ELECTRONIC DEVICES AND CIRCUITS B.Tech IIIsemester (Common .
LECTURE NOTESONELECTRONIC DEVICES AND CIRCUITSB.Tech IIIsemester(Common for ECE/EEE)Dr. P.Ashok Babu, ProfessorMr. V R Seshagiri Rao, ProfessorMr. K.Sudhakar Reddy, AssosciateProfessorMr. B.Naresh, AssosciateProfessorELECTRONICS AND COMMUNICATION ENGINEERINGINSTITUTE OF AERONAUTICAL ENGINEERING(Autonomous)DUNDIGAL, HYDERABAD - 500043
ELECTRONIC DEVICES AND CIRCUITSIII Semester: ECECourse CodeCategoryAEC001FoundationHours / WeekLTP31-CreditsC4Maximum MarksCIASEE Total3070100Contact Classes: 45Tutorial Classes: 15Practical Classes: NilTotal Classes: 60OBJECTIVES:The course should enable the students to:1. Be acquainted with electrical characteristics of ideal and practical diodes under forward and reversebias to analyze and design diode application circuits such as rectifiers and voltage regulators.2. Utilize operational principles of bipolar junction transistors and field effect transistors to deriveappropriate small-signal models and use them for the analysis of basic amplifier circuits.3. Perform DC analysis (algebraically and graphically using current voltage curves with superimposed load line) and design of CB,CE and CC transistor circuits.4. IV. Compare and contrast different biasing and compensation techniquesUNIT-ISEMICONDUCTOR DIODESClasses: 08PN Junction Diode : Theory of PN diode, energy band diagram of PN diode, PN junction as a diode,operation and V-I characteristics , static and dynamic resistances, diode equivalent circuits, diffusionand transition capacitance, diode current equation, temperature dependence of V-I characteristics,Zener diode characteristics ,break down mechanisms in semiconductor diodes, Zener diode as avoltageregulator.UNIT-IISPECIAL PURPOSE ELECTRONIC DEVICES AND RECTIFIERSClasses: 10Special purpose electronic devices: principles of operation and characteristics of silicon controlledrectifier, tunnel diode, varactor diode, photodiode; Half wave rectifier, full wave rectifier, general filterconsideration, harmonic components in a rectifier circuit , Inductor Filter, capacitor filter, L-Sectionfilter, multiple L-C section, RC filter, comparison of filters.UNIT-III TRANSISTORSClasses: 08Bipolar Junction Transistors: Construction of BJT, operation of BJT, minority carrier distributions andcurrent components, configurations, characteristics, BJT specifications; Applications: Amplifier,switch.Field Effect Transistors: Types of FET, FET construction, symbol, principle of operation, V-Icharacteristics, FET parameters, FET as voltage variable resistor, comparison of BJT and FET;MOSFET construction and operation; Uni-Junction Transistor: Symbol, principle of operation,characteristics, applications (UJT as relaxation oscillator).UNIT-IVBIASING AND COMPENSATION TECHNIQUESClasses: 10Need for biasing, BJT operating point, The DC and AC load lines, types of biasing circuits, biasstability, stabilization factors, stabilization against variations in VBE and β; Bias compensationtechniques, thermal runaway, thermal stability, biasing the FET and MOSFET.
