Electronic Fundamentals PDF - B2 Certification

Module FOR B2 CERTIFICATION 04 ELECTRONIC FUNDAMENTALS Aviation Maintenance Technician Certification Series - Semiconductors - Printed Circuit B...

Module FOR B2 CERTIFICATION 04 ELECTRONIC FUNDAMENTALS Aviation Maintenance Technician Certification Series - Semiconductors - Printed Circuit Boards - Servomechanisms  MODULE 04 FOR B2 CERTIFICATION ELECTRONIC FUNDAMENTALS Aviation Maintenance Technician Certification Series  FORWARD PART-66 and the Acceptable Means of Compliance (AMC) and Guidance Material (GM) of the European Aviation Safety Agency (EASA) Regulation (EC) No. 1321/2014, Appendix 1 to the Implementing Rules establishes the Basic Knowledge Requirements for those seeking an aircraft maintenance license. The information in this Module of the Aviation Maintenance Technical Certification Series published by the Aircraft Technical Book Company meets or exceeds the breadth and depth of knowledge subject matter referenced in Appendix 1 of the Implementing Rules. However, the order of the material presented is at the discretion of the editor in an effort to convey the required knowledge in the most sequential and comprehensible manner. Knowledge levels required for Category A1, B1, B2, and B3 aircraft maintenance licenses remain unchanged from those listed in Appendix 1 Basic Knowledge Requirements. Tables from Appendix 1 Basic Knowledge Requirements are reproduced at the beginning of each module in the series and again at the beginning of each Sub-Module. How numbers are written in this book: This book uses the International Civil Aviation Organization (ICAO) standard of writing numbers. This method displays large numbers by adding a space between each group of 3 digits. This is opposed to the American method which uses commas and the European method which uses periods. For example, the number one million is expressed as so: ICAO Standard 1 000 000 European Standard 1.000.000 American Standard 1,000,000 SI Units: The International System of Units (SI) developed and maintained by the General Conference of Weights and Measures (CGPM) shall be used as the standard system of units of measurement for all aspects of international civil aviation air and ground operations. Prefixes: The prefixes and symbols listed in the table below shall be used to form names and symbols of the decimal multiples and submultiples of International System of Units (SI) units. MULTIPLICATION FACTOR PReFIx SyMbOL 1 000 000 000 000 000 000 = 101⁸ exa E 1 000 000 000 000 000 = 101⁵ peta P 1 000 000 000 000 = 1012 tera T 1 000 000 000 = 10⁹ giga G 1 000 000 = 10⁶ mega M 1 000 = 103 kilo k 100 = 102 hecto h 10 = 101 deca da 0.1 =10-1 deci d 0.01 = 10-2 centi c 0.001 = 10-3 milli m 0.000 001 = 10-⁶ micro µ 0.000 000 001 = 10-⁹ nano n 0.000 000 000 001 = 10-12 pico p 0.000 000 000 000 001 = 10-1⁵ femto f 0.000 000 000 000 000 001 = 10-1⁸ atto a International System of Units (SI) Prefixes iv Module 04 - Electronic Fundamentals  EASA LICENSE CATEGORY CHART A1 B1.1 B1.2 B1.3 B2 Module Number and Title Airplane Airplane Airplane Helicopter Avionics Turbine Turbine Piston Turbine 1 Mathematics X X X X X 2 Physics X X X X X 3 Electrical Fundamentals X X X X X 4 Electronic Fundamentals X X X X 5 Digital Techniques / Electronic Instrument Systems X X X X X 6 Materials and Hardware X X X X X 7A Maintenance Practices X X X X X 8 Basic Aerodynamics X X X X X 9A Human Factors X X X X X 10 Aviation Legislation X X X X X 11A Turbine Aeroplane Aerodynamics, Structures and Systems X X 11B Piston Aeroplane Aerodynamics, Structures and Systems X 12 Helicopter Aerodynamics, Structures and Systems X 13 Aircraft Aerodynamics, Structures and Systems X 14 Propulsion X 15 Gas Turbine Engine X X X 16 Piston Engine X 17A Propeller X X X MODULE 04 SYLLABUS AS OUTLINED IN PART-66, APPENDIX 1. LEVELS CERTIFICATION CATEGORY ¦ B2 Sub-Module 01 - Semiconductors 4.1.1 - Diodes (a) Diode symbols; 2 Diode characteristics and properties; Diodes in series and parallel; Main characteristics and use of silicon controlled rectifiers (thyristors), light emitting diode, photo conductive diode, varistor, rectifier diodes; Functional testing of diodes. (b) Materials, electron configuration, electrical properties; 2 P and N type materials: effects of impurities on conduction, majority and minority characters; PN junction in a semiconductor, development of a potential across a PN junction in unbiased, forward biased and reverse biased conditions; Diode parameters: peak inverse voltage, maximum forward current, temperature, frequency, leakage current, power dissipation; Operation and function of diodes in the following circuits: clippers, clampers, Module 04 - Electronic Fundamentals v  LEVELS CERTIFICATION CATEGORY ¦ B2 full and half wave rectifiers, bridge rectifiers, voltage doublers and triplers; Detailed operation and characteristics of the following devices: silicon controlled rectifier (thyristor), light emitting diode, Schottky diode, photo conductive diode, varactor diode, varistor, rectifier diodes, Zener diode. 4.1.2 - Transistors (a) Transistor symbols; 2 Component description and orientation; Transistor characteristics and properties. (b) Construction and operation of PNP and NPN transistors; 2 Base, collector and emitter configurations; Testing of transistors; Basic appreciation of other transistor types and their uses; Application of transistors: classes of amplifier (A, B, C); Simple circuits including: bias, decoupling, feedback and stabilization; Multistage circuit principles: cascades, push-pull, oscillators, multivibrators, flip-flop circuits. 4.1.3 - Integrated Circuits (a) Description and operation of logic circuits and linear circuits/operational amplifiers; - (b) Description and operation of logic circuits and linear circuits; 2 Introduction to operation and function of an operational amplifier used as: integrator, differentiator, voltage follower, comparator; Operation and amplifier stages connecting methods: resistive capacitive, inductive (transformer), inductive resistive (IR), direct; Advantages and disadvantages of positive and negative feedback. 4.2 - Printed Circuit Boards Description and use of printed circuit boards. 2 4.3 - Servomechanisms (a) Understanding of the following terms: Open and closed loop systems, feedback, - follow up, analogue transducers; Principles of operation and use of the following synchro system components/features: resolvers, differential, control and torque, transformers, inductance and capacitance transmitters. (b) Understanding of the following terms: Open and closed loop, follow up, servomechanism, 2 analogue, transducer, null, damping, feedback, deadband; Construction operation and use of the following synchro system components: resolvers, differential, control and torque, E and I transformers, inductance transmitters, capacitance transmitters, synchronous transmitters; Servomechanism defects, reversal of synchro leads, hunting. vi Module 04 - Electronic Fundamentals  CONTENTS ELECTRONIC FUNDAMENTALS Multi-Layer Semiconductor Devices‥‥‥‥‥‥‥‥‥‥‥‥ 1.32 Welcome‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ iii Shockley Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.32 Revision Log‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ iii Silicon Controlled Rectifiers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.32 Forward‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ iv DIACS And TRIACS‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.34 Contents‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ vii Simple Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.34 Biasing‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.34 SUB-MODULE 01 Configurations ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.36 SEMICONDUCTORS Common-Emitter Configuration ‥‥‥‥‥‥‥‥‥‥ 1.36 Knowledge Requirements‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.1 Common-Collector Configuration ‥‥‥‥‥‥‥‥ 1.36 