Electromagnetism, electricity and digital electronics


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Electromagnetism, electricity and digital electronics

  1. 1. <ul><li>Electromagnetism, Electricity </li></ul><ul><li>And Digital Electronics </li></ul><ul><li>By </li></ul><ul><li>Engr. Jorge P. Bautista </li></ul>
  2. 2. Course Outline <ul><li>Theory of Electrons and Electricity </li></ul><ul><li>Resistor and other passive elements </li></ul><ul><li>Ohm’s Law and Electric Circuits </li></ul><ul><li>Theory of Magnetism </li></ul><ul><li>Diode and other Electronic Devices </li></ul><ul><li>Logic Gates and flip-flops </li></ul><ul><li>Combinational and sequential circuits </li></ul>
  3. 3. Text and References <ul><li>Digital Design by Mano </li></ul><ul><li>Electronic Devices by Floyd </li></ul><ul><li>Engineering Circuit Analysis by Hayt </li></ul><ul><li>Introduction to Electric Circuits by Dorf </li></ul><ul><li>Introduction to Digital Circuits by Bogart </li></ul>
  4. 4. Theory of Electrons <ul><li>Principles of Electrons: </li></ul><ul><li>Electrons orbit the nucleus of an atom at certain distances from the nucleus. Electrons near the nucleus have less energy than those in more distant orbits. </li></ul><ul><li>Bohr’s Atomic Theory of an atom </li></ul><ul><li>An atom consist of a nucleus in which it consist of a neutron and a proton in which electrons orbit around it. </li></ul>
  5. 5. Shells of an Atom <ul><li>In an atom, orbits are group into energy bands know as shells. Each shell has a fixed maximum number of electrons at permissible energy levels. The shells are designated as K,L,M,N, and so on. The outermost shell is know as valence shell and the electrons in this shell are called valence electrons . These valence electrons contribute to chemical reactions and bonding. </li></ul>
  6. 6. Shells of orbital Electrons in an Atom 50 18 14 10 6 2 O 32 14 10 6 2 N 18 10 6 2 M 8 6 2 L 2 2 K Total g f d p s
  7. 7. Parts of an Atom <ul><li>Proton – positively charge particle </li></ul><ul><li>Electron – negatively charge particle </li></ul><ul><li>Neutron – neutral charge particle or no charge at all. </li></ul>
  8. 8. Ionization <ul><li>Ionization – the process of losing a valence electrons. </li></ul><ul><li>Ion – the resulting positively charge atom </li></ul><ul><li>Free electrons – the escaped valence electron. </li></ul><ul><li>Positive ion – ions that loses an electron </li></ul><ul><li>Negative ion – ions that gained an electron </li></ul>
  9. 9. What are insulators, conductors and semi-conductors? <ul><li>Insulator – name given to materials that do not conduct electricity. They have less than 8 free electrons </li></ul><ul><li>Conductor – name given to materials that is a good conductor of electricity. They have many free electrons </li></ul><ul><li>Semiconductor – materials having 8 valence electrons. </li></ul>
  10. 10. Some insulators and conductors <ul><li>*Insulator *Conductor </li></ul><ul><li>Glass Gold </li></ul><ul><li>Porcelain Silver </li></ul><ul><li>Mica Copper </li></ul><ul><li>Rubber Aluminum </li></ul><ul><li>Asbestos Zinc </li></ul><ul><li>Paraffin Tin </li></ul><ul><li>Paper Lead </li></ul><ul><li>Air iron </li></ul>
  11. 11. WIRE SIZES 1.4A 212.872 0.3200 28 3.5A 84.1976 0.5105 24 7A 52.9392 0.6451 22 211A 0.4063 7.3482 1 245A 0.3224 8.2524 0 Ampacity Ohms per Km Diameter, mm AWG gauge
