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7 = Ihavenin’s _< \nenrem al ‘ ine J. Caleuiode the turret = = Vy Flobsing throug in | LB — hh - 8 Ra 2 \. Det Ot cut Ny Short Cru vo A. +Rs an Rai Ry ees eee Ve = Vag - Ven OA Nea -Vae oe Arn_- Win Ra Oo _ Bt Ra ; a \Lah eExobe ; . . p Bz 8 Colcuicwe the | - ae v —_ WA 1 V>a—— Current Flowing. Bo [Ty ,—1hough Ra Js, eee Bic E — a Ee Tae Vou Ait Ra 7 Ra ths _ _ Une =X, xo Vee eloyRy Nita = Vae = Vee. “OR Vec-Vac Raw Zs Ry tRan oe. Rui rRo By + Ba Ry +Rs __ (calert. Curent FOm Vita = Nag — Vac oR Vee + Vac Ran = Ri xa + Ry eR et S . Ra tks Cateye Cem Tomy Anus | Caters. “he Cavers Rotng Sigua a Re Rew soe Rs Reser NagsNan Le RY Ry +R Ps No ; (Ry Ri) 1 Rs, Vi. = 1. AS Ran a(R, + Ra) k ine ba CRA 4 Ra) 4 R3 Chapter 3 7 Basing the PN-junction to a device or circuit. Bias ie the extornal application of a potential ‘ . al 4 84 a No bias applied to PN junctio wig. act ie iglmtion fa 7] i to ¢ 0 bias was applied. Refer tea'was applied. When the PN-junction is formed n dto the PN-junction when ni a detailed analysis of what happene Hf + wi Ae fh s applied to the PN-junctio : voonbesten " such a way that its positive Forward bias occurs when the extemal voltage source is connected in si vexed to the N-type torminal is connected to the P-type\material and its negative terminal 18 con tential. The effect material. The polarity of extemal sdurce is such that it opposes the barrier po ca i holes inthe of the forward-bias voltage is that the positive side of the external voltage repels repelled P-type material and causes them to drift across the junction. Similarly, the electrons are rep by the negative terminal of the external voltage and they too drift across the Mette Because of this, the potential barrier is reduced and the depletion layer narrowed. Should the as vo! nA be increased to such an extent that it overcomes the barrier potential the depletion layer wou cease to exist. Electrons would now flow freely from the N-type material across the junction to the P-type material and the holes would flow in the opposite direction. Majority carrier current is the result, Increased bias Small forward-bias voltage Barrier potential not yet overcome Barrier potential overcome Fig. 3.21: Tha effects of forward blasing a PN-junction Reverse bias applied to the PN-junction Reverse bias occurs when the extemal voltage source is connected in such a way that its positive terminal is connected to the N-type material and the negative terminal to the P-type material. The polarity of the external source is such that it aids the barrier potential. The effect of the reverse bias voltage is that its positive side attracts the electrons from the N-type material, and its negative side attracts the holes from the P-type material. This causes the potential barrier to increase and the depletion region to widen. No majority carrier current flows.-The only current that flows is due to the minority carriers. An increase in temperature will cause an increase in minority current carriers and thereby increasing the leakage current, known as the reverse saturation current, a P N Increased reverse-bias ts Depletion layer big ‘i Small reverse-biag S88 voltage @! Depletion layer —— small . Fig, 3.22: The effects of reverse blasing a PN junction 4 wy Chapter 3 N-type material If a pentavalent atom, like phosphorous, is added to a pure silicon crystal, the crystal structure below in Fig. 3.11 is formed. Four of the five valence electrons of phosphorous will form covalent bonds with its four neighbouring silicon’ atoms, and the fifth valence electron will be left unbound. This electron is more loosely held in the valence Fig. 3.41: Adcition of a pentavalent atom results in N-type material shell than the four that are — : . - covalently bonded. This electron tends to become a “free” electron and is readily available as a cartier of current. Since pentavalent atoms eventually give up this “free” electron they are known as donor atoms. The process of generating “free” electrons is called donor doping. Since