UNIT-VClasses: 09BJT AND FET AMPLIFIERSBJT small signal analysis, BJT hybrid model, determination ofcharacteristics, transistor amplifiers analysis using h- parameters; Fcommon source amplifier, FET as common drain amplifier, FEgeneralized FET amplifier .h-parameters from transistorET small signal model, FET asT as common gate amplifier,Text Books:nd1. J. Millman, C.C.Halkias, “Millman‘s Integrated Electronics”, Tata McGraw-Hill, 2 Edition, 2001.2. J. Millman, C.C.Halkias, Satyabrata Jit, ―Millman‘s Electronic Devices and Circuits‖, TataMcGrawHill, 2ndEdition, 1998.th3. David A. Bell, ―Electronic Devices and Circuits‖, Oxford University Press ,5 Edition,2008.Reference Books:st1. Sedha.R.S, “A Text Book of Applied Electronics‖, Sultan Chand Publishers”,1 Edition, 20082. R L. Boylestad, Louis Nashelsky, “Electronic Devices and Circuits‖, PEI/PHI”, 9thedition,2006.Gupta.J.B,nd3. “Electron Devices and Circuits‖, S.K.Kataria & Sons”, 2Edition,2012. Salivahanan, N. SureshKumar,A. Vallavaraj.Web etails/ElectronicDevicesCircuits -electron-devices-by.htmlE-Text And-Circuits(EDC)-by- J-B-Gupta-full-book-pdf
1UNIT 1PN JUNCTION DIODEINTRODUCTONBased on the electrical conductivity all the materials in nature are classified as insulators, semiconductors,and conductors.Insulator: An insulator is a material that offers a very low level (or negligible) of conductivity whenvoltage is applied. Eg: Paper, Mica, glass, quartz. Typical resistivity level of an insulator is of the order of1010 to 1012 Ω-cm. The energy band structure of an insulator is shown in the fig.1.1. Band structure of amaterial defines the band of energy levels that an electron can occupy. Valance band is the range ofelectron energy where the electron remain bended too the atom and do not contribute to the electriccurrent. Conduction bend is the range of electron energies higher than valance band where electrons arefree to accelerate under the influence of external voltage source resulting in the flow of charge.The energy band between the valance band and conduction band is called as forbidden band gap.It is the energy required by an electron to move from balance band to conduction band i.e. the energyrequired for a valance electron to become a free electron.1 eV 1.6 x 10-19 JFor an insulator, as shown in the fig.1.1 there is a large forbidden band gap of greater than 5Ev. Becauseof this large gap there a very few electrons in the CB and hence the conductivity of insulator is poor. Evenan increase in temperature or applied electric field is insufficient to transfer electrons from VB to CB.
2CBCBoForbidden bandgap Eo 6eVEo 6eVVBVBVBInsulatorCBSemiconductorConductorFiG:1.1 Energy band diagrams insulator, semiconductor and conductorConductors: A conductor is a material which supports a generous flow of charge when a voltageis applied across its terminals. i.e. it has very high conductivity. Eg: Copper, Aluminum, Silver,Gold. The resistivity of a conductor is in the order of 10-4 and 10-6 Ω-cm. The Valance andconduction bands overlap (fig1.1) and there is no energy gap for the electrons to move fromvalance band to conduction band. This implies that there are free electrons in CB even atabsolute zero temperature (0K). Therefore at room temperature when electric field is appliedlarge current flows through the conductor.Semiconductor: A semiconductor is a material that has its conductivity somewhere between theinsulator and conductor. The resistivity level is in the range of 10 and 104 Ω-cm. Two of the mostcommonly used are Silicon (Si 14 atomic no.) and germanium (Ge 32 atomic no.). Both have 4valance electrons. The forbidden band gap is in the order of 1eV. For eg., the band gap energyfor Si, Ge and GaAs is 1.21, 0.785 and 1.42 eV, respectively at absolute zero temperature (0K).At 0K and at low temperatures, the valance band electrons do not have sufficient energy to movefrom V to CB. Thus semiconductors act a insulators at 0K. as the temperature increases, a largenumber of valance electrons acquire sufficient energy to leave the VB, cross the forbiddenbandgap and reach CB. These are now free electrons as they can move freely under the influenceof electric field. At room temperature there are sufficient electrons in the CB and hence thesemiconductor is capable of conducting some current at roomtemperature.Inversely related to the conductivity of a material is its resistance to the flow of charge orcurrent. Typical resistivity values for various materials’ are given as follows.