  12. 12. What is Electricity? <ul><li>Electricity is </li></ul><ul><li>the flow of electrons from an area high in electron excess to one of lower electron content. </li></ul><ul><li>the flow of energy in a wire (similar to the flow of water in a pipe) that is invisible, that causes the wire to become hot , causes a magnetic field to develop around the wire and can be put to work driving pumps, blowers, fans and so forth. </li></ul><ul><li>Electricity cannot be generated. It can neither be created nor destroyed. It can, however, be forced to move and thus transmit power or produce electrical phenomena. </li></ul><ul><li>Two types of electricity: </li></ul><ul><li>Static electricity – electricity at rest </li></ul><ul><li>Dynamic electricity – electricity in motion </li></ul>
  13. 13. Common Sources of Electrical energy or Power. <ul><li>1. Battery – a single unit capable of producing DC voltage by converting chemical energy into electrical energy. </li></ul><ul><li>2. Dynamo – a machine that converts mechanical energy to electrical energy and vice versa. </li></ul><ul><li>3. Motor – transformation from electrical energy to mechanical energy. </li></ul><ul><li>4. Generator – transformation from mechanical energy to electrical energy. </li></ul><ul><li>5. Solar energy – it converts solar energy from the sun through the use of solar cells. </li></ul>
  14. 14. Alternating Current (AC) and Direct Current (DC) <ul><li>Direct current or DC is the first type of current because it is easy to produce. This current always flows in one direction. Its disadvantage is that it has an excessive voltage drop and power loss in the power lines for a long distance. Batteries are common sources of direct current. </li></ul>
  15. 15. <ul><li>Alternating current is the solution to the problem of DC. AC allows the flow of current in two directions. Today, it is possible to step up electricity to a power station, transmit it to any distant place and step it down for consumption. A transformer is the device used for stepping up and stepping down AC voltage. </li></ul>
  16. 16. Graphical Representation of a DC
  17. 17. Graphical Representation of an AC
  18. 18. How Electricity is Delivered to a Customer
  19. 19. What is electrical energy and power? <ul><li>Electrical Energy – the capacity to do electrical work </li></ul><ul><li>Unit: watt-sec, kilowatt-hour, joule </li></ul><ul><li>W = P x t </li></ul><ul><li>Where: W = energy </li></ul><ul><li> P = power </li></ul><ul><li>t = time </li></ul><ul><li>Conversion factor: 1 joule = 10 7 ergs </li></ul>
  20. 20. <ul><li>Electric Power – the rate of doing electrical work or it is the rate at which electrical energy is converted to other forms of energy. </li></ul><ul><li>Unit: joule/sec, watt </li></ul><ul><li>P = work/time = EI = E2/R = I2R </li></ul><ul><li>Where E = voltage </li></ul><ul><li> I = current </li></ul><ul><li>R = resistance </li></ul>
  21. 21. What is voltage? <ul><li>Voltage - (potential Difference) or (electromotive force) – the force or pressure which makes electrons moves or tends to move from atom to atom along the wire. </li></ul><ul><li>Unit: volts </li></ul>
  22. 22. What are current and resistance? <ul><li>Current – the rate of flow of electrons per unit of time. It can be direct current or alternating current. </li></ul><ul><li>Unit: Ampere </li></ul><ul><li>Resistance– the capability of the resistor to limit the flow of current and reduce the amount of voltage in a circuit. </li></ul><ul><li>Unit: ohms,  </li></ul>
  23. 23. Ohm’s Law <ul><li>The current is directly proportional to the voltage across the resistance and inversely proportional to the resistance. </li></ul><ul><li>V </li></ul><ul><li>I = ----- </li></ul><ul><li>R </li></ul><ul><li>Power Relationship: P = VI </li></ul>
