Lecture 1 Electronics

8/6/2019 Lecture 1 Electronics

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Basic electronicsBasic electronics


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ElectricityElectricity ElectricityElectricity isis aa formform of of energyenergy thatthat cancan produceproduce light,light, heat,heat, magnetism,magnetism,

chemicalchemical changeschanges.. ItIt isis thethe secondsecond energyenergy source,source, whichwhich meansmeans thatthat wewe getget ititfromfrom thethe conversionconversion ofof otherother energyenergy sourcesource..

One might define electricity as the separation of positive and negative electricOne might define electricity as the separation of positive and negative electriccharge.charge.

In a simple way electricity is movemet of electrons of a conductor.In a simple way electricity is movemet of electrons of a conductor.

When the charges are separated and stationary we call this static electricity.When the charges are separated and stationary we call this static electricity.The charging of a capacitor is an example.The charging of a capacitor is an example.

The separation of charge between clouds and the earth before a lighteningThe separation of charge between clouds and the earth before a lighteningdischarge is a static electricity.discharge is a static electricity.

WhenWhen thethe chargescharges areare inin motionmotion wewe havehave variablevariable electricityelectricity..


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How is Electricity Produced?How is Electricity Produced?

Friction:Friction: static electricity from rubbing or walking across astatic electricity from rubbing or walking across acarpet.carpet.

Pressure:Pressure: piezo electricity from squeezing crystals togetherpiezo electricity from squeezing crystals together(quartz watch)(quartz watch)

Heat:Heat: voltage produced at junction of dissimilar metalsvoltage produced at junction of dissimilar metals(thermocouple)(thermocouple)

Light:Light: voltage produced from light striking photocell (solarvoltage produced from light striking photocell (solarpower)power)

Chemical:Chemical: voltage produced from chemical reaction (wet orvoltage produced from chemical reaction (wet ordry cell battery)dry cell battery)

Magnetism:Magnetism: voltage produced using electromotive inductionvoltage produced using electromotive induction(AC or DC generator).(AC or DC generator).


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The AtomElectronics starts with electrons.Every atom contains one or more electrons. Electrons have a negative charge.The electrons of an atom can exist only within prescribed energybands.Each shell around the nucleus corresponds to a certain energy band

and is separated from adjacent shells by energy gaps, in which noelectrons can exist.


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The atomThe atom

Nucleus : Protons (+) andneutrons

Electrons (-) rotating on

orbits or energy bandswhich are called shells

Valence electrons:Electrons that are in theorbits farther from the

nucleus


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The AtomThe Atom ProtonsProtons

Positively charged particles located at the center, orPositively charged particles located at the center, ornucleus, of each atomnucleus, of each atom

ElectronsElectrons

Small very light particles with a negative electrical chargeSmall very light particles with a negative electrical charge These electrons move in orbit around the nucleus of anThese electrons move in orbit around the nucleus of an

atom.atom.

NeutronsNeutrons

Do not have an electrical chargeDo not have an electrical charge These particles add weight to the atomThese particles add weight to the atom

Located at the nucleus of an atomLocated at the nucleus of an atom


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ElectronicsElectronics


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Electronics is the branch of science and technology which makes use of theElectronics is the branch of science and technology which makes use of the

controlled motion of electron through different media. It is the branch ofcontrolled motion of electron through different media. It is the branch oftechnology concerned with the behavior and movement of electrons in atechnology concerned with the behavior and movement of electrons in avacuum, gas, semiconductor, etc.vacuum, gas, semiconductor, etc.

Most electronic devices today use semiMost electronic devices today use semi--conductor components to performconductor components to performelectron control.electron control.

An important concept in electronics is PN junction which is formed when twoAn important concept in electronics is PN junction which is formed when twodifferent types of semidifferent types of semi--conductive materials are joined together.conductive materials are joined together.

An electronic component is any physical entity in an electronic system used toAn electronic component is any physical entity in an electronic system used toaffect the electrons or their associated fields in a desired manner consistentaffect the electrons or their associated fields in a desired manner consistentwith the intended function of the electronic system.with the intended function of the electronic system.

Some common electronic components are capacitors, inductors, resistors,Some common electronic components are capacitors, inductors, resistors,diodes, transistors etc.diodes, transistors etc.

Components are generally intended to be connected together, usually by beingComponents are generally intended to be connected together, usually by beingsoldered to a printed circuit board (PCB), to create an electronic circuit with asoldered to a printed circuit board (PCB), to create an electronic circuit with aparticular function (for example an amplifier, radio receiver or oscillator).particular function (for example an amplifier, radio receiver or oscillator).