3InsulatorSemiconductorConductor10-6 Ω-cm (Cu)50Ω-cm (Ge)1012Ω-cm(mica)50x103 Ω-cm (Si)Typical resistivity valuesSemiconductorTypesA pure form of semiconductors is called as intrinsic semiconductor. Conduction in intrinsic sc iseither due to thermal excitation or crystal defects. Si and Ge are the two most important semiconductorsused. Other examples include Gallium arsenide GaAs, Indium Antimonide (InSb) etc.Let us consider the structure of Si.A Si atomic no. is 14 and it has 4 valance electrons. These 4electrons are shared by four neighboring atoms in the crystal structure by means of covalent bond. Fig.1.2a shows the crystal structure of Si at absolute zero temperature (0K). Hence a pure SC acts has poorconductivity (due to lack of free electrons) at low or absolute zero temperature.Covalent bondValence electronFig. 1.2a crystal structure of Si at 0K
4At room temperature some of the covalent bonds break up to thermal energy as shown infig 1.2b. The valance electrons that jump into conduction band are called as free electrons thatare available forconduction.Free electronValance electronholeFig. 1.2b crystal structure of Si at roomtemperature0KThe absence of electrons in covalent bond is represented by a small circle usuallyreferred to as hole which is of positive charge. Even a hole serves as carrier of electricity in amanner similar to that of freeelectron.The mechanism by which a hole contributes to conductivity is explained as follows:When a bond is in complete so that a hole exists, it is relatively easy for a valanceelectron in the neighboring atom to leave its covalent bond to fill this hole. An electron movingfrom a bond to fill a hole moves in a direction opposite to that of the electron. This hole, in itsnew position may now be filled by an electron from another covalent bond and the hole willcorrespondingly move one more step in the direction opposite to the motion of electron. Here wehave a mechanism for conduction of electricity which does not involve free electrons. Thisphenomenon is illustrated infig1.3
5Electron movementHole movementFig. 1.3aFig. 1.3bFig. 1.3c
6Fig 1.3a show that there is a hole at ion 6.Imagine that an electron from ion 5 moves intothe hole at ion 6 so that the configuration of 1.3b results. If we compare both fig1.3a &fig 1.3b, itappears as if the hole has moved towards the left from ion6 to ion 5. Further if we compare fig1.3b and fig 1.3c, the hole moves from ion5 to ion 4. This discussion indicates the motion ofhole is in a direction opposite to that of motion of electron. Hence we consider holes as physicalentities whose movement constitutes flow ofcurrent.In a pure semiconductor, the number of holes is equal to the number of free electrons.EXTRINSICSEMICONDUCTOR:Intrinsic semiconductor has very limited applications as they conduct very small amountsof current at room temperature. The current conduction capability of intrinsic semiconductor canbe increased significantly by adding a small amounts impurity to the intrinsic semiconductor. Byadding impurities it becomes impure or extrinsic semiconductor. This process of addingimpurities is called as doping. The amount of impurity added is 1 part in 106 atoms.N type semiconductor: If the added impurity is a pentavalent atom then the resultantsemiconductor is called N-type semiconductor. Examples of pentavalent impurities arePhosphorus, Arsenic, Bismuth, Antimony etc.A pentavalent impurity has five valance electrons. Fig 1.3a shows the crystal structure of Ntype semiconductor material where four out of five valance electrons of the impurityatom(antimony) forms covalent bond with the four intrinsic semiconductor atoms. The fifthelectron is loosely bound to the impurity atom. This loosely bound electron can be easilyFifth valance electron of SBCBEcEdDonor energy levelEvVBFig. 1.3a crystal structure of NtypeSCFig. 1.3bEnergy band diagram of Ntype
7excited from the valance band to the conduction band by the application of electric field orincreasing the thermal energy. The energy required to detach the fifth electron form the impurityatom is very small of the order of 0.01ev for Ge and 0.05 eV for Si.The effect of doping creates a discrete energy level called donor energy level in the forbiddenband gap with energy level Ed slightly less than the conduction band (fig 1.3b). The differencebetween the energy levels of the conducting band and the donor energy level is the energyrequired to free the fifth valance electron (0.01 eV for Ge and 0.05 eV for Si). At roomtemperature almost all the fifth electrons from the donor impurity atom are raised to conductionband and hence the number of electrons in the conduction band increases significantly. Thusevery antimony atom contributes to one conduction electron without creating a hole.In the N-type sc the no. of electrons increases and the no. of holes