  24. 25. Mathematical Prefixes <ul><li>Giga = x10 9 </li></ul><ul><li>Mega = x10 6 </li></ul><ul><li>Kilo = x10 3 </li></ul><ul><li>milli = x10 -3 </li></ul><ul><li>micro = x10 -6 </li></ul><ul><li>nano = x10 -9 </li></ul><ul><li>pico = x10 -12 </li></ul>
  25. 26. Conversion to Prefixes and Scientific Notations <ul><li>25000000V </li></ul><ul><li>0.0000067A </li></ul><ul><li>1250000 meters </li></ul><ul><li>0.005 liters </li></ul><ul><li>2.4x10 3 meters </li></ul><ul><li>33x10 -6 watts </li></ul><ul><li>0.00045 A </li></ul><ul><li>6.6x10 6 Ω </li></ul>
  26. 27. EXERCISES 300W 12V 120W 1.2 Ω 260W 10A 3 Ω 30V 10 Ω 24A POWER RESISTANCE CURRENT VOLTAGE
  27. 28. Basic Electrical Variables Seimens, mho G Conductance Ohms R Resistance Joule W Energy Watts P Power Volts V Voltage Ampere I Current Coulomb Q Charge sec t Time Unit Symbol Variable
  28. 29. Examples <ul><li>A simple circuit has 12V and a resistance of 4.7K  . Determine the current and power of the circuit. </li></ul><ul><li>2. The output current of a certain integrated circuit is 6mA and it is flowing into a resistance of 5K  . Determine the voltage across the resistance. </li></ul>
  29. 30. <ul><li>3. Determine the hot resistance of a 60watts bulb operated from an effective voltage of 120V. </li></ul><ul><li>4. The power dissipated in a certain resistance is 100watts and the current is 4A. Determine the resistance. </li></ul>
  30. 31. <ul><li>5. Assume that a family leaves a 60watts light bulb on for a duration of a two weeks trip. If electricity cost 9 cents per kilowatt-hour, determine the cost incurred. </li></ul>
  31. 32. Assignment no. 1 <ul><li>Research on the following scientist and state what invention he contributed in the field of electronics </li></ul><ul><li>Cuneus and Muschenbrock </li></ul><ul><li>Benjamin Franklin </li></ul><ul><li>Charles Augustus Coulomb </li></ul><ul><li>Luigi Galvani </li></ul><ul><li>Alessandro Volta </li></ul><ul><li>Hans Christian Oersted </li></ul><ul><li>Andre Marie Ampere </li></ul>
  32. 33. <ul><li>8. Georg Simon Ohm </li></ul><ul><li>9. Michael Faraday </li></ul><ul><li>10. Karl Friedrich Gauss and Wilhelm Eduard Weber </li></ul><ul><li>11. Joseph Henry </li></ul><ul><li>12. Heinrich Lenz </li></ul><ul><li>13. Samuel Finley Breese Morse </li></ul><ul><li>14. Gustav Robert Kirchhoff </li></ul><ul><li>15. James Clerk Maxwell </li></ul><ul><li>16. Joseph Wilson Swan </li></ul><ul><li>17. Thomas Alva Edison </li></ul><ul><li>18. Heinrich Rudolf Hertz </li></ul><ul><li>19. Nikola Tesla </li></ul><ul><li>20. Guglielmo Marconi </li></ul>
  33. 34. <ul><li>21. Albert Einstein </li></ul><ul><li>22. Shockley, Bardeen and Brattain </li></ul><ul><li>23. Jack Kilby </li></ul><ul><li>24. Robert Norton Noyce </li></ul><ul><li>25. Seymour Cray </li></ul>
  34. 35. II. Complete the Table below, show your solutions 3W 100 Ω 12V 10mA 13.75V 22 Ω 220W 2.4A power voltage current resistance
  35. 36. III. Problem Solving <ul><li>What is the power in a circuit if the secondary transformer rated at 12V, 2A? </li></ul><ul><li>How much is the power loss of 100 Ω resistance, which consumes current of 10A? </li></ul><ul><li>How much current is flowing in a 1KΩ resistor with an input voltage of 12V? </li></ul><ul><li>How much resistance is needed to absorbed a current of 2.5mA with a voltage of 3V? </li></ul>
  36. 37. Resistor Color Code Temp coef 6 th band tolerance tolerance 5 th band Multiplier Multiplier tolerance 4 th band Significant figure Significant figure Multiplier 3 rd band Significant figure Significant figure Significant figure 2 nd band Significant figure Significant figure Significant figure 1 st band 6 bands 5 bands 4 bands designation