Semiconductors‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.2 Common-Base Configuration‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.36 Characteristics And Properties ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.2 Basic Amplifier Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.37 Semiconductor Materials‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.3 Class A Amplifiers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.37 Electron Behavior In Valence Shells‥‥‥‥‥‥‥‥‥‥ 1.4 Class AB Amplifiers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.38 Effects of Impurities on P and N Type Materials‥ 1.5 Class B Amplifier ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.38 Majority And Minority Carriers‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.6 Class C Amplifier‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.38 PN Junctions And The Basic Diode‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.7 Cascade Amplifiers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.39 Unbiased PN Junction ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.7 Feedback And Stabilization ‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.39 Forward-Bias PN Junction‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.8 Direct Coupling ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.39 Reverse-Biased PN Junction ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.9 Resistive-Capacitive Coupling‥‥‥‥‥‥‥‥‥‥‥‥ 1.40 Semiconductor Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.9 Impedance Coupling‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.40 Diode parameters‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.9 Transformer Coupling‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.40 Diode Symbols‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.10 Push-Pull Amplifiers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.41 Diode Identification ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.11 Oscillators ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.41 Types Of Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.11 Mutivibrators ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.43 Signal Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.12 Flip-flop Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.43 Photodiodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.13 Integrated Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.43 Light Emitting Diodes ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.13 Binary Numbering System‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.44 Power Rectifier Diodes ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.15 Place Values ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.46 Schottky Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.16 Binary Number System Conversion‥‥‥‥‥‥‥‥‥‥‥ 1.46 Varistor‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.16 Binary-Coded Decimals ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.47 Varactor Diodes‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.17 Logic Gates‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.48 Diode Maintenance And Testing ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.19 NOT Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.48 Diodes In Series And Parallel‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.21 Buffer Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.48 Clipper Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.21 AND Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.49 Clamper Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.22 OR Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.49 Half-Wave Rectifier Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.22 NAND Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.50 Full-Wave Rectifier Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.23 NOR Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.51 Bridge Rectifier Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.23 Exclusive OR Gate‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.51 Voltage Doublers And Triplers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.24 Exclusive NOR Gate ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.51 Transistors‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.25 Negative Logic Gates‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.51 Description, Characteristics, Properties and Symbols‥ 1.25 Aircraft Logic Gate Applications‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.51 Testing of Transistors‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.26 Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.53 Construction And Operation Of Transistors‥‥‥‥‥‥ 1.28 Adder Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.53 Bipolar Junction Transistors‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.28 Flip-Flop Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.53 Unipolar Junction Transistors ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.28 Comparator Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.55 Field Effect Transistors ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.30 Encoder Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.56 Metal Oxide Field Effect Transistors ‥‥‥‥‥‥‥‥‥ 1.31 Decoder Logic Circuits‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.57 Module 04 - Electronic Fundamentals vii  CONTENTS Linear Circuits And Operational Amplifiers‥‥‥‥‥‥ 1.57 SUB-MODULE 03 Positive and Negative Feedback‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.61 SERVOMECHANISMS Voltage Follower Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.61 Knowledge Requirements‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.1 Multivibrator Circuit ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.62 Servomechanisms‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.2 Integrator Circuit ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.62 Feedback: Open-Loop And Closed-Loop Systems‥ 3.2 Differentiator Circuit‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.63 Analog Transducers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.4 Scale Of Integration‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.63 Synchro Systems‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.5 Questions‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.67 DC Selsyn Systems ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.5 Answers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 1.68 AC Synchro Systems‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.6 Torque Synchro Systems‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.8 SUB-MODULE 02 Control Synchro Systems And Synchronous PRINTED CIRCUIT BOARDS Transmitters‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.8 Knowledge Requirements‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.1 Differential Synchro Systems‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.9 Printed Circuit Boards‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.2 Resolver Synchro Systems ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.10 PCB Manufacturing Process‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.2 E-I Inductive Transmitters‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.10 Single-Layer Boards‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.2 Capacitance Transmitters‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.11 Double-Layered Boards‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.2 Stability: Null Hunting, Deadband, And Damping‥ 3.12 Multi-Layer Ed Boards‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.5 Servomechanism Defects‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.13 PCB Repair‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.6 Questions‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.15 Risks And Possible