decreases compared tothose available in an intrinsic sc. The reason for decrease in the no. of holes is that the larger no.of electrons present increases the recombination of electrons with holes. Thus current in N typesc is dominated by electrons which are referred to as majority carriers. Holes are the minoritycarriers in N typescP type semiconductor: If the added impurity is a trivalent atom then the resultant semiconductoris called P-type semiconductor. Examples of trivalent impurities are Boron, Gallium , indium etc.The crystal structure of p type sc is shown in the fig1.3c. The three valance electrons of theimpurity (boon) forms three covalent bonds with the neighboring atoms and a vacancy exists inthe fourth bond giving rise to the holes. The hole is ready to accept an electron from theneighboring atoms. Each trivalent atom contributes to one hole generation and thus introduces alarge no. of holes in the valance band. At the same time the no. electrons are decreased comparedto those available in intrinsic sc because of increased recombination due to creation of additionalholes.holeFig. 1.3c crystal structure of P type sc
8Thus in P type sc , holes are majority carriers and electrons are minority carriers. Sinceeach trivalent impurity atoms are capable accepting an electron, these are called as acceptoratoms. The following fig 1.3d shows the pictorial representation of P type schole (majority carrier)Electron (minority carrier)Acceptor atomsFig. 1.3d crystal structure of P type sc The conductivity of N type sc is greater than that of P type sc as the mobility ofelectron is greater than that ofhole. For the same level of doping in N type sc and P type sc, the conductivity of anNtypesc is around twice that of a P typescCONDUCTIVITY OFSEMICONDUCTOR:In a pure sc, the no. of holes is equal to the no. of electrons. Thermal agitation continue toproduce new electron- hole pairs and the electron hole pairs disappear because of recombination.with each electron hole pair created , two charge carrying particles are formed . One is negativewhich is a free electron with mobility µ n . The other is a positive i.e., hole with mobility µ p . Theelectrons and hole move in opppsitte direction in a an electric field E, but since they are ofopposite sign, the current due to each is in the same direction. Hence the total current density Jwithin the intrinsic sc is given byJ Jn Jp q n µn E q p µp E (n µn p µp)qE σ EWhere n no. of electrons / unit volume i.e., concentration of free electronsP no. of holes / unit volume i.e., concentration of holesE applied electric field strength, V/mq charge of electron or hole I n Coulombs
9Hence, σ is the conductivity of sc which is equal to (n µ n p µp)q. he resistivity of sc isreciprocal of conductivity.Ρ 1/ σIt is evident from the above equation that current density with in a sc is directlyproportional to applied electric field E.For pure sc, n p ni where ni intrinsic concentration. The value of ni is given byni 2 AT3 exp (-EGO/KT)therefore, J ni ( µn µp) qEHence conductivity in intrinsic sc is σi ni ( µn µp) qIntrinsic conductivity increases at the rate of 5% per o C for Ge and 7% per o C for Si.Conductivity in extrinsic sc (N Type and P Type):The conductivity of intrinsic sc is given by σi ni ( µn µp) q (n µn p µp)qFor N type , n pTherefore σ q n µnFor P type ,p nThe energy band diagram of p-n junction under open circuitconditions( Expression for pn junction diode barrier potential. ) It is known that the Fermi level in n-type material lies just below the conduction band while inp-type material, it lies just above the valenceband.When p-n junction is formed, the diffusion starts. The changes get adjusted so as toequalizethe Fermi level in the two parts of p-njunction.This is similar to adjustment of water levels in two tanks of unequal level, when connectedeachother.The changes flow from p to n and n to p side till, the Fermi level on two sides get linedup.In n-type semi conductor , EF is close to conduction band Ecn and it is close to valence bandedge EVP onp-side.So the conduction band edge of n-type semiconductor can‟t be at the same level as that of ptype semiconductor.
10 Hence, as shown, the energy band diagram for p-n junction is where a shift in energy levels E0isindicated.
11
121.0.5 Doide current equation When a forward bias (VA 0) is applied, the potential barrier to diffusion across thejunction isreduced– Minority carriers are “injected” into the quasi-neutral regions Dnp 0, Dpn 0 Minority carriers diffuse in the quasi-neutral regions, recombining with majoritycarriers Solve minority-carrier diffusion equations in quasi-neutral regions to obtain excesscarrier distributionsDnp(x,VA),Dpn(x,VA)