  37. 38. Resistor Color Code +/- 0.5% 100000 5 Green 25 10000 4 Yellow 15 1000 3 Orange 50 +/- 2% 100 2 Red 100 +/- 1% 10 1 Brown 1 0 Black TC TOL multiplier SF Color
  38. 39. +/- 10% 10 -2 Silver +/- 5% 10 -1 Gold 1 10 9 9 White +/- 0.05% 10 8 8 Grey 5 +/- 0.1% 10 7 7 Violet 10 +/- 0.25% 10 6 6 Blue
  39. 40. Exercises <ul><li>Decode the following resistor color. </li></ul><ul><li>red, blue, violet, green </li></ul><ul><li>Blue, black, red, red </li></ul><ul><li>Yellow, red, orange, silver </li></ul><ul><li>Blue, black, black, red, red </li></ul><ul><li>Green, red, red, green, blue </li></ul><ul><li>Grey, green, silver, green </li></ul><ul><li>Yellow, green, black, white, gold </li></ul><ul><li>Blue, green, violet, red, orange, red </li></ul>
  40. 41. Assignment no. 1 <ul><li>Research on the life of at list 10 scientist who contributed in the field of electrical, electronics, computer science and information technology. </li></ul><ul><li>Decode the following color coded resistor. </li></ul><ul><li>red, green, blue, violet </li></ul><ul><li>Yellow, green, silver, blue </li></ul><ul><li>Blue, yellow, orange, green, red </li></ul><ul><li>Red, blue, blue, red, orange </li></ul><ul><li>Violet, black, white, blue </li></ul>
  41. 42. <ul><li>III. Problem Solving: </li></ul><ul><li>1. Convert 2.5x10 7 ergs to joules. </li></ul><ul><li>Convert 1.2kw-hr to watt-sec </li></ul><ul><li>Convert 4 joules to ergs </li></ul><ul><li>A lamp operating at 120 volts has a resistance of 200  , what is the power used? </li></ul><ul><li>An electric flat iron draws 11A at a source of 120V. What is the power? </li></ul>
  42. 43. <ul><li>6. A simple machine operates at 210watts at 240 volts, what is its resistance and power? </li></ul>
  43. 44. Resistivity <ul><li>FACTORS GOVERNING THE RESISTANCE OF MATERIALS OR ELECTRIC CONDUCTORS: </li></ul><ul><li>The resistance of different materials varies greatly. Some such as the metals conducts electricity very readily and hence called conductors. Others, such as wood or plates, at least when moist, are partial conductors. Still others, such as glass, porcelain and paraffin, are called insulators because they are practically non-conducting. </li></ul><ul><li>The resistance of an electric conductor depends upon the following: </li></ul><ul><li>Type of conductor material </li></ul><ul><li>Length of the conductor </li></ul><ul><li>Cross sectional area of the conductor </li></ul><ul><li>Temperature </li></ul><ul><li>Distributing of current </li></ul>
  44. 45. Series Parallel Resistors <ul><li>Series Resistors: </li></ul><ul><li>Conditions: </li></ul><ul><li>The total resistance of a series resistors is the sum of the individual resistances. </li></ul><ul><li>The total voltage of a series resistors is the sum of individual voltages or voltage drops in each resistor. </li></ul><ul><li>The total current of a series resistors is equal to the individual current in each resistors. </li></ul>
  45. 47. <ul><li>Equations: </li></ul><ul><li>Vt = VR1 + VR2 + VR3 </li></ul><ul><li>= I1R1 + I2R2 + I3R3 </li></ul><ul><li>Rt = R1 + R2 + R3 </li></ul><ul><li>It = I1 = I2 = I3 </li></ul>
  46. 48. <ul><li>Power Equation </li></ul><ul><li>Pt = P1 + P2 + P3 </li></ul><ul><li>The total power in a series resistors is equal to the sum of the individual power in each resistor. </li></ul>
  47. 49. Example <ul><li>Determine the total resistance, total current and current and voltage in each resistor of the circuit below </li></ul>
  48. 50. 2. Find Rx for the circuit shown below
  49. 51. <ul><li>Determine the voltage and power in each resistor below. Find the input voltage. </li></ul>
