𝜋 Now 𝑉 𝑖 𝑅 𝑅 for 0 𝛼 𝜋 𝐼 𝑃 𝐼 𝑅 𝑅 𝜋 1 ∴ 𝑃 𝑖 𝑅 𝑅 𝑑𝛼 2𝜋 1 𝐼 sin 𝛼 𝑅 𝑅 𝑑𝛼 2𝜋 𝐼 1 𝐼 𝑅 𝑅 now as 𝐼 sin 𝛼 𝑑𝛼 4 2𝜋 2 𝑃 𝑃 𝐼 𝑅 𝑅 … … … … … … …. 10 (e) Peak Inverse Voltage (PIV): It refers to the maximum voltage a diode can withstand in the reverse-biased direction before breakdown. PIV for H.W.R. = 𝑉 (f) Regulation: It is the percentage change in the output voltage from no-load to full-load. V V % regulation … … … … … 11 V The variation of 𝑉 and 𝐼 for the Half wave rectifier is- 𝐼 𝑉 /𝜋 𝐼 … … … … … ….. 12 𝜋 𝑅 𝑅 𝑉 𝑉 𝐼 𝑅 𝐼 𝑅 … … … … 13 𝜋 𝑉 𝑉 𝜋 19  𝑉 𝐼 𝑅 𝐼 𝑅 𝑅 𝜋 𝑉 ∴𝑉 𝐼 𝑅 𝑉 𝜋 The Thevenin's equivalent circuit for Half Wave Rectifier is as shown below. Fig. 1.24(a): Thevenin's equivalent of Half wave rectifier Fig. 1.24(b): Variation in terminal voltage with load current for ideal & practical power supply (g) Ripple Factor (𝒓): A rectifier should convert AC into DC. However, the output of a halfwave rectifier is not constant (pure DC). Instead, it has periodically fluctuating components remaining in the output wave. The measure of the fluctuating components is given by the ripple factor 'r.' The ripple factor is defined as the ratio of the rms value of the alternating signal component to the average signal value. the rms value of alternating components of a wave r the average value of a wave 𝐼 , 𝑉, … … … … … ….. 14 𝐼 𝑉 Where 𝐼 , and 𝑉 , denotes the 𝑟𝑚𝑠 value of DC components of the current and voltage, respectively. The instantaneous ac components of current 𝑖 𝑖 𝐼 1 ∴ 𝐼 , 𝑖 𝐼 𝑑𝛼 2𝜋 20  1 𝑖 2𝑖𝐼 𝐼 𝑑𝛼 2𝜋 The first term of integral is simply 𝐼 of the total wave. The second term is 1 2𝐼 𝐼 2𝐼 ∵ 𝑖 𝑑𝛼 𝐼 2𝜋 ∴ R.M.S. ripple current 𝐼 , 𝐼 2𝐼 𝐼 𝐼 𝐼 Hence, 𝐼 𝐼 𝐼 𝑟 1 𝐼 𝐼 For half wave rectifier 𝐼 𝐼 /2 1.57 𝐼 𝐼 /𝜋 ∴ 𝑟 1.57 1 1.21 𝑟 121%  𝑟𝑚𝑠 ripple voltage exceeds DC output voltage. ∴ A Halfwave rectifier is a poor circuit for rectification. (h) The ratio of Rectification or Efficiency (𝜼) DC power output 𝑃 𝜂 ac input power 𝑃 𝐼 𝑃 𝐼 𝑅 𝑅 𝜋 𝐼 𝑃 𝐼 𝑅 𝑅 𝑅 𝑅 2 𝐼 𝑅 4 1 ∴ 𝜂 𝜋 ∙ for max 𝜂 , R ∥ R 𝐼 𝜋 𝑅 𝑅 𝑅 1 4 𝑅  Only 40.6% of ac power input is converted into DC power input. (i) Transformer utilization Factor (TUF): The ratio of output DC power delivered to the load to the ac rating of transformer secondary. 𝑃 𝑇𝑈𝐹 𝑎. 𝑐. rating of the transformer secondary Now, AC rating of transformer secondary 𝑉 ∙𝐼 √ 21  𝐼 𝑅 𝑅 𝑅 2√2 Where R resistance of transformer secondary winding 𝐼 ∙𝑅 ∴ 𝑇𝑈𝐹 𝜋 𝐼 𝑅 𝑅 𝑅 2√2 2√2 1 𝑇𝑈𝐹 ∙ 𝜋 𝑅 𝑅 1 𝑅 T.U.F. will be maximum when 𝑅 is very large compared to 𝑅 𝑅 and is given by, 𝑇𝑈𝐹 0.286 Disadvantages of Half wave rectifier (i) Excessive ripple (1.21) (ii) Very low efficiency (0.406) (iii) Less T.U.F. (0.286) (iv) Rectifies only half of the input 2.2. Full Wave Centre tapped rectifier A full-wave rectifier converts the input waveform to one of its output's constant polarity (positive or negative). It converts both polarities of the input waveform to pulsating DC and yields a higher average output voltage. Fig.1.25 shows the centertap full wave rectifier circuit. Fig. 1.25: A Centertap Full Wave Rectifier Circuit A full wave rectifier comprises two halfwave rectifiers. During the positive half cycle of input, the upper transformer secondary winding is positive with respect to the center tap. Hence diode D1 conducts. The lower transformer secondary winding is negative with respect to the center tap; hence, D2 is off(open). During a negative half cycle, reverse action takes place & diode D2 conducts, and D1 is off ( open). Hence upper half of the transformer's secondary winding is disconnected from the load. 22  𝑖𝑑 𝐼 sin 𝜔𝑡 ∴ ; 0 𝜔𝑡 𝜋………… 1 𝑖𝑑 0 and 𝑖𝑑 0 ∴ ; 𝜋 𝜔𝑡 2𝜋 … … … … 2 𝑖𝑑 𝐼 sin 𝜔𝑡 (a) Average value: 1 𝐼 𝐼 𝑖 𝑑𝑡