13 – boundaryconditions: p side: Dnp(-xp),Dnp(- ) n side: Dpn(xn),Dpn( )Find minority-carrier current densities in quasi-neutral regionsEvaluate Jn at x -xp&Jpat x xn to obtain total current density JJ (VA ) Jn ( xp ,VA ) J p (xn ,VA )Consider the equilibrium (VA 0) carrier concentrations:Consider the equilibrium (VA 0) carrier concentrations:p siden sidep p 0 ( x p ) N Ann0 (xn ) N Dn2 in p0 ( x p ) NAn2pn0 (xn ) iNDIf low-level injection conditions hold in the quasi-neutral regionswhen VA 0, thenpp ( xp ) NAnn (xn ) ND
14The voltage applied to a pn junction falls mostly across the depletionregion (assuming low-level injection in the quasi-neutral regions).We can draw 2 quasi-Fermi levels in the depletion region:p n ie( Ei FP )/ kTn n ie( FN Ei )/ kTpn n2i e( FN FP )/ kTpn n i2eqV / AkTExcess Carrier Concentrations at –xp, xnp siden sidepp ( xp ) NAnn (xn ) NDn 2 e q V /kTAnp ( xp ) ipn (x n ) iANDq V /kT pen0NA n p0 e q V /kTAA n 2 e q V /kT2 np ( xp ) ni qV / kT eNAA 1 n2 pn (xn ) ie N DqVA / kT 1
15 Excess Carrier Distribution (n side) d 2 p pn pnn dx2 D L2p pp From the minority carrier diffusionequation: We have the following boundary conditions: p (x ) p (e qV /kT 1) p ( ) 0Annnno For simplicity, use a new coordinatesystem:NEW: x’’0x’0 p (x') Ae Then, the solution is of theform:n p (x') Aenx '/ Lp1 A ex'/ Lp1 x'/ Lp2Fromthex boundarycondition:Fromthex xnboundarycondition:Therefore x'/Lp, x' 0 pn (x') pno (eqVA/kT 1)eSimilarly, we can derive n(x'') nppo(e qVA/kT 1)e x''/Ln , x'' 0 A e x'/ Lp2
16Total Current Densityp side:n side:d np (x'')J qDnnJ p qDpdx''d pn (x')dx'J Jn x x J p x xpn q qDnnLnDpp0(e qVAkT 1)e x ''LnqVkTpn0 (eLpA 1)e x' Lp Jn x 0 J p x 0Dp qV kT 1) DnJ qn2 i LN L N (epD n AA Ideal Diode EquationqVAkTI I(e 1)0 DpDn I0 Aqni N pDLn N A L2
17 Diode Saturation Current I0 I0 can vary by orders of magnitude,depending on thesemiconductor material and dopant concentrations: Dp Dn I0 Aqn2i L N LNpDnA In an asymmetrically doped (one-sided) pn junction, thetermassociated with the more heavily doped side is negligible: D
ELECTRONIC DEVICES AND CIRCUITS B.Tech IIIsemester (Common for ECE/EEE) Dr. P.Ashok Babu, Professor V R Seshagiri Rao, Professor K.Sudhakar Reddy, AssosciateProfessor ELECTRONICS AND COMMUNICATION ENGINEERING INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) DUNDIGAL, HYDERABAD - 500043
Contemporary Electric Circuits, 2nd ed., Prentice-Hall, 2008 Class Notes Ch. 9 Page 1 Strangeway, Petersen, Gassert, and Lokken CHAPTER 9 Series–Parallel Analysis of AC Circuits Chapter Outline 9.1 AC Series Circuits 9.2 AC Parallel Circuits 9.3 AC Series–Parallel Circuits 9.4 Analysis of Multiple-Source AC Circuits Using Superposition 9.1 AC SERIES CIRCUITS
Bowden's Hobby Circuits - Collection of circuits, for everyone. Circuit Exchange International - Andy's website. Good selection of excellent circuits Electronic Tutorials - Collection of electronics tutorials. Dolbowent.Com - Electronic Surplus and Engineering Support. Jordan's Electronics Page - Lots of good circuits here also. LED Webpage.
Microelectronic Devices and Circuits Charles G. Sodini Peter Hagelstein, Judy Hoyt Shawn Kuo, Min Park, Colin Weltin-Wu. Lecture 1 - 6.012 overview February 1, 2005 . - Digital circuits (mainly CMOS) - Analog circuits (BJT and MOS) The interaction of devices and circuits. Title: Microsoft PowerPoint - SP05.Lecture1.ppt
8.3 ELECTRONIC DEVICES AND CIRCUITS LAB 8.3.1 OBJECTIVE AND RELEVANCE The objective of this course is to study various electronic components and design of various electronic circuits like power supply, audio and power amplifiers. This course is considered as fo
Electronic Devices used in Electronic Smoking Systems: Devices commonly known as electronic cigarettes are devices designed to heat electronic liquids or tobacco products as an alternative to smoking aerosol products, which may contain or not contain nicotine, inhaled through the mouth. Page 5 of 15 .
LABORATORY MANUAL CONTENTS This manual is intended for the Second Year students of ECT branches in the subject of Electronic Devices & Circuits. This manual typically contains practical/ Lab Sessions related to Electronic Devices & Circuits covering various aspects related to the subject for enhanced understanding.
1 Introduction to RL and RC Circuits Objective In this exercise, the DC steady state response of simple RL and RC circuits is examined. The transient behavior of RC circuits is also tested. Theory Overview The DC steady state response of RL and RC circuits are essential opposite of each other: that is, once steady state is reached, capacitors behave as open circuits while inductors behave as .
circuits, all the current flows through one path. In parallel circuits, current can flow through two or more paths. Investigations for Chapter 9 In this Investigation, you will compare how two kinds of circuits work by building and observing series and parallel circuits. You will explore an application of these circuits by wiring two switches .
