Basic Electronics Engineering Introduction

Engineering

1. 1904: the simplest vacuum tube – the diode – was invented by John Fleming. 1907: De Forest invented the triode by inserting a third electrode between cathode and anode. Evolution of Electronics Vacuum tubes 8/23/2023 1

2. Vacuum Tubes 8/23/2023 2

3. Vacuum tubes: audio amplifier 8/23/2023 3

4. ENIAC computer (1946, University of Pennsylvania) 8/23/2023 4

5. heralded as a "Giant Brain" by the press thousand times faster than electro-mechanical computer 17,468 vacuum tubes, 7200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors, 6,000 manual switches, and approximately 5,000,000 hand-soldered joints. consumed 150 kW Input was possible from an IBM card reader 100 kHz clock Several tubes burned out almost every day, leaving it non-functional about half the time. ENIAC computer 8/23/2023 5

6. The vacuum tube was a bulky and fragile device which consumed a significant power. 1947: Shockley, Bardeen, and Brattain at Bell Labs invented the first transistor. The first transistor was a “point contact transistor.” The modern transistor is a junction transistor, and it is monolithic (in the same semiconductor piece). The first transistor 8/23/2023 6

7. The bipolar transistor continues to be an important device both as a discrete device and as part of Integrated Circuits (IC). However, in digital circuits such as processors and memory, the MOS (Metal Oxide Semiconductor) field-effect transistor has surpassed the bipolar transistor because of the high integration density and low power consumption it offers. 1930: patent filed by Lilienfeld for field-effect transistor (FET). 1958: Jack Kilby (Texas Instruments) demonstrated the first integrated circuit (bipolar transistor, resistor, capacitor) fabricated on a single piece of germanium. The rest is history! Semiconductor technology 8/23/2023 7

8. Semiconductor technology 8/23/2023 8

9. Modern semiconductor technology silicon wafer

10. Modern semiconductor technology Diffusion furnace

11. Modern semiconductor technology 8/23/2023 11

12. Modern semiconductor technology 8/23/2023 12

13. Active and passive components BJT, JFET,MOSFET 8/23/2023 13

14. Difference between active & Passive components 1 . Active devices inject power to the circuit, whereas passive devices are incapable of supplying any energy. 2 . Active devices are capable of providing power gain, and passive devices are incapable of providing power gain. 3 . Active devices can control the current (energy) flow within the circuit, whereas passive device cannot control it. 4 . An external power is required to start basic operation of an active device where no extra power is used for passive device . 8/23/2023 14

15. Resistors A passive electrical component with two terminals that are used for either limiting or regulating the flow of electric current in electrical circuits. The main purpose of resistor is to reduce the current flow and to lower the voltage in any particular portion of the circuit. made of copper wires coiled around a ceramic rod and the outer part of the resistor is coated with an insulating paint. The SI unit of resistor is Ohm. 8/23/2023 15

16. Resistors 8/23/2023 16

17. Resistors 8/23/2023 17

18. 8/23/2023 18

19. Capacitors A capacitor is a two-terminal electrical device that can store energy in the form of an electric charge. consists of two electrical conductors that are separated by a distance. The space between the conductors may be filled by vacuum or with an insulating material known as a dielectric. The ability of the capacitor to store charges is known as capacitance. 8/23/2023 19

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22. Inductors An inductor is a passive component that is used in most power electronic circuits to store energy in the form of magnetic energy when electricity is applied to it. One of the key properties of an inductor is that it impedes or opposes any change in the amount of current flowing through it. The inductor is also called a choke, a reactor or just a coil. 8/23/2023 22

23. Inductors 8/23/2023 23

24. Inductors 8/23/2023 24

25. Introduction to semiconductor physics parameter Conductor Semi conductor insulator No. of valance electrons 3 or less than 3 4 5 or more than 5 conductivity high medium negligible Semi Conductor Types Intrinsic Extrinsic P type N type 8/23/2023 25

26. Semi-conductor types Intrinsic Semi-Conductor Dopping Extrinsic Semi-Conductor Intrinsic Semi-Conductor Trivalent Impurity P Type Semi-Conductor Intrinsic Semi-Conductor Pentavalent Impurity N Type Semi-Conductor 8/23/2023 26