  50. 52. Assignment no. 3 <ul><li>4. Find Vt,P1, R1, V2, P2, R3, V3 and Pt for the circuit shown. </li></ul>
  51. 53. <ul><li>Parallel Resistors: </li></ul><ul><li>Conditions: </li></ul><ul><li>The total resistance is equal to the sum of the inverse of the resistances. </li></ul><ul><li>The total current is equal to the sum of the current in each resistor. </li></ul><ul><li>The voltages in each parallel resistor are equal. </li></ul>
  52. 55. Equations <ul><li>Vt = VR1 = VR2 = VR3 </li></ul><ul><li>1 1 1 1 </li></ul><ul><li>---- = ------ + ------ + ------- </li></ul><ul><li>Rt R1 R2 R3 </li></ul><ul><li>It = I1 + I2 + I3 </li></ul>
  53. 56. Exercises <ul><li>Find the total resistance of the given parallel resistors. </li></ul>
  54. 57. 2. Determine the total resistance of the given parallel resistors
  55. 58. 3. Find Rx for the parallel resistor below
  56. 59. Assignment no. 4 4. Find the total resistance and current, voltage and power in each resistor below
  57. 60. Series-parallel resistor <ul><li>Find the total resistance of the circuit below: </li></ul>
  58. 61. 2 . Find the total resistance of the circuit below. Determine the total current and power.
  59. 62. 3. Find the total resistance of the circuit below.
  60. 63. 4. Find the total resistance of the circuit below.
  61. 64. Assignment no. 5 <ul><li>1. Find the total current and resistance of the circuit below. </li></ul>
  62. 65. Series Parallel Capacitor <ul><li>For series capacitor: </li></ul><ul><li>1/Ct = 1/C1 + 1/C2 + 1/C3 </li></ul>
  63. 66. For parallel capacitor: <ul><li>Ct = C1 + C2 + C3 </li></ul>
  64. 67. Series Parallel Inductor For series inductor <ul><li>Lt = L1 + L2 + L3 </li></ul>
  65. 68. For parallel inductor 1/Lt = 1/L1 + 1/L2 + 1/L3
  66. 69. Exercises Determine the total capacitance or inductance of the circuit below <ul><li>1. </li></ul>
  67. 70. <ul><li>2. Find the total inductance. </li></ul>
  68. 71. Assignment no. 6 <ul><li>Find the total inductance of the circuit below </li></ul>
  69. 72. <ul><li>2. Change the inductor in problem 1 with Farad and determine the total capacitance. </li></ul>
  70. 73. Magnetism <ul><li>What is a magnet? </li></ul><ul><li>A magnet is an object made of certain materials which create a magnetic field .  Every magnet has at least one north pole and one south pole.  By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet.  This is an example of a magnetic dipole (&quot;di&quot; means two, thus two poles).  If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole.  If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole.  No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole.  </li></ul>
  71. 74. <ul><li>The ancient Greeks and Chinese discovered that certain rare stones, called lodestones, were naturally magnetized.  These stones could attract small pieces of iron in a magical way, and were found to always point in the same direction when allowed to swing freely suspended by a piece of string.  The name comes from Magnesia, a district in Thessaly, Greece </li></ul>
  72. 75. <ul><li>Things that uses magnet: </li></ul><ul><li>Headphones, stereo speakers, telephone receivers, phone ringers, microwave tubes, doorbell ringer solenoid, floppy disk recording and reading head, credit card, computer monitor deflection coil, computer hard drive recording, TV deflection coil, clothes washer and dryer, DVD spinner and head positioner, hard disk spinner, starter motor, A/C clutch, etc. </li></ul>