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Difference between Electricity and ElectronicsDifference between Electricity and Electronics

Electronics refers to theElectronics refers to the controlled motion of electrons in vacuum,controlled motion of electrons in vacuum,gas orgas or through nonmetal conductors (mainly semiconductors),through nonmetal conductors (mainly semiconductors),whereas electrical refers to the flow of charge through metalwhereas electrical refers to the flow of charge through metalconductors.conductors.

Electronics is distinct from electrical, which deals with theElectronics is distinct from electrical, which deals with the

generation, distribution, control and application of electricalgeneration, distribution, control and application of electricalpower.power.


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A conductor is a material that can easilyconduct electrical current.

Most metals have electrons that can detachfrom their atoms and move around. These arecalled free electrons.

The best conductors are single elementmaterial such as Gold, silver, copper,aluminum, iron, etc.,

All above have free electrons and are thereforegood conductors of electricity.

An element with 1, 2, or 3 valance electrons is agood conductor of electricity

Conductors


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Elements with less than 4 Electrons in their

outer rings make good conductors1 32

Because the Electrons are easily dislodged from their orbitand pushed to the atom next to them. (Electron flow)


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An insulator is a material that does not conduct

electrical current under normal condition. In many materials, the electrons are tightly bound tothe atoms. Due to the electrical attraction of theelectrons and protons it is very difficult to get the

electrons to move. Since the electrons don't move, thesematerials cannot conduct electricity. These material have 5 or more electrons on thevalance ring.

Most good insulators are compounds rather thansingle-element material.Wood, glass, plastic, ceramic,air, cotton etc. are good example of insulators..

Insulators


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Elements with More than 4 Electrons in their outer

rings make good insulators5 7

Because the Electrons remain in the outer ringswhen electromotive force ( Voltage) is present.


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SemiSemi--conductorsconductors

A semiA semi--conductor is a material that is between conductorconductor is a material that is between conductorand insulator.and insulator.

An insulator in its pure state is neither a good conductorAn insulator in its pure state is neither a good conductornor a good insulator.nor a good insulator.

AnAn element with 4 valanceelement with 4 valance electronselectrons

Used to manufacture diodes and transistorsUsed to manufacture diodes and transistors

Most common singleMost common single--element semiconductors are Silicone,element semiconductors are Silicone,Germanium and Carbon.Germanium and Carbon.

Compound semiCompound semi--conductors such as Gallium Arsenide andconductors such as Gallium Arsenide andSilicon carbide areSilicon carbide are also commonly used.also commonly used.


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SemiSemi--conductorsconductors

siliconsilicon GermaniumGermanium


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Electronic symbolsElectronic symbols


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ResistorResistor

Fixed Vari

le


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GroundGround

Earth Chassi


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CapacitorCapacitor

Fixed Variabl


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InductorInductor

Air Iron Variab


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DiodeDiode

General

Pur oseZener Light

Emitting


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TransistorTransistor

NPN PNP FET


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Integrated circuitIntegrated circuit

2

3

4

5

13

12

11

10

7 8

1 14

6 9


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SpecialSpecial

V

A

Battery SpeakerVoltmeter

Ampmeter

AntennaFuse


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Reading Resistor Color CodesReading Resistor Color Codes

1.1. Turn resistor so gold, silver band, or space is at rightTurn resistor so gold, silver band, or space is at right

2.2. Note the color of the two left hand color bandsNote the color of the two left hand color bands

3.3. The left most band is the left hand value digitThe left most band is the left hand value digit

4.4. The next band to the right is the second value digitThe next band to the right is the second value digit

5.5. Note the color of the third band from the left, this isNote the color of the third band from the left, this isthe multiplierthe multiplier

6.6. Multiply the 2 value digits by the multiplierMultiply the 2 value digits by the multiplier


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Reading Resistor Color CodesReading Resistor Color Codes


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Resistors in Circuits

Resistors in CircuitsSeriesSeries

Looking at theLooking at thecurrent path, if therecurrent path, if there

is only one path, theis only one path, thecomponents are incomponents are inseries.series.


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Resistors in CircuitsResistors in CircuitsSeriesSeries

nE RRRR ! 21


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R

esistors in CircuitsR

esistors in CircuitsParallelParallel

If there is more thanIf there is more than

one way for theone way for thecurrent to completecurrent to completeits path, the circuit isits path, the circuit isa parallel circuit.a parallel circuit.


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R


esistors in CircuitsParallelParallel

n

111

1

21

21

21

!

!