Damage‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.6 Answers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 3.16 Anti-Static Protection‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.8 Controlled Environment ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.8 Acronym Index‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ A.1 Static-Safe Workstation‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.8 Index‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ I.1 Anti-Static Wrist Straps‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.8 Grounding Test Stations‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.9 Ionizers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.9 Special Handling‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.10 Questions‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.11 Answers‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 2.12 viii Module 04 - Electronic Fundamentals  SEMICONDUCTORS PART-66 SYLLABUS LEVELS CERTIFICATION CATEGORY ¦ B2 Sub-Module 01 SEMICONDUCTORS Knowledge Requirements 4.1 - Semiconductors 4.1.1. Diodes (a) Diode symbols; Diode characteristics and properties; Diodes in series and parallel; 2 Main characteristics and use of silicon controlled rectifiers (thyristors), light emitting diode, photo conductive diode, varistor, rectifier diodes; Functional testing of diodes. (b) Materials, electron configuration, electrical properties; 2 P and N type materials: effects of impurities on conduction, majority and minority characters; PN junction in a semiconductor, development of a potential across a PN junction in unbiased, forward biased and reverse biased conditions; Diode parameters: peak inverse voltage, maximum forward current, temperature, frequency, leakage current, power dissipation; Operation and function of diodes in the following circuits: clippers, clampers, full and half wave rectifiers, bridge rectifiers, voltage doublers and triplers; Detailed operation and characteristics of the following devices: silicon controlled rectifier (thyristor), light emitting diode, Schottky diode, photo conductive diode, varactor diode, varistor, rectifier diodes, Zener diode. 4.1.2 Transistors (a) Transistor symbols; 2 Component description and orientation; Transistor characteristics and properties. (b) Construction and operation of PNP and NPN transistors; 2 Base, collector and emitter configurations; Testing of transistors; Basic appreciation of other transistor types and their uses; Application of transistors: classes of amplifier (A, B, C); Simple circuits including: bias, decoupling, feedback and stabilization; Multistage circuit principles: cascades, push-pull, oscillators, multivibrators, flip-flop circuits. Module 04 - Electronic Fundamentals 1.1  PART-66 SYLLABUS LEVELS CERTIFICATION CATEGORY ¦ B2 4.1.3 Integrated Circuits (a) Description and operation of logic circuits and linear circuits/operational amplifiers; - (b) Description and operation of logic circuits and linear circuits; 2 Introduction to operation and function of an operational amplifier used as: integrator, differentiator, voltage follower, comparator; Operation and amplifier stages connecting methods: resistive capacitive, inductive (transformer), inductive resistive (IR), direct; Advantages and disadvantages of positive and negative feedback. Level 2 A general knowledge of the theoretical and practical aspects of the subject and an ability to apply that knowledge. Objectives: (a) The applicant should be able to understand the theoretical fundamentals of the subject. (b) The applicant should be able to give a general description of the subject using, as appropriate, typical examples. (c) The applicant should be able to use mathematical formula in conjunction with physical laws describing the subject. (d) The applicant should be able to read and understand sketches, drawings and schematics describing the subject. (e) The applicant should be able to apply his knowledge in a practical manner using detailed procedures. SEMICONDUCTORS Semiconductors are the building blocks of modern electronics. These devices are electronic components, much like resistors, capacitors, transformers and relays, except that they exploit the electron behavior of semiconductor materials. Since the late 1950's, semiconductor devices have replaced thermionic devices (i.e., vacuum tubes) in most applications. They use electronic conduction in the "solid state", as opposed to the gaseous state such as occurs during thermionic emission in a high vacuum. As such, semiconductors are often referred to as solid-state devices. (Figure 1-1) CHARACTERISTICS AND PROPERTIES Figure 1-1. Solid-state semiconductor devices. The key characteristics that have allowed solid-state devices to replace vacuum tubes in most applications are their small size and weight, low operating voltages, lower well as vacuum tubes for high-power, high-frequency power dissipation, higher reliability and extremely long operation, such as television broadcasting, and they life. In addition, there is no warm up-period required are much more vulnerable to Electro-Static Discharge since semiconductors are absent a cathode heater. (ESD) during handling and operation. However, semiconductors typically do not perform as 1.2 Module 04 - Electronic Fundamentals ESD is the transfer of electrostatic charges between bodies The key to the function of solid-state devices is in the at different potentials caused by direct contact or induced electrical behavior of semiconductors. To understand SEMICONDUCTORS by an electrostatic field. If a solid-state component that semiconductors, the following sections will review what is charged is then suddenly grounded, the charge will makes a material an insulator or a conductor, followed by dissipate to ground, but in the process, the component an explanation for how materials of limited conductivity will be damaged due to excessive heat from breakdown of are constructed and some of their many uses. the dielectric material within the component. Care must be taken to discharge any static electricity from the person SEMICONDUCTOR MATERIALS handling the component and the workstation before The periodic table, shown in Figure 1-2, is a tabular touching sensitive semiconductor devices. arrangement of the chemical elements, organized on the basis of their atomic number (number of protons S em iconduc tor mater ia l s , s uc h a s si l icon a nd in the nucleus), electron configurations, and recurring germanium, exhibit unique properties whereby the chemical properties. Elements are presented in order of conductivity of these materials can be varied and over increasing atomic number, which is typically listed with wide ranges by subtle changes in temperature, light the chemical symbol in each box. intensity, and impurity content. Semiconductors are manufactured both as single discrete devices, such as Elemental semiconductors, known as metalloids on diodes and transistors, and as fully Integrated Circuits, the periodic table, are made from a group of materials which can consist of millions or billions of discrete having electrical conductivities that lie between metal components manufactured and interconnected on a conductors and non-metal insulators. These group IV single semiconductor substrate or wafer. Their long life, elements, such as Carbon (C), Silicon (Si), Germanium reliability, and resilience in harsh environments make (Ge) etc., are known as elemental or single-element them ideal for use in avionics. semiconductors. Silicon is by far the most widely used material in semiconductor devices. Its combination of low raw material cost, relatively simple processing, and Figure 1-2. Periodic table of elements. Module 04 - Electronic Fundamentals 1.3 a useful temperature range make it ideal for use among many applications. Germanium was widely used early Shell or Orbit Number 1 2 3 4 5 on; however, its thermal sensitivity makes it less useful Maximum Number of Electrons 