  73. 76. Ten facts about magnet <ul><li>1. North poles point north, south poles point south. </li></ul><ul><li>2. Like poles repel, unlike poles attract. </li></ul><ul><li>3. Magnetic forces attract only magnetic materials. </li></ul><ul><li>4. Magnetic forces act at a distance. </li></ul><ul><li>5. While magnetized, temporary magnets act like permanent magnets. </li></ul><ul><li>6. A coil of wire with an electric current flowing through it becomes a magnet. </li></ul><ul><li>7. Putting iron inside a current-carrying coil increases the strength of the electromagnet. </li></ul><ul><li>8. A changing magnetic field induces an electric current in a conductor. </li></ul><ul><li>9. A charged particle experiences no magnetic force when moving parallel to a magnetic field, but when it is moving perpendicular to the field it experiences a force perpendicular to both the field and the direction of motion. </li></ul><ul><li>10. A current-carrying wire in a perpendicular magnetic field experiences a force in a direction perpendicular to both the wire and the field. </li></ul>
  74. 77. Types of magnets <ul><li>Permanent magnet </li></ul><ul><li>Temporary magnets </li></ul><ul><li>Electromagnets </li></ul>
  75. 78. <ul><li>Permanent Magnets </li></ul><ul><li>Permanent magnets are those we are most familiar with, such as the magnets hanging onto our refrigerator doors.  They are permanent in the sense that once they are magnetized, they retain a level of magnetism.  As we will see, different types of permanent magnets have different characteristics or properties concerning how easily they can be demagnetized, how strong they can be, how their strength varies with temperature, and so on. </li></ul><ul><li>Temporary Magnets </li></ul><ul><li>Temporary magnets are those which act like a permanent magnet when they are within a strong magnetic field, but lose their magnetism when the magnetic field disappears.  Examples would be paperclips and nails and other soft iron items. </li></ul>
  76. 79. <ul><li>Electromagnets </li></ul><ul><li>An electromagnet is a tightly wound helical coil of wire, usually with an iron core, which acts like a permanent magnet when current is flowing in the wire.  The strength and polarity of the magnetic field created by the electromagnet are adjustable by changing the magnitude of the current flowing through the wire and by changing the direction of the current flow. </li></ul><ul><li>Neodymium Iron Boron magnet = Nd2Fe14B or Nd15Fe77B8. </li></ul>
  77. 80. Coulomb’s law <ul><li>The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each of the charges and inversely proportional to the square of the total distance between the two charges . </li></ul><ul><li>k Q1Q2 </li></ul><ul><li>F = -------------- where k = 8.99E9 Nm2/C2 </li></ul><ul><li>r2 </li></ul>
  78. 81. <ul><li>K = 1 / 4  o </li></ul><ul><li>But  = 8.854x10E-12 </li></ul>
  79. 82. Examples <ul><li>Two charges of +1C each is separated at a distance of 1meter. Determine the force of repulsion of the two charge. </li></ul><ul><li>Two balloons are charge with identical quantity of -6.25uC. They are separated with a distance of 66.67cm. Determine the force of repulsion of the two balloons. </li></ul>
  80. 83. <ul><li>Two charges +1.2uC and -2.4uC are separated with a distance of 2m. Determine the force of attraction of the two charges. </li></ul><ul><li>The force of attraction between a +2.2uC and an unknown charge is 1.2N. They are separated by 120cm distance. Find the charge of the other electron. </li></ul>
  81. 84. <ul><li>Given the figure below: </li></ul><ul><li>Find the total force of the two charges on charge -3.3uC. Which has greater force of attraction? </li></ul>