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R


esistors in CircuitsMixedMixed

If the path for theIf the path for thecurrent in a portion ofcurrent in a portion ofthe circuit is a singlethe circuit is a singlepath, and in anotherpath, and in anotherportion of the circuit hasportion of the circuit hasmultiple routes, themultiple routes, the

circuit is a mix of seriescircuit is a mix of seriesand parallel.and parallel.

Serie

s

Series

Parallel


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pnpn junctionjunction


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The semiThe semi--conductor phenomenaconductor phenomena

Atoms in a metal allow a sea of electrons that are relatively freeAtoms in a metal allow a sea of electrons that are relatively freeto move about.to move about.

Semiconducting materials like Silicon Germanium and carbonSemiconducting materials like Silicon Germanium and carbonhave four valence electrons.have four valence electrons.

Each atom is surrounded by four atoms, as such each central atomEach atom is surrounded by four atoms, as such each central atom

has eight electrons instead of four in its outermost orbit.has eight electrons instead of four in its outermost orbit. This binding force which do not allow the electron to leave theThis binding force which do not allow the electron to leave the

orbit is known as covalent bond.orbit is known as covalent bond.

Due to covalent bond no free electron is available for the flow ofDue to covalent bond no free electron is available for the flow ofelectric current,.electric current,.

Thus a crystal of Silicon or Germanium or carbon in its pure formThus a crystal of Silicon or Germanium or carbon in its pure formbehaves as an insulator at zerobehaves as an insulator at zero kelvinkelvin temp.temp.

At ordinary temp. the electrons have a kinetic motion due toAt ordinary temp. the electrons have a kinetic motion due tokinetic energy.kinetic energy.


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Due to kinetic energy electrons break their covalent bond and get freeDue to kinetic energy electrons break their covalent bond and get freeand leave behind a vacancy for an electron , which called a holeand leave behind a vacancy for an electron , which called a hole

Whenever a covalent bond breaks it creates an electronWhenever a covalent bond breaks it creates an electron--hole pair.hole pair. In addition to electron the electric current also flow due to holes.In addition to electron the electric current also flow due to holes.

Whenever electron from certain location moves to fill a hole, a hole isWhenever electron from certain location moves to fill a hole, a hole iscreated at that particular location.created at that particular location.

In this way electrons begin to move from one place to other , whichIn this way electrons begin to move from one place to other , which

becomes a means for the flow of the current.becomes a means for the flow of the current. Thus at ordinary temperature a crystal of Silicon or Germanium becomesThus at ordinary temperature a crystal of Silicon or Germanium becomes

a semia semi--conductor due to presence of free electrons and holes.conductor due to presence of free electrons and holes.

It is a semiIt is a semi--conductor because the number of free electrons and holes areconductor because the number of free electrons and holes aremuch smaller as compared to the conductor.much smaller as compared to the conductor.


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NN--type and Ptype and P--type semitype semi--conductorsconductors(electronic device by Floyd)(electronic device by Floyd)

A semiA semi--conductor in its purest form is not a good conductor so it is of littleconductor in its purest form is not a good conductor so it is of littlepractical value.practical value.

SemiSemi--conductive materials do not conduct current well.conductive materials do not conduct current well.

This is because of the limited number of free electrons in the conductionThis is because of the limited number of free electrons in the conductionband and holes in the valence band.band and holes in the valence band.

As such the semiAs such the semi--conductive material must be modified, according to ourconductive material must be modified, according to ourrequirement, by increasing the number of free electrons or holes to increaserequirement, by increasing the number of free electrons or holes to increaseits conductivity and make it useful in electronic device.its conductivity and make it useful in electronic device.

This is done by adding impurities to the pure material.This is done by adding impurities to the pure material.

This process of addition of impurities in pure semiThis process of addition of impurities in pure semi--conductive materials isconductive materials iscalled dopingcalled doping

This impurity is usually in the ratio of 1: 10 8This impurity is usually in the ratio of 1: 10 8

Impurities added to semiconductor material can either add free electrons orImpurities added to semiconductor material can either add free electrons orcreate a holecreate a hole

Two types impure semiTwo types impure semi--conductive materials nconductive materials n--type and ptype and p--type are addedtype are added

for the purpose.for the purpose.


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NN--type semitype semi--conductorconductor

To increase the number of conductionTo increase the number of conduction--band electrons in pure silicon,band electrons in pure silicon,

pentavalent impurities atoms are added.pentavalent impurities atoms are added.

These atoms are arsenic, phosphorus , bismuth and antimony.These atoms are arsenic, phosphorus , bismuth and antimony.

Each pentavalent atom forms covalent bond with four Silicon atomsEach pentavalent atom forms covalent bond with four Silicon atomsleaving one extra electron.leaving one extra electron.