2 8 18 32 50 than silicon. Germanium is often combined with silicon to make very high-speed Silicon-Germanium (SiGe) Figure 1-3. Maximum number of electrons devices. In addition, Silicon is often combined with in each orbital shell of an atom. Carbon to form Silicon-Carbide (SiC) devices for high- power and high-temperature applications. The outer most orbital shell of any atom's electrons is called the valence shell. The number of electrons in the Compound semiconductors do not appear in nature, valence shell determines the chemical properties of the but are synthesized using two or more elements from material. When the valence shell has the maximum groups II through VI of the periodic table. Compound number of electrons, it is complete and the electrons semiconductors that can be synthesized using elements tend to be bound strongly to the nucleus. Materials with from 3rd and 5th group of the periodic table include this characteristic are chemically stable. It takes a large Ga l l ium-A rsenide (Ga As), Ga l l ium-Phosphide amount of force to move the electrons in this situation (GaP), Gallium-Nitride (GaN), Gallium-Aluminum- from one atom valence shell to that of another. Since Arsenide (GaAlAs), Indium-Phosphorus (InP), and the movement of electrons is called electric current, Indium-Antimony (InSb). The color of light that emits substances with complete valence shells are known as from a Light Emitting Diode depends on which of these good insulators because they resist the flow of electrons compounds are used. (i.e., electricity). Most insulators are compounds of two or more elements that share electrons to fill their Compound semiconductors that are synthesized using valence shells. (Figure 1-4) elements from 2nd and 6th group include Cadmium- Selenium (CdSe), Cadmium-Tel lurium (CdTe), In atoms with an incomplete valence shell, that is, those Cadmium-Mercury-Tellurium (CdHgTe), and Zinc- without the maximum number of electrons in their Sulfer (ZnS). Light detectors, such as photocells, are valence shell, the electrons are bound less strongly to the typically made from InSb or CdSe compounds. Any nucleus. The material is chemically disposed to combine combination of elements, such as zinc, cadmium, with other materials or other identical atoms to fill in boron, aluminum, gallium, indium, carbon, silicon, the unstable valence configuration and bring the number germanium, tin, phosphorous, arsenic, antimony, sulfur, of electrons in the valence shell to maximum. Two or selenium, and tellurium, can be formed in to compound more substances may share the electrons in their valence semiconductors with various properties. shells and form a covalent bond. A covalent bond is the method by which atoms complete their valence shells by ELECTRON BEHAVIOR IN VALENCE SHELLS sharing valence electrons with other atoms. An atom of any material has a characteristic number of electrons orbiting the nucleus of the atom. The Electrons in incomplete valence shells may also move arrangement of the electrons occurs in somewhat freely from valence shell to valence shell of different orderly orbits called rings or shells. The closest shell to atoms or compounds. In this case, these are known as the nucleus can only contain two electrons. If the atom free electrons. As stated, the movement of electrons has more than two electrons, they are found in the next orbital shell away from the nucleus. This second shell can only hold eight electrons. If the atom has more Krypton Argon than ten electrons (2 + 8), they orbit in a third shell Neon farther out from the nucleus. This third shell is filled Felium with eight electrons and then a fourth shell starts to fill He Ne Ar Kr if the element still has more electrons. However, when the fourth shell contains eight electrons, the number of electrons in the third shell begins to increase again until a maximum of 18 is reached. (Figure 1-3) Figure 1-4. Elements with full valence shells are good insulators. 1.4 Module 04 - Electronic Fundamentals is known as electric current or current f low. When electrons move freely from atom to atom or compound SEMICONDUCTORS to compound, the substance is known as a conductor. (Figure 1-5) Al Cu Ag Au Aluminum Not all materials are pure elements, that is, substances Copper Silver made up of one kind of atom. Compounds occur when Gold two or more different types of atoms combine. They Figure 1-5. The valence shells of elements that are create a new substance with different characteristics good conductors have 1 or 3 electrons. than any of the component elements. When compounds form, valence shells and their ma ximum number of electrons remain the rule of physics. The new Valence Electrons compound molecule may either share electrons to fill the valence shell or free electrons may exist to make it a good conductor. Si Si Si Si Silicon is an atomic element that contains four electrons in its valence shell. It tends to combine readily with itself and form a lattice of silicon atoms in which adjacent Si Si Si Si atoms share electrons to fill out the valance shell of each to the maximum of eight electrons. The periodic arrangement of atoms in a crystal is a called a lattice. This unique symmetric alignment of silicon atoms Si Si Si Si results in a crystalline structure. (Figure 1-6) Once bound together, the valence shells of each silicon Si Si Si Si atom are complete. In this state, movement of electrons does not occur easily. There are no free electrons to move to another atom and no space in the valence shells to Figure 1-6. The silicon atoms with just the valence shell electrons share. accept a free electron. Therefore, silicon in this form is somewhat of an insulator. EFFECTS OF IMPURITIES ON P AND N TYPE MATERIALS Since silicon in its ultra-pure form is an insulator, it must be transformed into a semi-conductive material by adding some impurities to the silicon - this process is known as doping. Arsenic (As), phosphorus (P), or some other element with five valence electrons in each atom is mixed into the molten silicon. Selective cooling of the molten material causes solidification to occur across a particular crystal direction. Crystal growth is enhanced by placing a small "seed" crystal at the end which is cooled first. The seed crystal is lowered into the molten material and is raised slowly allowing the crystal to grow onto the seed. The crystal pulled and rotated slowly from the melt as it grows into the shape of an ingot. (Figure 1-7) Figure 1-7. Silicon crystals are grown from molten silicon. Impurities added to the molten mixture determine if the crystal will be P-type or N-type material. Module 04 - Electronic Fundamentals 1.5  Free Electron Si Si Si Si Si Si Si Si Si Si Si Si Si As Si Si As Si Si As Si Si As Si Si Si Si Si Si Si Si Si Si Si Si Si Figure 1-8. Silicon atoms doped with arsenic form a lattice work of covalent bonds. Free electrons exist in the material from the arsenic atom’s 5th valence electron. These are the electrons that flow when the semiconductor material, known as N-type or donor material, is conducting. The result is a silicon lattice with flaws. The elements are only seven electrons and not eight. This greatly bond, but numerous free electrons are present in the changes the properties of the material. The absence of material from the 5th electron that is part of the valence the electrons, called holes, encourages electron flow due shell of the doping element atoms. These free electrons to the preference to have eight electrons in all valence can now flow under certain conditions. Thus, the silicon shells. Therefore, this type of doped silicon is also becomes semi-conductive. semi-conductive. It is known as P-type material or as an acceptor since it accepts electrons in the holes under When silicon is doped with an element or compound certain conditions. (Figure 1-9) containing five electrons in its valence shell, the result is a negatively charged material due to the excess free MAJORITY