  82. 85. Assignment no. 7 <ul><li>Two charges, -10uC and +15uC, are acting on a force of attraction of 4.5N. Determine their distances. </li></ul><ul><li>Two point charges, +25nC and -75nC, are 10cm apart. Determine the force of attraction between them. </li></ul>
  83. 86. <ul><li>Determine the force of attraction of two negatively charge particle to the positively charge particle. Determine total force. </li></ul>
  84. 87. 4. Find the total force develop by three positive charge to the negative charge particle in the figure
  85. 88. Semiconductor Materials <ul><li>Semiconductors conduct less than metal conductors but more than insulators. </li></ul><ul><li>Some common semiconductor materials are silicon (Si), germanium (Ge), and carbon (C) . </li></ul><ul><li>Silicon is the most widely used semiconductor material in the electronics industry. </li></ul><ul><li>Almost all diodes, transistors, and ICs manufactured today are made from silicon. </li></ul>
  86. 89. <ul><li>Intrinsic semiconductors are semiconductors in their purest form. </li></ul><ul><li>Extrinsic semiconductors are semiconductors with other atoms mixed in. </li></ul><ul><li>These other atoms are called impurity atoms. </li></ul><ul><li>The process of adding impurity atoms is called doping. </li></ul>
  87. 90. The figure below illustrates a bonding diagram of a silicon crystal.
  88. 91. <ul><li>Thermal energy is the main cause for the creation of an electron-hole pair, as shown in Figure </li></ul><ul><li>As temperature increases, more thermally generated electron-hole pairs are created. </li></ul><ul><li>In the figure, the hole acts like a positive charge because it attracts a free electron passing through the crystal. </li></ul>
  89. 92. <ul><li>The figure shows the doping of a silicon crystal with a pentavalent impurity.(N type) </li></ul><ul><li>Arsenic (As) is shown in this figure, but other pentavalent impurities such as antimony (Sb) or phosphorous (P) could also be used. </li></ul>
  90. 93. <ul><li>The figure shows the doping of a silicon crystal with a trivalent impurity.(P type) </li></ul><ul><li>Aluminum (Al) is shown in this figure, but other trivalent impurities such as boron (B) or gallium (Ga) could also be used. </li></ul>
  91. 94. <ul><li>A popular semiconductor device called a diode is made by joining p- and n-type semiconductor materials, as shown in Fig. a. </li></ul><ul><li>The doped regions meet to form a p-n junction. </li></ul><ul><li>Diodes are unidirectional devices that allow current to flow in one direction. </li></ul><ul><li>The schematic symbol for a diode is shown in Fig. b. </li></ul>
  92. 95. The PN junction
  93. 96. Biasing of Diodes <ul><li>Forward bias </li></ul><ul><li>Reverse bias </li></ul>
  94. 97. Volt-Ampere Characteristic Curve
  95. 98. <ul><li>Previous slide is a graph of diode current versus diode voltage for a silicon diode. </li></ul><ul><li>The graph includes the diode current for both forward- and reverse-bias voltages. </li></ul><ul><li>The upper right quadrant of the graph represents the forward-bias condition. </li></ul><ul><li>Beyond 0.6 V of forward bias the diode current increases sharply. </li></ul><ul><li>The lower left quadrant of the graph represents the reverse-bias condition. </li></ul><ul><li>Only a small current flows until breakdown is reached. </li></ul>
  96. 99. Diode Approximations <ul><li>First approximation(switch) </li></ul><ul><li>Second approximation(voltage Ge=0.3V, Si=0.7V) </li></ul><ul><li>3. Third approximation(with internal resistance called bulk resistance) </li></ul>
  97. 100. Polarity of Diodes