27. N type semi-conductor Pentavalent (Donor) impurity Arsenic (As) Phosphorus (P) Antimony(Sb) Bismuth(Bi) 8/23/2023 27

28. P type semi-conductor Trivalent (Acceptor) impurity Boron (B) Indium (In) Gallium(Ga) 8/23/2023 28

29. P-N Junction (Diode) 8/23/2023 29 A diode is a two-terminal unidirectional power electronics device. The semiconductor diode is the first invention in a family of semiconductor electronics devices. Silicon and germanium or germanium arsenide is used to make a diode. A diode allows current to flow only in one direction and it blocks the current in another direction. It offers low resistance (ideally zero) in one direction and it offers a high resistance (ideally infinite) in another direction.

30. P-N Junction (Diode) 8/23/2023 30

31. Depletion Region 8/23/2023 31 The depletion region, also called depletion layer, depletion zone. The combining of electrons and holes depletes the holes in the P-region and the electrons in the N-region near the junction.

32. Formation of depletion layer NO external connections : the excess electrons in the N region cross the junction and combine with the excess holes in the P region. N region loses its electrons ……becomes + vly charged P r e g i o n a cc e pt s t he e l e c t r o n s … … b e c o m es – v l y c ha r g ed At one point , the migratory action is stopped. An additional electrons from the N region are repelled by the net negative charge of the p region. Similarly, An additional holes from the P region are repelled by the net positive charge of the n region. Definition: a creation of a thin layer of each side of the junction which is depleted (emptied) of mobile charge carriers. This is known as DEPLETION LAYER ..Thickness is of the order of 10 -6 meter

33. The depletion layer contains no free and mobile charge carriers but only fixed and immobile ions. Its width depends upon the doping level.. Heavy doped……..thin depletion layer lightly doped……..thick depletion layer

34. POTENTIAL BARRIER The electrons in the N region have to climb the potential hill in order to reach the P region Electrons trying to cross from the N region to P region experience a retarding field of the battery and therefore repelled. Similarly for holes from P region. Potential thus produced are called potential barrier Ge..0.3 V Si ..0.7V

35. P-N Junction (Diode) 8/23/2023 35

36. Diode Working 8/23/2023 36 Forward Bias In forward bias the depletion region shrinks slightly in width. With this shrinking the energy required for charge carriers to cross the depletion region decreases exponentially. As the applied voltage increases, current starts to flow across the junction. The barrier potential of the diode is the voltage at which appreciable current starts to flow through the diode. The barrier potential varies for different materials.

37. Diode Working Reverse Bias 8/23/2023 37 Under reverse bias the depletion region widens and causes the electric field produced by the ions to cancel out the applied reverse bias voltage. A small leakage current, Is (saturation current) flows under reverse bias conditions. This saturation current is made up of electron-hole pairs being produced in the depletion region. Saturation current is sometimes referred to as scale current because of it’s relationship to junction temperature.

38. Voltage Current Characteristic 8/23/2023 38

39. Voltage Current Characteristic 8/23/2023 39 The curve drawn between voltage across the junction along X axis and current through the circuits along the Y axis. They describe the DC behavior of the diode. When it is in forward bias, no current flows until the barrier voltage (0.3 V for Ge ) is overcome. Then the curve has a linear rise and the current increases, with the increase in forward voltage like an ordinary conductor. Above 3 V , the majority carriers passing the junction gain sufficient energy to knock out the valence electrons and raise them to the conduction band. Therefore , the forward current increases sharply .

40. Voltage Current Characteristic 8/23/2023 40 With reverse bias, potential barrier at the junction increased. … junction resistance increase…and prevents current flow. However, the minority carriers are accelerated by the reverse voltage resulting a very small current ( REVERSE CURRENT ) ….in the order of micro amperes. When revrese voltage is increased beyond a value , called breakdown voltage,the reverse current increases sharply and the diode shows almost zero resistance .It is known as avalanche breakdown. Reverse voltage above 25 v destroys the junction permanentaly .