AND MINORITY CARRIERS electrons, and the fact that electrons are negatively Both N-type and P-type semiconductors are able to charged. This is known as an N-type semiconductor conduct electricity. In the N-type material, current material. It is also known as a donor material because, f lows primarily like it does in any conductor. The when it is used in electronics, it donates the extra valence electrons move from one valence shell to another electrons to current flow. (Figure 1-8) as they progress through the material. Due to the surplus of electrons, the electrons are considered the Doping silicon can also be performed with an element majority current carriers in N-type semiconductors. Any that has only three valence electrons, such as boron, movement of current in N-type material by the filling of gallium, or indium. Valence electron sharing still occurs, holes is considered the minority current carrier. and the silicon atoms with interspersed doping element atoms form a lattice molecular structure. However, in this case, there are many valence shells where there A “hole” exists because there is no electron in the boron to form covalent bond here. Si Si Si Si Si Si Si Si Si Si Si Si Si B Si Si B Si Si B Si Si B Si Si Si Si Si Si Si Si Si Si Si Si Si Figure 1-9. The lattice of boron doped silicon contains holes where the three boron valence shell electrons fail to fill in the combined valence shells to the maximum of eight electrons. This is known as P-type semiconductor material or acceptor material. 1.6 Module 04 - Electronic Fundamentals In P-type material, current primarily flows by valence PN JUNCTIONS AND THE BASIC electrons filling holes that exist in the doped lattice. DIODE SEMICONDUCTORS This makes holes the majority carrier in P-type material. A single type of semiconductor material by itself is Any current flow in P-type material that occurs without not very useful. But, applications have been developed holes (valence electrons exchanging with other valence when P-type and N-type materials are joined that have electrons) is known as the minority carrier. revolutionized electrical and electronic devices. The boundary where the P-type material touches the N-type Figure 1-10 shows the progression of a hole moving material is called the PN junction. Interesting and useful through a number of atoms. Notice that the hole phenomenon occur at this contact region. Furthermore, illustrated at the far left of the top depiction of the figure when joined, the entire two-element semiconductor attracts the next valance electron into the vacancy, which device becomes a basic diode. then produces another vacancy called a hole in the next position to the right. Once again, this vacancy attracts A diode is an electrical device that allows current to flow the next valance electron. This exchange of holes and in one direction through the device but not the other. electrons continues to progress, and can be viewed in Because of this, the semiconductor diode is used in one of two ways: electron movement or hole movement. electronic circuits to convert Alternating Current (AC) into Direct Current (DC). Thus, the PN semiconductor For electron movement, illustrated by the top depiction device can act as a rectifier. An explanation of what of Figure 1-10, the electron is shown as moving from happens at the PN junction and how it affects the entire the right to the left through a series of holes. In the PN semiconductor device follows. A glass encased second depiction in the f igure, the motion of the semiconductor diode is shown in Figure 1-11. vacated hole can be seen as migration from the left to the right, called hole movement. The valence electron UNBIASED PN JUNCTION in the structure will progress along a path detailed by Figure 1-12 illustrates the electrical characteristics the arrows. Holes, however, move along a path opposite of an unbiased diode, which means that no external that of the electrons. voltage is applied. The P-side in the illustration is shown to have many holes, while the N-side shows Combining N-type and P-type semiconductor material many electrons. When the P and N material contact in certain ways can produce very useful results. The each other, the electrons on the N-side tend to diffuse following section will discuss what occurs at the out in all directions. Some of the electrons enter the junction of the N-type and P-type material when a P region. With so many holes in the P material, the voltage is applied. electrons soon drop into a hole. When this occurs, the hole then disappears. A negatively charged ion is created since there is now one more electron than the number of protons in the nucleus of the boron (or gallium or Electron Movement indium) atom to which the hole belonged. Hole Movement Silicon atom showing one of the electrons in its valence shell. Silicon atom in which one electron has broken out of its valence shell and left a hole. Electron moving from one silicon atom to another and leaving a hole. Figure 1-11. A silicon diode, the square crystal Figure 1-10. A hole moving through atoms. silicon can be seen between the two leads. Module 04 - Electronic Fundamentals 1.7  P-Type N-Type Meanwhile, in the N material near the junction, the valence electrons that departed for the P-type material leave behind a band of positive ions since there are now more positively charged protons in the nucleus of the arsenic (or phosphorous, etc.) atoms than there are electrons in their shells. Thus, each time an electron crosses the PN junction, it creates a pair of ions. In Depletion Zone Figure 1-12, this is shown in the area outlined by the Holes Electrons dash lines. The circled plus signs and the circled negative P-Type N-Type signs are the positive and negative ions, respectively. These ions are fixed in the crystal and do not move around like electrons or holes in the conduction band. They constitute the depletion zone where neither excess electrons nor excess holes exist. The ions create an electrostatic field across the junction between the Negative Ions Positive Ions oppositely charged ions. Because holes and electrons must overcome this field Represents Electrostatic Field (Potential Hill) to cross the junction, the electrostatic field is usually called a barrier or potential hill. As the diffusion of Figure 1-12. An unbiased PN junction – the depletion zone creates electrons and holes crosses the junction, the strength of a barrier that electrons or holes must overcome for current to flow. the electrostatic field increases until it becomes strong The electrostatic field that forms that barrier is shown by a battery enough to prevent more electrons or holes from crossing circuit involving the positive and negative ions in the depletion zone. over. At this point, a state of equilibrium exists and there is no further movement across the junction. The PN junction and the entire PN device is said to be unbiased. Narrow Depletion Zone FORWARD-BIAS PN JUNCTION P-Type N-Type The two semiconductors joined at the PN junction form a diode that can be used in an electrical circuit. When a voltage source (e.g., battery) is attached to the diode with the negative terminal connected to the N-type semiconductor material and the positive Decreased Potential Hill terminal connected to the P-type material, it is said to have forward bias and electricity can flow in the circuit. Electron Flow (Figure 1-13) + - The voltage opposes the electrostatic field at the junction Figure 1-13. The flow of current and the PN junction of a forward and reduces the potential hill. The positive potential of biased semiconductor diode in a simple circuit with battery. the battery forces holes in the P-type material toward the junction. The negative potential of the battery current flow. When disconnected from the battery, the forces free electrons in the N-type material towards depletion zone widens, the electrostatic field strength is the opposite side of the junction. The depletion