Lecture 1 - Introduction and Semiconductors.pptx

Electrical Engineering

1. Basic Electronics 1

2. Dr.  Muhammad Jawad Khan Department of Robotics and Artificial Intelligence NUST [email protected] Office: Room 105, RISE Lab Timings: Monday 2~4 PM Class discussion time: Thursday/Friday 1

3. Lab Engineer Engineer Ali Hasan Department of Mechanical Engineering 3

4. Text Books Text: Electronic Devices , 9th Edition, Thomas L. Floyd Ref: Electronic Devices and Circuit Theory, Boylestad and Nashelsky , Ninth Edition Ref: Electronic Devices by Molvino Digital Design. 4th Edition, Morris Mano 8051 Microcontroller, 4th Edition, Scott Mackenzie 4

5. Grading Policy Assignments 5% Quizzes 15% MSE 30% Final 50% Lab work ( 12 ) 67% 33% 100% 5

6. Objectives and Outcomes No. Course Outcomes Book 1. Semiconductor Theory & Electronics Fundamentals Electronic Devices 2. Describe the operation of a diode 3. Diodes and its applications 4. Special Purpose Diodes 5. Bipolar Junction Transistors 6. Construct AND, OR & NOT circuits and truth tables Digital Design 7. Number systems, Boolean algebra, gates 8. Combinational logic (adders, comparators, decoders, multiplexers, etc.) 9. Sequential logic (flip-flops, registers, counters) 10. Microprocessors (registers; ALU; CU; memory, address, data and control buses) 8051 Microcontroller 11. ADC and DAC. Micro-controllers Provide strong foundation for upcoming courses in Mechanical Engineering. 6

7. Course Learning Objectives No CLO PLO Level of learning 1 Design and analyses of electronic circuits using concepts of basic semiconductor electronics PLO3 C4 2 Analyze basic principles of digital logic systems using digit al design techniques. PLO2 C4 3 Demonstrate the basic architecture of Microcontroller by applying it on a problem.   PLO3 C3 7

8. Introduction to Electronics Electronics is the study of flow of signals in electrical circuits. Examples: Entertainment and Communication e.g. TV, Radio Defense Applications e.g. Radar Industrial Applications e.g. power station Medical Services e.g. ECG, X-ray 8

9. Atom Chapter 1 (Floyd) All matter is composed of atoms. An atom is the smallest particle of an element that retains the characteristics of that element There are 118 elements an atom is a single part of an element All atoms consist of electron, proton and neutron. 9

10. Atoms have a planetary of structure that consists of nucleus. Nucleus is the center of an atom The Bohr model of an atom showing Protons (+) Basic particles with positive charge Electrons (-) Basic particles with negative charge Neutrons Uncharged particles 10 The Bohr Model

11. Elements are arranged in periodic table according to their atomic number No. of protons = no. of electrons for a neutral atom, with a net charge on atom as zero Example : Hydrogen has atomic number 1 - 1 proton and 1 electron Helium has atomic number 2 - 2 protons,2 neutrons and 2 electrons 11 Atomic Number

12. Valence Electrons The discrete distance (orbit) from nucleus corresponds to energy level. - Orbits are grouped into energy levels known as shells Maximum number of electron in each shell and n is number of shell Electrons that are in orbits farther from the nucleus have higher energy than those closer to nucleus. - Force of attraction (+ ve charged nucleus & - ve charge electrons) decreases with increasing distance from nucleus Electrons with highest energy at outermost shell is called valence shell and electrons in this shell is called valence electrons.   12

13. Valence Electrons The Bohr model for silicon atom - Silicon atomic number = 14 13

14. Valence Electrons Draw the Bohar model of copper atom Cu. Copper atomic number = 29, atomic mass = 63.54 Draw the Bohar model of germanium atom Ge . Copper atomic number = 32, atomic mass = 72.64 Note: atomic mass , the quantity of  matter  contained in an  atom  of an  element . The observed atomic mass is slightly less than the sum of the masses of the  protons ,  neutrons , and  electrons  that make up the atom. The difference, called the  mass defect , 14

15. Electrons farthest from nucleus have most energy Silicon (Si) vs Copper (Cu) Silicon atomic number = 14 Copper atomic number = 29 Copper is less stable 15

16. Electrons farthest from nucleus have most energy Silicon (Si) vs Germanium ( Ge ) Silicon atomic number = 14 Germanium atomic number = 32 Germanium is less stable. 16

17. Ionization When an atom absorbs energy from heat source or light, energy of electrons are increased Process of loosing valence electron is called Ionization - Escaped valence electron is called free electron - Atom with excess of positive charge is positive ion e.g. Hydogen - Atom with extra electron is called negative ion e.g. Chlorine   17

18. Materials All materials are made up of atoms Conductors – material that conducts electric current – have 1-3 valence electrons e.g. copper (Cu), silver (Ag), gold (Au) Insulators – material that does not conduct electric current – have 5-8 valence electrons e.g. rubber, plastic, glass Semiconductors – material that is between conductors and insulators in its ability to conduct electric current – have 4 valence electrons e.g. silicon (Si), germanium ( Ge ) 18

19. Band Gap The difference in energy between valence band and the conduction band is called band gap Insulator – very high voltage is applied across material Semiconductor – Semiconductors are a special class of elements having a conductivity between that of a good conductor and that of an insulator. ( Boylestad Ch1.2) Conductor – move freely 19

20. Semi conductor materials The three semiconductors used most frequently in the construction of electronic devices are Ge, Si, and GaAs. Single-crystal semiconductors such as germanium (Ge) and silicon (Si) have a repetitive crystal structure, whereas compound semiconductors such as gallium arsenide (GaAs), cadmium sulfide ( CdS ), gallium nitride ( GaN ), and gallium arsenide phosphide ( GaAsP ) are constructed of two or more semiconductor materials of different atomic structures. 20

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22. Covalent bonding and intrinsic materials This bonding of atoms, strengthened by the sharing of electrons, is called covalent bonding. 22

23. The term intrinsic is applied to any semiconductor material that has been carefully refined to reduce the number of impurities to a very low level 23

24. Energy levels The farther an electron is from the nucleus, the higher is the energy state, and any electron that has left its parent atom has a higher energy state than any electron in the atomic structure. Note: valence : the property of an element that determines the number of other atoms with which an atom of the element can combine . 24

25. An electron in the valence band of silicon must absorb more energy than one in the valence band of germanium to become a free carrier. Similarly, an electron in the valence band of gallium arsenide must gain more energy than one in silicon or germanium to enter the conduction band. 25

26. Energy W: Energy Q: Charge of electron V: Potential Difference 26