This extra electron becomes conduction electron because it is notThis extra electron becomes conduction electron because it is notattached with any atom.attached with any atom.

Because theBecause the pentavalentpentavalent atom gives up an electron, it is often called aatom gives up an electron, it is often called adonerdoner atom.atom.

Silicon or Germanium doped with pentavalent atoms is an nSilicon or Germanium doped with pentavalent atoms is an n--typetypesemiconductor .semiconductor .

N stands for the negative charge on an electron.N stands for the negative charge on an electron.


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PP--type semitype semi--conductorconductor

To increase the number of holes electrons in pure silicon, triTo increase the number of holes electrons in pure silicon, tri--valentvalent impurities atoms are added.impurities atoms are added.

These atoms are boron, indium and gallium.These atoms are boron, indium and gallium.

Each trivalent atom forms coEach trivalent atom forms co--valentvalent bond with four Siliconbond with four Silicon

atoms leaving one extra hole.atoms leaving one extra hole. Holes can be thought of as positive charges because theHoles can be thought of as positive charges because the

absence of an electron leaves a net positive charge on the atom.absence of an electron leaves a net positive charge on the atom.

Because the trivalent atom can take an electron, it is oftenBecause the trivalent atom can take an electron, it is often

called an acceptor atom.called an acceptor atom. Silicon or Germanium doped with trivalent atoms is an pSilicon or Germanium doped with trivalent atoms is an p--typetype

semiconductor .semiconductor .

P stands for the positive charge on an electron.P stands for the positive charge on an electron.


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One side of the bar is doped with negative material (excess electrons or n typeOne side of the bar is doped with negative material (excess electrons or n typeatoms). The cathode.atoms). The cathode.

The other side is doped with positive material (excess holes or p type atoms). TheThe other side is doped with positive material (excess holes or p type atoms). Theanodeanode

n type region has more free electrons whereas p types has more holes as currentn type region has more free electrons whereas p types has more holes as currentcarriers.carriers.

In between is a no mans land called the In between is a no mans land called the pnpn Junction. Junction.

Before the formation ofBefore the formation of pnpn junction, the material is neutral in terms of charge.junction, the material is neutral in terms of charge.

PnPn junctionjunction


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Barrier potentialBarrier potential Just after the formation of Just after the formation of pnpn junction some of the electrons of n typejunction some of the electrons of n type

region cross the junction and enter into the p region where the holes are inregion cross the junction and enter into the p region where the holes are inabundance, thereby filling the vacant site and becomes a part of the impurityabundance, thereby filling the vacant site and becomes a part of the impurityatom.atom.

The impurity atom , with its three valence electrons was a neutral atom,The impurity atom , with its three valence electrons was a neutral atom,becomes a negatively charged atom.becomes a negatively charged atom.

As more and more electrons enter into the p region from the n region aAs more and more electrons enter into the p region from the n region alayer of negative ions is formed in the p region.layer of negative ions is formed in the p region.

As the electrons in the n region leave, this converts the impurity into anAs the electrons in the n region leave, this converts the impurity into animmobile positive ion and a layer of positive, adjacent to the junction isimmobile positive ion and a layer of positive, adjacent to the junction isformed in the n regionformed in the n region

These two layers of positive and negative charges form the depletion regionThese two layers of positive and negative charges form the depletion region

T

his depleted region is formed quickly and is very thin as compared to nT

his depleted region is formed quickly and is very thin as compared to nand p regions.and p regions.

The potential difference across the depletion region is called the barrierThe potential difference across the depletion region is called the barrierpotential.potential.


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The diodeThe diode

When p and n region ofWhen p and n region of pnpn junctionjunctionare connected to metallic wires andare connected to metallic wires andenclosed in a glass or a metallic case thenenclosed in a glass or a metallic case then

such a an encapsulated psuch a an encapsulated p--n junction isn junction iscalled a Diode.called a Diode.


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Biasing a diode.Biasing a diode.

Generally use of a dc voltage to establishGenerally use of a dc voltage to establishcertain operating condition in a diode iscertain operating condition in a diode iscalled biasing of diode.called biasing of diode.

There are two bias conditionThere are two bias condition

ii) forward bias) forward bias

ii) reverse biasii) reverse bias


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The DiodeThe DiodeForward biasForward bias

Applying a positive voltage to the anode and a negativeApplying a positive voltage to the anode and a negativevoltage to the cathode.voltage to the cathode.

The electrons are forced to the junction.The electrons are forced to the junction.

This diode is forward biased meaning current will flow.This diode is forward biased meaning current will flow.


