Electronic devices chapter 1- 3 (m.sc physics)

Foundation of Engineering

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Electronic Devices & Circuits

About MeAatif Saeed EducationM.Sc ElectronicsM.Sc Systems EngineeringMS Project Management Experience16+ Years Teaching 14+ Years Industry Projects Email [email protected]

Course OutlineChapter 1 12Marks DistributionAssignments 10%Quizzes 10%Class Participation 5%Mid Term 25%Final 50%Final Examination Question Paper 8 Review Questions out of 12

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Course BreakupChapter #Final Exam Q. NoChapter Heading1Introduction to Electronics2Diodes and Applications 3Special Purpose Diodes4Bipolar Junction Transistors5Transistor Bias Circuits 6BJT Amplifiers 7Power Amplifiers8Field Effect Transistors (FETs)9FET Amplifiers and Switching Circuits

Course BreakupChapter #Final Exam Q. NoChapter Heading10Amplifier Frequency Response11Thyristors12Operational Amplifiers

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Text BookElectronic Devices 9th Edition Thomas L. Floyd

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Chapter 1Introduction to Electronics

The Start of the Modern Electronics Era

Bardeen, Shockley, and Brattain at Bell Labs - Brattain and Bardeen invented the bipolar transistor in 1947.The first germanium bipolar transistor. Roughly 50 years later, electronics account for 10% (4 trillion dollars) of the world GDP.

Electronics MilestonesBraun invents the solid-state rectifier.DeForest invents triode vacuum tube.1907-1927First radio circuits developed from diodes and triodes.1925Lilienfeld field-effect device patent filed.Bardeen and Brattain at Bell Laboratories invent bipolar transistors.Commercial bipolar transistor production at Texas Instruments.Bardeen, Brattain, and Shockley receive Nobel prize.

Integrated circuits developed by Kilby and NoyceFirst commercial IC from Fairchild SemiconductorIEEE formed from merger of IRE and AIEEFirst commercial IC opampOne transistor DRAM cell invented by Dennard at IBM.4004 Intel microprocessor introduced.First commercial 1-kilobit memory.19748080 microprocessor introduced.Megabit memory chip introduced.2000Alferov, Kilby, and Kromer share Nobel prize

Evolution of Electronic Devices

VacuumTubesDiscreteTransistorsSSI and MSIIntegratedCircuitsVLSISurface-MountCircuits

Introduction to ElectronicsTypes of ElectricityTwo forms of electricity Static and ProducedStatic Electricity is an electrical charge at rest.Produced Electricity is produced by either magnetism, chemicals, light, heat, or pressure.

Introduction to Electronics

Step 1: Basics of ElectricityStep 1: Basics of ElectricityCurrent Andre AmpereVoltage Alessandro VoltaResistance George OhmPower James Watt

CurrentVoltagePowerResistance

Andre Ampere

Alessandro Volta

Georg Ohm

James Watt

Step 2: Electronic Components

CurrentVoltagePowerResistanceComponents Step 2: Electronic Components Switches and Keyboard Semiconductors Transducers Resistors Capacitors Electron Tubes Magnetic

Nikola Tesla

Thomas Edison

Step 3: Electronic Circuits

CurrentVotlagePowerResistance

ComponentsCircuits Step 3: Electronic CircuitsSignal Generators and TimersAmplifiersDigital CircuitsPower SuppliesDetectors and MixersFiltersPhase-locked LooksConvertersData AcquisitionSynthesizers

Charles Wheatstone

Gustav Kirchoff

Robert Noyce

Step 4: Electronic Systems


ComponentsCircuitsSystems Step 4: Electronic SystemsCommunicationsComputersConsumerIndustrialTest and MeasurementBiomedical

Step 4: Electronic SystemsCommunications SystemsRadioTelecommunicationsTelevisionData Communications


ComponentsCircuitsSystemsCommunications

Heinrich Hertz

Guglielmo Marconi

Lee Deforest

John Baird



ComponentsCircuitsSystemsCommunicationComputers Computers Data Terminals Computer Systems Data Storage Input/Output Devices

George Boole

John von Neuman

Alan Turing

Charles Babbage


CurrentVotlagePowerResistanceComponentsCircuitsSystemsCommunicationComputersConsumer Consumer Video Equipment Audio Equipment Personal Automobile Electronics