zone restored and current flow ceases. becomes very narrow and electrons in the N-type material f low across into the P-type material. There, Note that the potential hill or barrier is reduced when they combine with holes. The electron and holes connected to the battery as explained but it still exists. continuously come together resulting in current flow. A voltage of approximately 0.7 volts is needed to begin These majority carriers in each semiconductor material the current f low over the potential hill in a silicon increase in number as voltage is increased. This increases semiconductor diode and about 0.3 volts in a germanium 1.8 Module 04 - Electronic Fundamentals semiconductor diode. Thereafter, current flow is linear with the voltage. Caution must be exercised because it SEMICONDUCTORS Widened Depletion Zone is possible to overheat and "burn out" the semiconductor P-Type N-Type device at the junction with excessive current flow. Also note that temperature has a significant impact of current flow in semiconductors. REVERSE-BIASED PN JUNCTION When the battery connections to the PN semiconductor Increased Potential Hill are reversed, as shown in Figure 1-14, the diode is said to have reverse bias and current will not flow. The most noticeable effect of reverse bias seen in this illustration is - + the widened depletion zone. Figure 1-14. Reversed biased PN junction has no current flow. SEMICONDUCTOR DIODES Semiconductor diodes are used often in electronic A brief description including the type of diode, the circuits. As discussed in the previous section, PN major area of application, and any special features is junction diodes offer very little resistance to electrical normally given in the specification sheets. Of particular current when forward biased and maximum resistance interest is the specific application for which the diode when the diode is reverse biased. When AC current is suited. The manufacturer will also provide a drawing is applied to a diode, current f lows during one cycle of the diode, which gives its dimension, weight, and, if of the sine wave but not during the other cycle. The appropriate, any identification marks. A static operating diode, therefore, becomes a rectif ier and changes table giving spot values of parameters under f ixed the AC current to a pulsating DC current. When conditions is often given and sometimes a characteristic the semiconductor diode is forward biased, electrons curve, similar to the one shown in Figure 1-15, is flow; when the AC cycles, the diode becomes reverse also supplied. The right side of the graph shows the biased and electrons do not flow. This sub-module will current characteristics of a diode when it is forward go into further detail on diode parameters, symbols, biased and the left side of the graph shows the current identif ication and behavior. It will also detail the characteristics of a reverse biased diode. operation of various types of diodes, and show how they are used in power supplies and other common circuits. DIODE PARAMETERS Semiconductor diodes have properties that enable them to Burn-Out perform many different electronic functions. To do their Current jobs, engineers and technicians must be supplied with data on these different types of diodes. The information Forward Current (MA) presented for this purpose is called parameters. These parameters are supplied by manufacturers either in their Avalanche Voltage manuals or on specification sheets, also called data sheets. Voltage Because of the scores of manufacturers and numerous diode types, it is not practical to present a specification 0.7 Volts sheet here and call it typical. Aside from the difference Leakage Reverse Current ( A) between manufacturers, a single manufacturer may Current supply specification sheets that differ both in format and content. Despite these differences, certain performance Reverse Bias Forward Bias and design information is required as follows. Figure 1-15. Silicon PN junction diode characteristics. Module 04 - Electronic Fundamentals 1.9 Finally, the specification sheets provide the diode ratings 6. Reverse Recovery Time (Trr) - the time it takes since they are the limiting values of operating conditions for a diode to "turn off "after it switches from outside of which the diode could be damaged. PN being forward-biased to reverse-biased. For junction diodes are generally rated for the following: rectifier diodes, recovery time may be in tens of 1. Maximum (Average) Forward Current (IFAV) – microseconds; whereas signal diodes typically this is the maximum average amount of current recover in only a few nanoseconds. that the diode is able to conduct in forward bias, 7. Total Power Dissipation - the maximum amount which is directly proportional to the amount of power that the diode can dissipate in the form of voltage applied. However, there is a thermal of heat when it is forward biased (conducting) limitation regarding how much heat the PN due to some internal resistance. To find the power junction can withstand before a structural dissipation, multiply the voltage drop across the breakdown can occur. Maximum average forward diode time the current flowing through it. This current is usually given at the maximum power rating, measured in watts, is limited by the diode's dissipation at a specific temperature, typically at thermal capacity. 25 ˚C. A resistor may be used in series with the 8. Maximum Operating Temperature – the maximum diode to limit the forward current. allowable junction temperature before the structure 2. Maximum (Peak or Surge) Forward Current of the diode deteriorates. It is expressed in units of (IFSM) - the maximum peak or surge amount of degrees centigrade per watt. current that the diode is able to conduct in forward bias in the form of either recurring pulses (peak) All of the above ratings are subject to change with or nonrecurring pulses (surge). Again, this rating temperature variations. If, for example, the operating is limited by the diode's PN junction's thermal temperature is above that stated for the ratings, the capacity, and is usually much higher than the ratings must be decreased, or heat sinks may need average current rating due to the time it takes to to be attached to the diode to maintain its operation reach maximum junction temperature for a given below the rated junction temperature. Since many of current. Current should not equal this value for these parameters vary with temperature, or some other more than a few milliseconds. operating condition, manufacturers typically provide 3. Maximum Forward Voltage Drop at Indicated graphs that show the component ratings plotted against Forward Current (VF@IF) - the maximum other variables, such as temperature, so that the engineer forward voltage drop across the diode at the and technician have a better idea of the capabilities of indicated forward current. the particular device being used. 4. Maximum Reverse Current (IR) - the very small value of direct current that flows when a DIODE SYMBOLS semiconductor diode is in reverse bias mode and Diode symbols used in circuit diagrams are shown in is below the peak inverse voltage applied. This Figure 1-16. Different types of diodes have slightly is known as leakage current and is in the micro altered symbols for identification. These will be shown amperage range. as they are discussed. 5. Maximum Reverse Voltage (VR) – also known as the Peak Inverse Voltage (PIV), is the maximum amount of voltage that the diode can withstand continually in the reverse-bias mode without causing a PN junction breakdown. As mentioned, a small amount of current flows through a semiconductor diode when it is reversed biased. However, at a certain voltage, the blockage of current flow in a P N reversed biased diode breaks down completely. This is known as the avalanche voltage or zener voltage. It is the voltage at which a normal diode can no longer Anode Cathode hold back the reverse current, and as a result, it fails. Figure 1-16. Semiconductor diode symbols. 