B YA R U P C H A K R A B O R T YBASIC ELECTRONICSpresentation
Introduction Lattice Super conductor & insulator Semi conductor : intrinsic & extrinsic Band theory of conduction Diode Rectifier Transistor
Lattice In mathematics, especially in geometry and grouptheory, a lattice in R^n is a discrete subgroup ofR^n which spans the real vector space R^n . Every lattice in R^n can be generated from a basisfor the vector space by forming all linearcombinations with integer coefficients. A lattice may be viewed as a regular tiling of a spaceby a primitive cell. Lattices have many significant applications in puremathematics, particularly in connection to Liealgebras, number theory and group theory.
Lattice Energy The lattice energy of an ionic solid is a measure ofthe strength of bonds in that ionic compound. It is usually defined as the enthalpy of formation ofthe ionic compound from gaseous ions and as such isinvariably exothermic. In the case of NaCl, the lattice energy is the energyreleased by the reactionNa+ (g) + Cl− (g) → NaCl (s) which would amount to-787 kJ/mol.
Superconductor & Insulator Superconductivity is a phenomenon of exactly zeroelectrical resistance and expulsion of magnetic fieldsoccurring in certain materials when cooled below acharacteristic critical temperature. An electrical insulator is a material whose internalelectric charges do not flow freely, and which thereforedoes not conduct an electric current, under the influenceof an electric field. A perfect insulator does not exist, but some materialssuch as glass, paper and Teflon, which have highresistivity, are very good electrical insulators.
Semiconductor Semiconductors are of two types- Intrinsic Extrinsic
Intrinsic Semiconductor An intrinsic semiconductor, also called anundoped semiconductor or i-typesemiconductor, is a pure semiconductor withoutany significant dopant species present. The number of charge carriers is thereforedetermined by the properties of the material itselfinstead of the amount of impurities. In intrinsic semiconductors the number of excitedelectrons and the number of holes are equal: n = p.
Band Theory of conductionsuperconductorsemiconductorinsulatorConductionBandConductionBandConductionBandValenceBandValenceBandValenceBand
Free & Bound Electron• Free Electron : Electron that can move freely . Electron without the coulombian attraction force ofnucleus . Bound Electron : Electron that moves round thenucleus . Electron feeling the coulombian attraction forcewith the nucleus .
Extrinsic Semiconductor An extrinsic semiconductor is a semiconductor thathas been doped, that is, into which a doping agent hasbeen introduced, giving it different electrical propertiesthan the intrinsic (pure) semiconductor. Doping involves adding dopant atoms to an intrinsicsemiconductor, which changes the electron and holecarrier concentrations of the semiconductor at thermalequilibrium. Dominant carrier concentrations in an extrinsicsemiconductor classify it as either an n-type or p-typesemiconductor.
Semiconductor Doping Semiconductor doping is the process that changes anintrinsic semiconductor to an extrinsic semiconductor. During doping, impurity atoms are introduced to anintrinsic semiconductor. Impurity atoms are atoms of a different element than theatoms of the intrinsic semiconductor. Impurity atoms act as either donors or acceptors to theintrinsic semiconductor, changing the electron and holeconcentrations of the semiconductor. Impurity atoms are classified as donor or acceptor atomsbased on the effect they have on the intrinsicsemiconductor.
The two types of extrinsic semiconductorN-type semiconductorsP-type semiconductors
N-type semiconductors Extrinsic semiconductors with a larger electronconcentration than hole concentration are known as n-type semiconductors. The phrase n-type comes from the negative charge ofthe electron. In n-type semiconductors, electrons are the majoritycarriers and holes are the minority carriers. N-type semiconductors are created by doping an intrinsicsemiconductor with donor impurities. In an n-type semiconductor, the Fermi energy level isgreater than that of the intrinsic semiconductor and liescloser to the conduction band than the valence band.
P type Semiconductor As opposed to n-type semiconductors, p-typesemiconductors have a larger hole concentration thanelectron concentration. The phrase p-type refers to the positive charge of thehole. In p-type semiconductors, holes are the majority carriersand electrons are the minority carriers. P-type semiconductors are created by doping an intrinsicsemiconductor with acceptor impurities. P-type semiconductors have Fermi energy levels belowthe intrinsic Fermi energy level. The Fermi energy levellies closer to the valence band than the conduction bandin a p-type semiconductor.
Concept of Diode What is a diode?: a diode is such a semi conductordevice which does not follow Ohm’s Law. In electronics, a diode is a two-terminal electroniccomponent with an asymmetric transfercharacteristic, with low (ideally zero) resistance tocurrent flow in one direction, and high (ideallyinfinite) resistance in the other. A semiconductor diode, the most common typetoday, is a crystalline piece of semiconductormaterial with a p-n junction connected to twoelectrical terminals.
Rectifier A rectifier is an electrical device that converts alternatingcurrent (AC), which periodically reverses direction, to directcurrent (DC), which flows in only one direction. The process isknown as rectification. Rectifiers have many uses, but are often found serving ascomponents of DC power supplies and high-voltage directcurrent power transmission systems. The simple process of rectification produces a type of DCcharacterized by pulsating voltages and currents (althoughstill unidirectional). Depending upon the type of end-use, this type of DCcurrent may then be further modified into the type ofrelatively constant voltage DC characteristicallyproduced by such sources as batteries and solar cells.
Half Wave Rectification In half wave rectification of a single-phase supply, eitherthe positive or negative half of the AC wave is passed,while the other half is blocked. Because only one half ofthe input waveform reaches the output, mean voltageis lower. Half-wave rectification requires a single diode in asingle-phase supply, or three in a three-phase supply. Rectifiers yield a unidirectional but pulsating directcurrent; half-wave rectifiers produce far more ripple thanfull-wave rectifiers, and much more filtering is needed toeliminate harmonics of the AC frequency from theoutput.
Full Wave Rectification A full-wave rectifier converts the whole of the inputwaveform to one of constant polarity (positive ornegative) at its output. Full-wave rectification converts both polarities of theinput waveform to DC (direct current), and yields ahigher mean output voltage. Two diodes and a center tapped transformer, or fourdiodes in a bridge configuration and any AC source(including a transformer without center tap), are needed.Single semiconductor diodes, double diodes withcommon cathode or common anode, and four-diodebridges, are manufactured as single components.
Transistor A transistor is a semiconductor device used to amplifyand switch electronic signals and electrical power. It is composed of semiconductor material with at leastthree terminals for connection to an external circuit . A voltage or current applied to one pair of the transistorsterminals changes the current through another pair ofterminals.Because the controlled (output) power can be higherthan the controlling (input) power, a transistor canamplify a signal.//Today, some transistors are packaged individually, butmany more are found embedded in integrated circuits.
About BJT Bipolar transistors are so named because they conduct byusing both majority and minority carriers. The bipolar junction transistor, the first type of transistor tobe mass-produced, is a combination of two junction diodes,and is formed of either a thin layer of p-type semiconductorsandwiched between two n-type semiconductors (an n-p-ntransistor), or a thin layer of n-type semiconductorsandwiched between two p-type semiconductors (a p-n-ptransistor). This construction produces two p-n junctions: a base–emitter junction and a base–collector junction, separated bya thin region of semiconductor known as the base region(two junction diodes wired together without sharing anintervening semiconducting region will not make atransistor).
The CE Characteristics of n-p-n Transistor Circuit: diagram :