William Shockley

Chester Carlson

Jack Kilby

Nolan Bushnell



ComponentsCircuitsSystemsCommunicationComputersConsumerIndustrial Industrial Manufacturing Equipment Computer-Aided-Design and Engineering CAD/CAE Management

Charles Steinmetz

Werner Von Siemens

James Joule

Carl Gauss



Test and Measurement General Test and Measurement Equipment Automated Test SystemsComponentsCircuitsSystemsCommunicationComputersConsumerIndustrialTest and Measurement

Sir Isaac Newton

RAdm Grace Harper

Benjamin Franklin

John Napier


CurrentVotlagePowerResistance Biomedical Patient Care DiagnosticsCircuitsComponentsSystemsCommunicationComputersConsumerIndustrialTest and MeasurementBiomedical

Luigi Galvani

Henry Cavendish

Sir John Fleming

Chapter 1Introduction to Electronics

The Bohr atomThe nucleus is positively charged and has the protons and neutrons.

The atomic number is the number of protons and determines the particular element.In the neutral atom, the number of electrons is equal to the number of protons. Electrons are negatively charged and in discrete shells.The Bohr atom is useful for visualizing atomic structure.

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A neutral Si atom is shown. There are 4 electrons in the valence shell.Question:Is Si a conductor, insulator, or semiconductor? Semiconductor

The valence shellThe outer shell is called the valence shell. Electrons in this shell are involved in chemical reactions and they account for electrical and thermal conductivity in metals.

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Sodium is highly reactive, and easily gives up its single valence electron. For this reason, it is not used in electrical work.

The valence shellMetals have one, two or three electrons in the valence shell. The atom illustrated here is a sodium atom (Na), with only one electron in its outer shell.

Sodium atomNon-metals have either complete or nearly compete outer shells, so they make poor electrical conductors.

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Electrons and ShellsEnergy LevelsElectrons near the nucleus have less energy than those in more distant orbits. Only discrete (separate and distinct) values of electron energies exist within atomic structures.In an atom, the orbits are grouped into energy levels known as Shells. A given atom has a fixed number of shells. Each shell has a fixed maximum number of electrons. The shells (energy levels) are designated 1, 2, 3, and so on, with 1 being closest to the nucleus.

Electrons and Shells

Electrons and ShellsMax. # of Electrons in Each Shell

Valence Electrons. This outermost shell is known as the valence shell and electrons in this shell are called valence electrons.

IonizationIf a valence electron acquires a sufficient amount of energy, called ionization energy, it can actually escape from the outer shell and the atoms influence. The departure of a valence electron leaves a previously neutral atom with an excess of positive charge (more protons than electrons). The process of losing a valence electron is known as ionization, and the resulting positively charged atom is called a positive ion.

The Quantum ModelEach shell or energy level consists of up to four subshells called orbitals, which are designated s, p, d, and f.Orbital s can hold a maximum of two electrons, orbital p can hold six electrons, orbital d can hold ten electrons, and orbital f can hold fourteen electrons.

The Quantum Model

The Quantum Model

Materials Used In ElectronicsInsulators An insulator is a material that does not conduct electrical current under normal conditions. Most good insulators are compounds rather than single-element materials and have very high resistivities. Valence electrons are tightly bound to the atoms; therefore, there are very few free electrons in an insulator. Examples of insulators are rubber, plastics, glass, mica, and quartz.

Materials Used In ElectronicsConductors A conductor is a material that easily conducts electrical current. Most metals are good conductors. The best conductors are single-element materials, such as copper (Cu), silver (Ag), gold (Au), and aluminum (Al), which are characterized by atoms with only one valence electron very loosely bound to the atom.

Materials Used In ElectronicsSemiconductors A semiconductor is a material that is between conductors and insulators in its ability to conduct electrical current. A semiconductor in its pure (intrinsic) state is neither a good conductor nor a good insulator. Single-element semiconductors are antimony (Sb), arsenic (As), astatine (At), boron (B), polonium (Po), tellurium (Te), silicon (Si), and germanium (Ge).