1.10 Module 04 - Electronic Fundamentals Note that electron flow is typically discussed in this device and is a number one less than the number of text. The conventional current f low concept where active elements. Thus 1 designates a diode; 2 designates SEMICONDUCTORS electricity is thought to flow from the positive terminal a transistor (which may be considered as made up of of the battery through a circuit to the negative terminal two diodes); and 3 designates a tetrode (a four-element is sometimes used in the field. To differential between transistor). The letter "N" following the first number the two flows in diagrams, the arrows in Figure 1-17 indicates a semiconductor. The 2- or 3-digit number may be used. following the letter "N" is a serialized identification number. If needed, this number may contain a suffix DIODE IDENTIFICATION letter after the last digit. For example, the suffix letter There are many types of diodes varying in size from "M" may be used to describe matching pairs of separate the size of a pinhead (used in subminiature circuitry) to semiconductor devices, or the letter "R" may be used large 250-ampere diodes (used in high-power circuits). to indicate reverse polarity. Other letters are used to Because there are so many different types of diodes, indicate modified versions of the device which can be some system of identification is needed to distinguish substituted for the basic numbered unit. one diode from another. This is accomplished with the semiconductor identification system shown in Figure For example, a semiconductor diode designated as 1-18. This system is not only used for diodes, but for type 1N345A signif ies a two-element diode (1) of transistors and many other special semiconductor semiconductor material (N) that is an improved version devices as well. (A) of type 345. As illustrated in this Figure 1-18, the system uses When working with these different types of diodes, numbers and letters to identify different types of it is also necessary to distinguish one end of the diode semiconductor devices. The first number in the system from the other (anode from cathode). For this reason, indicates the number of junctions in the semiconductor manufacturers generally code the cathode end of the diode with a "k," "+," "cath," a color dot or band, or by an unusual shape (raised edge or taper) as shown in Figure 1-19. In some cases, standard color code bands are Electron Flow placed on the cathode end of the diode. This serves two purposes: (1) it identifies the cathode end of the diode, and (2) it also serves to identify the diode by number. Conventional Current Flow Figure 1-17. Current flow arrows used on diagrams. The standard diode color code system is shown in Figure 1-20. Take, for example, a diode with brown, orange, and white bands at one terminal and figure out its XNYYY identification number. With brown being a "1," orange XN YYY a "3," and white "9," the device would be identified as a type 139 semiconductor diode, or specifically 1N139. Component Identification Number TYPES OF DIODES This section will provide a detailed discussion of the X- Number of Semiconductor Junctions operation and characteristics of many common diodes N - A Semiconductor YYY - Identification Number (Order or Registration Number) in use today, including the zener diode, silicon diode, also includes suffix letter (if applicable) to indicate: photo-conductive diode, light-emitting diode, power 1. Matching Devices rectifier diode, Schottky diode, varistor and varactor 2. Reverse Polarity diode. A discussion of silicon controller rectif iers 3. Modification (thyristor) will take place in submodule 1.2 since it more Example - 1N345A closely resembles a transistor. (An improved version of the semiconductor diode type 345) Figure 1-18. Semiconductor Identification Codes. Module 04 - Electronic Fundamentals 1.11  2 Digit Type (Black Band) 3 Digit Type Band Suffix Letter Marked (If Used) 2 4 Digit Type Marked Suffix Letter 2 (Black if No Letter) Color Spot Anodes Cathodes 1st 2nd 3rd 4th Glass Digits 1 1 2 Color Digit Diode Suffix Letter Black 0 - Brown 1 A Color Bands Red 2 B Orange 3 C Yellow 4 D Glass Green 5 E Blue 6 F Violet 7 G Gray 8 H White 9 J Silver - - Marked Gold - - None - - Figure 1-20. Semiconductor diode color code system. Figure 1-19. Semiconductor Diode Markings. SIGNAL DIODES A signal diode is a small non-linear semiconductor Diodes can be designed with a zener voltage. This is t y pically found in electronic circuits where high similar to avalanche flow. When reversed biased, only frequencies or small currents are involved, such as leakage current flows through the diode. However, as television and radio signal processing, and digital logic the voltage is increased, the zener voltage is reached. The circuits. The PN junction is usually encapsulated in diode lets current flow freely through the diode in the glass and it has a black or red band at the cathode end. direction in which it is normally blocked. The diode is (Figure 1-22) constructed to be able to handle the zener voltage and the resulting current, whereas avalanche voltage burns out Signal diodes have lower current (i.e., 150mA) and an ordinary diode. A zener diode can be used as means power ratings (i.e., 500mw) than rectifier diodes, but of dropping or regulating voltage. It can be used to step function better in high frequency applications or in down circuit voltage for a particular application, but only clipping or switching circuits that deal with short when certain input conditions exist and are constructed duration pulse waveforms. Signal diodes can be made of to handle a wide range of voltages. (Figure 1-21) either silicon or germanium diodes. Germanium signal 1.12 Module 04 - Electronic Fundamentals  The extra energy frees an electron enabling it to flow as current. The vacated position of the electron becomes a SEMICONDUCTORS Current Flow hole. In light-sensitive diodes, often called photodiodes or photocells, this occurs in the depletion area of the reversed biased PN junction turning "on" the device and (+) Anode Cathode (-) allowing current to flow. - + Figure 1-23 illustrates a photodiode in a coil circuit. In IZ this case, the light striking the photodiode causes current RS to f low in the circuit whereas the diode would have VA otherwise blocked it. The result is the coil energizes and closes another circuit enabling its operation. Thermal D1 V2 RL energy produces minority carriers in a diode. As the temperature rises, so does the current. Light energy can also produce minority carriers. By using a small window Figure 1-21. A Zener diode, when reversed biased, will to expose the PN junction, a photodiode can be built. breakdown and allow a prescribed voltage (V₂) to flow When light fall upon the junction of a reverse-biased in the direction normally blocked by the diode. photodiode, electrons-hole pairs are created inside the depletion layer. The stronger the light, the greater the number of light-produced carriers, which in turn, causes a greater magnitude of reverse-current. Because of this characteristic, the photodiode can be used in light detecting circuits, such as proximity detectors and fiber optic data bus receivers. LIGHT EMITTING DIODES Light Emit ting diodes (LEDs) have become so commonly used in electronics that their importance may tend to be overlooked. Numerous avionics displays and indicators use LEDs for indicator lights, digital Figure 1-22. 