41. Knee voltage T h e m i n i m u m amount of voltage required for conducting the diode is known as “knee voltage” or “threshold voltage” , “cut-in-voltage". The forward voltage at which the current through PN junction starts increasing rapidly is known as knee voltage. Knee voltage of “germanium” diode is 0.3volts Knee voltage of “silicon" diode is 0.7volts

42. Reverse Breakdown As the reverse bias voltage increases, the electric field in the depletion region increases. Eventually, it can become large enough to cause the junction to break down so that a large reverse current flows:

43. Currents in a P-N junction 8/23/2023 43

44. Forward and reverse currents 8/23/2023 44 Ideal Diode Equation Where, I D and V D are the diode current and voltage, respectively q is the charge on the electron n is the ideality factor: n = 1 for indirect semiconductors (Si, Ge, etc.) n = 2 for direct semiconductors (GaAs , InP, etc.) k is Boltzmann’s constant T is temperature in Kelvin kT/q is also known as V th , the thermal voltage. At 300K (room temperature),kT/q = 25.9mV

45. Simplification When V D is negative When V D is positive 8/23/2023 45

46. Diode as a Switch 8/23/2023 46

47. Diode as Rectifier It is a circuit which converts AC into pulsating DC Rectifier HWR FWR Centre Tap FWR Bridge 8/23/2023 47

48. Half Wave Rectifier 8/23/2023 48

49. Half Wave Rectifier 8/23/2023 49

50. Half Wave Rectifier 8/23/2023 50

51. Half Wave Rectifier 8/23/2023 51

52. Half Wave Rectifier Average or DC Load Current Average or DC Load Voltage RMS Current RMS Voltage Form Factor 8/23/2023 52

53. Half Wave Rectifier Ripple Factor = 1.21 or 121 % DC output Power AC Input Power Efficiency Peak Inverse Voltage 8/23/2023 53

54. Center Tapped –Full Wave Rectifier 8/23/2023 54

55. Center Tapped –Full Wave Rectifier 8/23/2023 55

56. Center Tapped –Full Wave Rectifier 8/23/2023 56 Average or DC Load Current Average or DC Load Current RMS Current RMS Voltage Form Factor

57. Center Tapped –Full Wave Rectifier Ripple Factor = 0.482 or 48.2 % DC output Power AC Output Power Efficiency Peak Inverse Voltage 8/23/2023 57

58. Bridge Rectifier 8/23/2023 58

59. Bridge Rectifier 8/23/2023 59

60. Bridge Rectifier 8/23/2023 60 Average or DC Load Current Average or DC Load Current RMS Current RMS Voltage Form Factor

61. Bridge Rectifier Ripple Factor = 0.482 or 48.2 % DC output Power AC Output Power Efficiency Peak Inverse Voltage 8/23/2023 61

62. Comparison of HWR and FWR 8/23/2023 62

63. Special Purpose Diode: Zener Diode 8/23/2023 63

64. Features: Uses the relatively constant reverse breakdown voltage to produce a voltage reference. Breakdown voltage is called the Zener voltage , V Z Output voltage of circuit shown is equal to V Z despite variations in input voltage V A resistor is used to limit the current in the diode 8/23/2023 64 Special Purpose Diode: Zener Diode

65. Zener Diode as Voltage Regulator 8/23/2023 65

66. Difference between Avalanche and Zener breakdown 8/23/2023 66

67. Light Emitting Diode (LED) 8/23/2023 67

68. Special-Purpose Diodes Light-emitting diodes discussed earlier when we looked at light actuators 8/23/2023 68

69. LED Working 8/23/2023 69

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71. Photo Diode 8/23/2023 71

72. Photo Diode Characteristics 8/23/2023 72

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74. Key Points Diodes allow current to flow in only one direction At low temperatures semiconductors act like insulators At higher temperatures they begin to conduct Doping of semiconductors leads to the production of p- type and n -type materials A junction between p- type and n -type semiconductors has the properties of a diode Silicon semiconductor diodes approximate the behavior of ideal diodes but have a conduction voltage of about 0.7 V There are also a wide range of special purpose diodes Diodes are used in a range of applications 8/23/2023 74

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