Materials Used In ElectronicsSemiconductors Compound semiconductors such as gallium arsenide, indium phosphide, gallium nitride, silicon carbide, and silicon germanium are also commonly used. The single-element semiconductors are characterized by atoms with four valence electrons. Silicon is the most commonly used semiconductor.

Band GapValence shell of an atom represents a band of energy levels and that the valence electrons are confined to that band.When an electron acquires enough additional energy, it can leave the valence shell, become a free electron, and exist in what is known as the conduction band.The difference in energy between the valence band and the conduction band is called an energy gap or band gap.

Band Gap

ComparisonSemi-Conductor Atom vs Conductor AtomThe core includes everything except the valence electrons.The core of the silicon atom has a net charge of 4 (14 protons 10 electrons) The core of the copper atom has a net charge of 1 (29 protons 28 electrons)

Comparison

Silicon & Germanium

Silicon & Germanium Both Silicon and Germanium have the characteristic Four Valence electrons.The valence electrons in Germanium are in the fourth shell while those in Silicon are in the third shell, closer to the nucleus Germanium valence electrons are at higher energy levels than those in siliconGermanium more unstable at high temperatures and results in excessive reverse current.

Covalent Bonds

Silicon Crystal

Current In SemiconductorsEnergy band diagram for an unexcited atom in a pure (intrinsic) silicon crystal.

Conduction Electrons and Holes

Conduction Electrons and HolesHoleWhen an electron jumps to the conduction band, a vacancy is left in the valence band within the crystal. Electron-Hole PairFor every electron raised to the conduction band by external energy, there is one hole left in the valence band, creating what is called an electron-hole pair. Recombination occurs when a conduction-band electron loses energy and falls back into a hole in the valence band.

Conduction Electrons and Holes

Electron and Hole CurrentWhen a voltage is applied across a piece of intrinsic silicon, the thermally generated free electrons in the conduction band, which are free to move randomly in the crystal structure, are now easily attracted toward the positive end. This movement of free electrons is one type of current in a semiconductive material and is called electron current.

Electron and Hole Current

N-type And P-type SemiconductorsDopingSince semiconductors are generally poor conductors, their conductivity can be drastically increased by the controlled addition of impurities to the intrinsic (pure) semiconductive material. This process increases the number of current carriers (electrons or holes). The two categories of impurities aren-type and p-type.

N-Type SemiconductorTo increase the number of conduction-band electrons in intrinsic silicon, pentavalent impurity atoms are added. These are atoms with five valence electrons such as arsenic (As), phosphorus (P), bismuth (Bi), and antimony (Sb).

N-Type Semiconductor

Donor Atom

Majority and Minority CarriersSince most of the current carriers are electrons, silicon (or germanium) doped with pentavalent atoms is an n-type semiconductor (the n stands for the negative charge on an electron). The electrons are called the majority carriers in n-type material. Although the majority of current carriers in n-type material are electrons, there are also a few holes that are created when electron-hole pairs are thermally generated. These holes are not produced by the addition of the pentavalent impurity atoms. Holes in an n-type material are called minority carriers.

P-Type SemiconductorTo increase the number of holes in intrinsic silicon, trivalent impurity atoms are added. These are atoms with three valence electrons such as boron (B), indium (In), and gallium (Ga).

P-Type Semiconductor

Acceptor Atom

The PN JunctionWhen you take a block of silicon and dope part of it with a trivalent impurity and the other part with a pentavalent impurity, a boundary called the PN junction is formed between the resulting p-type and n-type portions.

The PN Junction

The PN Junction

Formation of the Depletion RegionWhen the pn junction is formed, the n region loses free electrons as they diffuse across the junction. This creates a layer of positive charges (pentavalent ions) near the junction. As the electrons move across the junction, the p region loses holes as the electrons and holes combine. This creates a layer of negative charges (trivalent ions) near the junction. These two layers of positive and negative charges form the depletion region.

Energy Diagrams of the PN Junction

Energy Diagrams of the PN Junction

Diodes & ApplicationsChapter 2

The Diode A diode is made from a small piece of semiconductor material, usually silicon, in which half is doped as a p region and half is doped as an n region with a pn junction and depletion region in between.

Diode Packages

Forward BiasForward bias is the condition that allows current through the pn junction.