1N914 signal diode used as a readouts, and backlighting of liquid crystal display radio frequency signal detector. (LCD) screens. diodes have a lower forward voltage drop (0.3v) across the PN junction than silicon signal diodes (0.7v), but have a higher forward resistance. Silicon diodes have higher forward current and higher reverse voltage peak values. The most common sizes for signal diodes are Photodiode Symbol those rated with a maximum reverse voltage of 100v, 120v, 150v and 200v. PHOTODIODES Simple Coil Circuit Light contains electromagnetic energy that is carried by photons. The amount of energy depends on the frequency of light of the photon. This energy can be + very useful in the operation of electronic devices since all semiconductors are affected by light energy. When a − photon strikes a semiconductor atom, it raises the energy level above what is needed to hold its electrons in orbit. Figure 1-23. Illustrates a photodiode in a coil circuit. Module 04 - Electronic Fundamentals 1.13 LEDs are simple and reliable. They are constructed When the diode is forward biased, the energy given off of semiconductor material. In a forward biased diode, is visible in the color characteristic for the material being electrons cross the junction and fall into holes. As the used. Figure 1-25 illustrates the anatomy of a single electrons fall into the valence band, they radiate energy. LED, the symbol of an LED, and a graphic depiction of This is true in all semiconductor materials. In most the LED process. diodes, this energy is dissipated as heat. However, in the light-emitting diode, the energy is dissipated as LEDs are used widely as "power on" indicators of current light. By using elements, such as gallium, arsenic, and and as displays for pocket calculators, digital voltmeters, phosphorous, an LED can be designed to radiate colors, frequency counters, etc. For use in calculators and such as red, green, yellow, blue and infrared light. LEDs similar devices, LEDs are typically placed together in that are designed for the visible light portion of the seven-segment displays, as shown in Figure 1-26 (view spectrum are useful for instruments, indicators, and A and view B). This display uses seven LED segments, even cabin lighting. The advantages of the LED over or bars (labeled A through G in the figure), which can the incandescent lamps are longer life, lower voltage, be lit in different combinations to form any number faster on and off operations, and less heat. Figure 1-24 from "0" through "9." The schematic, view A, shows is a table that illustrates common LED colors and the a common-anode display. All anodes in a display are semiconductor material that is used in the construction internally connected. of the diode. Color Wavelength (nm) Voltage (V) Semiconductor Material Infrared 760 ∆V < 1.9 Gallium arsenide (GaAs) Aluminium gallium arsenide (AlGaAs) Red 610 760 1.63 < ∆V < 2.03 Aluminium gallium arsenide (AlGaAs) Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP) Orange 590 610 2.03 < ∆V < 2.10 Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP) Yellow 570 590 2.10 < ∆V < 2.18 Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP) Green 500 570 1.9 < ∆V < 4.0 Indium gallium nitride (InGaN) / Gallium(III) nitride (GaN) Gallium(III) phosphide (GaP) Aluminium gallium indium phosphide (AlGaInP) Aluminium gallium phosphide (AlGaP) Blue 450 500 2.48 < ∆V < 3.7 Zinc selenide (ZnSe) Indium gallium nitride (InGaN) Silicon carbide (SiC) as substrate Silicon (Si) as substrate — (under development) Violet 400 450 2.76 < ∆V < 4.0 Indium gallium nitride (InGaN) Purple Multiple Types 2.48 < ∆V < 3.7 Dual blue/red LEDs, blue with red phosphor, or white with purple plastic Ultraviolet 400 3.1 < ∆V < 4.4 diamond (235 nm) Boron nitride (215 nm) Aluminium nitride (AlN) (210 nm) Aluminium gallium nitride (AlGaN) Aluminium gallium indium nitride (AlGaInN) — (down to 210 nm) White Broad Spectrum ∆V = 3.5 Blue/UV diode with yellow phosphor Figure 1-24. Table that illustrates common LED colors and the semiconductor material that is used in the construction of the diode. 1.14 Module 04 - Electronic Fundamentals  + − Expoxy Lens/Case SEMICONDUCTORS Wire Bond P-Type N-Type Reflective Cavity Semiconductor Die Anvil Post Leadframe Hole Electron Flat Spot Conduction Band Light Band Gap Anode Cathode Recombination Valence Band Figure 1-25. Table that illustrates common LED colors and the semiconductor material that is used in the construction of the diode. A A A A F B F B F B F B G G G G E C E C E C E C D D D D (A) (B) (A) (B) Figure 1-26. Seven-segment LED display. Figure 1-27. Seven-segment LED display examples. When a negative voltage is applied to the proper cathodes, a number is formed. For example, if negative voltage is applied to all cathodes except that of LED "E," the number "9" is produced, as shown in view A of Figure 1-27. If the negative voltage is changed and applied to all cathodes except LED "B," the number "9" changes to "6", as shown in view B. Figure 1-28. Stacked seven-segment LED display. Seven-segment displays are also available in common- cathode form, in which all cathodes are at the same POWER RECTIFIER DIODES potential. When replacing LED displays, one must The rectifier diode is usually used in applications that ensure the replacement display is the same type as the require high current, such as power supplies. The faulty display. Since both types look alike, one should range in which the diode can handle current can vary always check the manufacturer's number. LED seven- anywhere from one ampere to hundreds of amperes. segment displays range from the very small, often not One common example of a series of power rectifier much larger than standard typewritten numbers, to diodes are those with part numbers 1N4001 to 1N4007. about an inch. Several displays may be combined in a The "1N" indicates that there is only one PN junction, or package to show a series of numbers, such as the one that the device is a diode. The average current carrying shown in Figure 1-28. range for these rectifier diodes is one ampere and they Module 04 - Electronic Fundamentals 1.15 have a peak inverse voltage between 50 volts to 1 000 Figure 1-30 illustrates a Schottky diode with its volts. Larger rectifier diodes can carry currents up to 300 schematic symbol. amperes when forward biased and have a peak inverse voltage of 600 volts. A recognizable feature of the larger rectifier diodes is that they are encased in metal in order N-Type to provide a heat sink. Figure 1-29 illustrates a few types Metal Material of rectifier diodes. SCHOTTKY DIODES A Schottky diode is designed to have metal, such as gold, silver, or platinum, on one side of the junction and doped silicon, usually an N-type, on the other side of the Figure 1-30. Schottky diode construction and schematic symbol. junction. In this respect, it is not a pure semiconductor diode. It is a metal-semiconductor diode. A Schottky diode is considered a unipolar device because free VARISTOR electrons are the majority carrier on both sides of the A varistor is not exactly a semiconductor diode. It is junction. The Schottky diode has no depletion zone or typically made of a ceramic mass of zinc oxide grains charge storage, which means that the switching time can in a matrix of other metal oxides. This material is be as high as 300 MHz. The typical PN semiconductor sandwiched between two metal plates which are the switches much slower. When an opposite voltage to the electrodes. (Figure 1-31) The numerous grains form voltage supply that forward biases a PN junction diode is diode relationships with other grains so that current applied, current in the diode continues to flow for a brief f lows in one direction only through the device. The moment. This time is measurable and is known as reverse current - voltage relationship is non-linear. A small recovery time. Schottky diode reverse recovery time or moderate amount of voltage applied to the varistor is much shorter, which makes it suited for use in high causes very little current flow. However, when a large frequency rectification. It also has a very low voltage drop voltage is applied, the effective junction breaks down (0.15 volts versus 0.7 volts for a silicon diode). and large current flow follows. Therefore, the varistor has high resistance at low voltage, and low resistance (+) Anode Cathode (-) Schematic Symbol Approx. 0.75" Approx. 0.75"