  98. 101. Diode Application <ul><li>Determine whether the diode is forward or reverse bias. </li></ul><ul><li>1. </li></ul>
  99. 102. <ul><li>2. </li></ul>
  100. 103. <ul><li>Find the current and the voltage across the load if possible. </li></ul>
  101. 104. <ul><li>4. </li></ul>
  102. 105. <ul><li>5. Find the voltage and current in 1K Ω </li></ul>
  103. 106. <ul><li>6.Determine the current and voltage across 1.5K Ω </li></ul>
  104. 107. <ul><li>7. Determine which switch will turn “ON” the LED.(all diode are silicon) </li></ul>
  105. 108. <ul><li>Find the output voltage </li></ul>
  106. 109. Assignment no. 8 <ul><li>Determine whether the diode is in forward or reverse bias. Why? </li></ul>
  107. 110. <ul><li>Identify the switches that will make the LED to “ON” </li></ul>
  108. 111. 3. Find the output voltage Vo
  109. 112. 4. Find the current and voltage across 2K Ω
  110. 113. Special types of diodes <ul><li>Zener diode – a silicon pn junction device that differs from rectifier diode because it is designed for operation in the reverse breakdown region. </li></ul><ul><li>Symbol: </li></ul>
  111. 114. <ul><li>2. LED(light emitting diode) – it is made of gallium arsenide or gallium arsenide phosphide. </li></ul><ul><li>Operation: when the device is forward bias, electrons cross the pn junction from the n type material to p type material. When recombination takes place, the electrons release energy in the form of heat and light. </li></ul>
  112. 115. <ul><li>3. photodiode- a pn junction that operates in reverse bias. It has a small transparent window that allows light to strike the pn junction. </li></ul>
  113. 116. <ul><li>Current regulator diode - it maintain a constant current as the zener diode maintain constant voltage. </li></ul>
  114. 117. <ul><li>5. Varicap (variable capacitor) </li></ul>
  115. 118. <ul><li>Transistor- a three terminal device used for signal amplification. </li></ul><ul><li>Three parts: collector, base and emitter </li></ul><ul><li>Two types: bipolar junction transistor </li></ul><ul><li>field effect transistor </li></ul><ul><li>Types of transistor: pnp and npn </li></ul>
  116. 119. <ul><li>Symbol: </li></ul><ul><li>NPN PNP </li></ul>
  117. 120. <ul><li>Construction: </li></ul>
  118. 121. <ul><li>Diode equivalent </li></ul>
  119. 122. <ul><li>Transistor configuration: </li></ul><ul><li>Common base </li></ul><ul><li>Common collector </li></ul><ul><li>Common emitter </li></ul><ul><li>Current consideration: Ic + Ib = Ie </li></ul>
  120. 123. <ul><li>Transistor parameters: </li></ul><ul><li>Alpha and beta </li></ul>
  121. 124. <ul><li>BJT proper biasing </li></ul><ul><li>Mode e-b jct. c-b jct. Use </li></ul><ul><li>Active forward reverse amplifier </li></ul><ul><li>Cutoff reverse reverse switch, off pos. </li></ul><ul><li>Saturation forward forward switch, on pos. </li></ul>
  122. 125. <ul><li>Transistor characteristics curve: </li></ul>
  123. 126. <ul><li>Simple transistor circuit: </li></ul>
  124. 127. Logic gates and Boolean Algebra <ul><li>Boolean algebra(logic operation) </li></ul><ul><li>1+1=1 </li></ul><ul><li>1+0=1 </li></ul><ul><li>0+0=0 </li></ul><ul><li>1x1=1 </li></ul><ul><li>1x0=0 </li></ul><ul><li>1’ = 0 </li></ul><ul><li>Binary addition : 1+1 = 10 </li></ul>
  125. 128. <ul><li>Perform binary addition for the following: </li></ul><ul><li>11101101 </li></ul><ul><li>+ 1011101 </li></ul><ul><li>101011111 </li></ul><ul><li>+ 111101101 </li></ul>
  126. 129. <ul><li>Use truth table to simplify the given expression. </li></ul><ul><li>Y = A’ + BC’ </li></ul><ul><li>Y = (AB)’(A+C)’ </li></ul><ul><li>Y = A + A’(A) </li></ul><ul><li>Y = B’ </li></ul>