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The DiodeThe Diode

Reverse biasReverse bias

Applying a negative voltage to the anode and positiveApplying a negative voltage to the anode and positive

voltage to the cathode.voltage to the cathode. The electrons are attracted away from the junction.The electrons are attracted away from the junction.

This diode is reverse biased meaning no current willThis diode is reverse biased meaning no current willflow.flow.


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T

he DiodeT

he Diodewith AC Currentwith AC Current If AC is applied to a diode:If AC is applied to a diode:

During one half of the cycle the diode is forward biased andDuring one half of the cycle the diode is forward biased and

current flows.current flows. During the other half of the cycle, the diode is reversed biasedDuring the other half of the cycle, the diode is reversed biased

and current stops.and current stops.

This is the process of rectification, allowingThis is the process of rectification, allowingcurrent to flow in only one direction.current to flow in only one direction.

This is used to convert AC into pulsating DC.This is used to convert AC into pulsating DC.


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The Light Emitting DiodeThe Light Emitting Diode

In normal diodes, when electrons combine withIn normal diodes, when electrons combine withholes current flows and heat is produced.holes current flows and heat is produced.

With some materials, when electrons combine withWith some materials, when electrons combine with

holes, photons of light are emitted, this forms anholes, photons of light are emitted, this forms anLED.LED.

LEDs are generally used as indicators though theyLEDs are generally used as indicators though theyhave the same properties as a regular diode.have the same properties as a regular diode.


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The TransistorThe Transistor

base

collector

emitter


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The TransistorThe Transistor There are two basic types ofThere are two basic types of

transistors depending of thetransistors depending of thearrangement of the material.arrangement of the material.

PNPPNP

NPNNPN

An easy phrase to help rememberAn easy phrase to help rememberthe appropriate symbol is to lookthe appropriate symbol is to lookat the arrow.at the arrow.

PNPPNP pointing in proudly.pointing in proudly.

NPNNPN not pointing in.not pointing in.

The only operational difference isThe only operational difference isthe source polarity.the source polarity.

Early transistors were made fromEarly transistors were made fromgermaniumgermanium but most modernbut most modernBJTs are made fromBJTs are made from siliconsilicon

The basic transistor circuitsThe basic transistor circuits SwitchSwitch

AmplifierAmplifier

PNP

NPN


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The NPN TransistorThe NPN Transistor

N P N

coll ctor mitter

b

se

e -e -

reverse bi s

non-conducting

NPN is one of the two types of bipolar transistors,consisting of a layer of P-doped semiconductor (the "base")

between two N-doped layers. An NPN transistor can beconsidered as two diodes with a shared anode.


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The PNP TransistorThe PNP TransistorPNP, consisting of a layer of N- doped semiconductor

between two layers of P-doped material. An PNP

transistor can be considered as two diodes with a

shared cathode.

VideoVideo


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Integrated circuitIntegrated circuit InIn electronicselectronics, an integrated circuit (also known as IC, chip, or, an integrated circuit (also known as IC, chip, or

microchip) is a miniaturizedmicrochip) is a miniaturized electronic circuitelectronic circuit (consisting mainly(consisting mainlyofofsemiconductor devicessemiconductor devices, as well as, as well as passive componentspassive components) that has) that hasbeen manufactured in the surface of a thinbeen manufactured in the surface of a thin substratesubstrate ofofsemiconductorsemiconductor material.material.

Integrated circuits are used in almost all electronic equipment inIntegrated circuits are used in almost all electronic equipment inuse today and have revolutionized the world of electronics.use today and have revolutionized the world of electronics.ComputersComputers,, cellular phonescellular phones, and other, and other digitaldigital appliancesappliances are noware nowinextricable parts of the structure of modern societies, madeinextricable parts of the structure of modern societies, madepossible by the low cost of production of integrated circuits.possible by the low cost of production of integrated circuits.


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Active and passive componentsActive and passive components

A passive component either a component that consumesA passive component either a component that consumes(but does not produce) energy, or a component that is(but does not produce) energy, or a component that isincapable ofincapable ofpower gainpower gain. Under. Under this methodologythis methodology resistorsresistors,,tunnel diodestunnel diodes,, glow tubesglow tubes,, capacitorscapacitors,, metamaterialsmetamaterials andand

other dissipative and energyother dissipative and energy--neutral components areneutral components areconsidered passive.considered passive.

A component that is not passive is called an activeA component that is not passive is called an activecomponent .Under this methodology, voltage and currentcomponent .Under this methodology, voltage and currentsources and transistors, diodes are considered activesources and transistors, diodes are considered active

components.components.

Lecture 1 Electronics

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