Forward BiasRequirementsNegative side of VBIAS is connected to the n region of the diode and the positive side is connected to the p region. VBIAS >>> Barrier Potential

Effect of Forward Bias on the Depletion RegionAs more electrons flow into the depletion region, the number of positive ions is reduced. As more holes effectively flow into the depletion region on the other side of the pn junction, the number of negative ions is reduced. This reduction in positive and negative ions during forward bias causes the depletion region to narrow

-cont.

Barrier Potential When forward bias is applied, the free electrons are provided with enough energy from the bias-voltage source to overcome the barrier potential and cross the depletion region. The energy that the electrons require in order to pass through the depletion region is equal to the barrier potential. This energy loss results in a voltage drop across the pn junction equal to the barrier potential (0.7 V)

Reverse BiasReverse bias is the condition that essentially prevents current through the diode.

-continued

Reverse CurrentThe extremely small current that exists in reverse bias after the transition current dies out is caused by the minority carriers in the n and p regions that are produced by thermally generated electron-hole pairs.

V-I Characteristic of a Diode

V-I Characteristic of a DiodePoint A corresponds to a zero-bias condition. Point B corresponds to where the forward voltage is less than the barrier potential of 0.7 V. Point C corresponds to where the forward voltage approximately equals the barrier potential.

V-I Characteristic for Reverse Bias

The Complete V-I Characteristic Curve

Diode ApproximationsThe Ideal Diode Model

Diode ApproximationsThe Ideal Diode Model

Diode ApproximationsSince the barrier potential and the forward dynamic resistance are neglected, the diode is assumed to have a zero voltage across it when forward-biasedVF = 0 VForward Current

Reverse Current Neglected

Diode Approximation Practical Diode Model



Applying KVL

Diode Approximation Complete Diode Model

Diode Approximation Complete Diode Model

Diode Approximation Complete Diode Model Formulas

Example 2-1

Solution

Solution

Half-wave RectifiersBecause of their ability to conduct current in one direction and block current in the other direction, diodes are used in circuits called rectifiers that convert ac voltage into dc voltage.Rectifiers are found in all dc power supplies that operate from an ac voltage source.

Half-wave Rectifiers

Half-wave RectifiersThe rectifier converts the ac input voltage to a pulsating dc voltage.The rectifier converts the ac input voltage to a pulsating dc voltage.The regulator is a circuit that maintains a constant dc voltage for variations in the input line voltage or in the load.

Half-Wave Rectifier Operation

Half-wave Rectifier Average Value of the Half-Wave Output Voltage

Example 2-2

Effect of Potential Barrier

Transformer CouplingIt allows the source voltage to be stepped down as needed.The ac source is electrically isolated from the rectifier, thus preventing a shock hazard in the secondary circuit.

Transformer CouplingTurns Ratio = Nsec / NpriTurns Ratio > 1 Step UpTurns Ratio < 1 Step Down Secondary Voltage of Transformer

Example 2-4 (Do it by yourself)

Full-wave RectifiersA full-wave rectifier allows unidirectional (one-way) current through the load during the entire 360o of the input cycle.

Full-wave Rectifier Example 2-5

Center-Tapped Full-Wave Rectifier Operation

Operation

Effect of the Turns Ratio on the Output Voltage

Effect of the Turns Ratio on the Output Voltage

Bridge Full-wave Rectification

Bridge Full-wave Rectification

Example 2-7 (Assignment)

Peak Inverse VoltageFor rectifier applications,peak inverse voltage(PIV) orpeak reverse voltage(PRV) is the maximum value ofreverse voltagewhich occurs at thepeakof the input cycle when the diode isreverse-biased.

Power Supply Filters & RegulatorsA power supply filter ideally eliminates the fluctuations in the output voltage of a half-wave or full-wave rectifier and produces a constant-level dc voltage.A voltage regulator prevents changes in the filtered dc voltage due to variations in input voltage or load.

Power Supply Filters & RegulatorsThe small amount of fluctuation in the filter output voltage is called Ripple.

Capacitor-Input Filter




Ripple Voltage

Example 2-8

Solution

Voltage Regulators

Percent RegulationThe line regulation specifies how much change occurs in the output voltage for a given change in the input voltage. It is typically defined as a ratio of a change in output voltage for a corresponding change in the input voltage expressed as a percentage.

Percent RegulationThe load regulation specifies how much change occurs in the output voltage over a certain range of load current values, usually from minimum current (no load, NL) to maximum current (full load, FL).

Example 2-9

Diode Limiters & ClampersDiode circuits, called limiters or clippers, are sometimes used to clip off portions of signal voltages above or below certain levels. Another type of diode circuit, called a clamper, is used to add or restore a dc level to an electrical signal.

Diode Limiters

Diode LimitersExample 2-10 (do it)

Biased Limiters

Diode ClampersA Clamper adds a dc level to an ac voltage.OperationDuring the negative half cycle of the input signal, the diode conducts and acts like a short circuit. The output voltage Vo 0 volts . The capacitor is charged to the peak value of input voltage Vm. and it behaves like a battery. During the positive half of the input signal, the diode does not conduct and acts as an open circuit. Hence the output voltage Vo Vm+ Vm This gives a positively clamped voltage.

Diode ClampersIf the RC time constant is 100 times the period, the clamping action is excellent. An RC time constant of ten times the period will have a small amount of distortion at the ground level due to the charging current.

The Diode Datasheet

Special Purpose DiodesChapter 3

The Zener DiodeA Zener diode is a Silicon pn junction device that is designed for operation in the reverse-breakdown region.The breakdown voltage of a Zener diode is set by carefully controlling the doping level during manufacture.

V-I Characteristics

Zener BreakdownZener diodes are designed to operate in reverse breakdown. Two types of reverse breakdown in a zener diode are avalanche and ZenerThe avalanche effect, occurs in both rectifier and Zener diodes at a sufficiently high reverse voltage.

Zener BreakdownOccurs in a zener diode at low reverse voltagesA zener diode is heavily doped to reduce the breakdown voltage. This causes a very thin depletion region. As a result, an intense electric field exists within the depletion region. Near the zener breakdown voltage (VZ), the field is intense enough to pull electrons from their valence bands and create current.

Breakdown Characteristics

Breakdown CharacteristicsAs the reverse voltage (VR) is increased, the reverse current (IR) remains extremely small up to the knee of the curve. The reverse current is also called the zener current, IZ. At this point, the breakdown effect begins; the internal zener resistance, also called zener impedance (ZZ), begins to decrease as the reverse current increases rapidly. From the bottom of the knee, the zener breakdown voltage (VZ) remains essentially constant although it increases slightly as the zener current, IZ, increases.

Zener RegulationA zener diode operating in breakdown acts as a voltage regulator because it maintains a nearly constant voltage across its terminals over a specified range of reverse-current values.The zener diode maintains a nearly constant voltage across its terminals for values of reverse current ranging from IZK to IZM.

Zener Equivalent Circuits

Zener Equivalent Circuits

Zener Equivalent CircuitsZener Impedence

Example 3-1

Temperature CoefficientThe temperature coefficient specifies the percent change in zener voltage for each degree Celsius change in temperature.

where VZ is the nominal zener voltage at 25oC the reference temperature of TC is the temperature coefficient, and T is the change in temperature from the reference temperature.

Example 3-2

Zener Power Dissipation and DeratingPower Dissipation

Power Derating

Example 3-3

Zener Diode ApplicationsZener Regulation with a Variable Input VoltageZener diode regulators can provide a reasonably constant dc level at the output, but they are not particularly efficient. For this reason, they are limited to pplications that require only low current to the load.

Zener Diode Applications

Zener Diode ApplicationsZener Regulation with a Variable Load

Zener LimiterIn addition to voltage regulation applications, Zener diodes can be used in ac applications to limit voltage swings to desired levels.

Zener Limiter (a)a zener used to limit the positive peakof a signal voltage to the selected zener voltage. During the negative alternation, the zener acts as a forward-biased diode and limits the negative voltage to -0.7 V.

Zener Limiter (b)When the zener is turned around the negative peak is limited by zener action and the positive voltage is limited to +0.7 V.

Zener Limiter (c)Two back-to-back zeners limit both peaks to the zener voltage. During the positive alternation, D12 is functioning as the zener limiter and D21 is functioning as a forward-biased diode. During the negative alternation, the roles are reversed.

Assignment