the intrinsic semiconductor has been doped with a controlled amount of pentavalent atoms, there exists many free electrons and since the charge on an ¢lectron_is negative, the type of. material thus formed is called N-type material (where N is for the negative charge of an electron). In N-type material, free edectrors are the major means of conduction and therefore are described as stajority charge carriers. In N-type material, holes are generated by thermal or other means and also act as charge carriers, but they are relatively few when compared to the. electrons. These /e/es in N-type material are known as minority charge carriers. ‘The N-type material is still electrically neutral. No electrons have been lost or gained but they are available for | j conduction ° Ifa trivalent atom, like Boron, is added to a pure silicon crystal, the crystal structure below (Fig. 3.12) is formed. The ¢#ree boron valence electrons will form covalent bonds with three neighbouring silicon atom valence electrons. This leaves the fourth silicon atom valence electron witheut a covalent bond and as a : Electron- result, a vacancy or fiole exists, hole pair These holes tend to attract electrons and. can; ” 1 an be. “fi free electrons, - ! Covalent results in. holes appearing et t vow ~ bond elsewhere. These trivalent atoms are therefore known as acceptor atoms. The process of generating holes is called acceptor doping. When the intrinsic semiconductor is doped with trivalent atoms, the number of holes created far ex i is, the . ar exceeds the number of charge on a hole is positive, this ty, ee ens, Since the pe of material is referred to as P-iype materi TBE 7 I iy erial, Here the mojority charge curriers are the holes and the minority charge carriers are ih Fig. 3.12: Addition of a trivalent atom results in P-type material ¢ electrons. , ee “Types “OF aronsfo1mets_ ; __4Step_down dransfecmer:_| _& Step_UP___unstowner__y © __¢.Centte Aup Atuasporma _ __ylMavnpie _lunding Hunsfirre | Fisovwhon Aur forma ( _y Auto. dransermer, |x Used 40 fot ts used Fos elechical tsolasioo Tr used For AfansmisS20 Purposes sed do de eFine | _Awo different _ OP PUcation ly Used to Supply fferey Seconccry, ang fo dieterent hoads LTO Preveas Narmenics Foe. true erg. - _|Fien one side to Othe Sicle ___ 4 Used to Produc A Natichle AC. | Nottage _‘Taom 1. Fixed Noltage Ac. - SuPRly. lote Wate Rectifier - Fi \ders Adlwaniages Disuiduanigg es EASY do Con ste Const Cc _¥ Genecdes Noumonics _ _}#Requue leborete fHeang fo give a | ¢ Ripple Fac: ts high = Ql PP gt re « USe | Vey Few Components Steucly -D [a Output x The Cost ts Vey “low. | 4 Poor Power Output : Capacdot Filer Aclvantages Disaclwaniqgges x Ost Offative A Vgn \ocds + Ripple_An cease Wun ¥ Geox Sracoining “acaton ar low “Curent eco Culient LOeg Usecl t0- Kigh Motiage | lower Poser Suppiia yBaarse oF Hs ~ Serpe, te Is Also. -xOutpad Velie cays With _icigase “1a Lead a Feene|. ta A high Caneen -——hipple.'s__Unim porting Sup pices bohee ROW Fite” Advanuges Disaduantages. __ + Beater _Lupple _te eduction beRppe. “Ancredse both had Cumen __ diner Suenple_ Copacitor__ howe Outpra Votoge due _to \oltege Fler cop acess the tester a 4 Good Smositing action |x Qykput Notage. 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Biro “Suinchion TWreins isin 4 Bot) A ipoiy —ttansisme 16 a Ame tema CB, Enc | Curren AMPIE Ying devies wn Which Sman in ped Can Conno| de Magne ucle bp A WMech lease Outpu — Curvent Bi poder —>Meons tha Me deie bs meade From Semiconductor Matestat in Which Conducten Vettes on Roh Koes and ie cttons Cra yosey and Mmrokts) Charge Carnes Elemear OF — Tronisigtvss : ad EmmiieR. -> Sappues the Majoseey Castes Woh Arunyisao0s GW) Covlects -> collects Ane Curent Fa Circe OPercies (ay Base > Psovides She unciion gor Paper imteraten beieen Me emmidor ancl Cowectr. OPeicti09 . ss Emmisie —\S OF tow VeSi Shroiey Medesial thay has been heauly Coped with Irvpasthes Base ~The Cental Yegion of dhe Munsistee Gnd ts OF Nigh Kesisdinty _ Co (lector aha Q lowe Tes stiety Maan Nhe emmites and is de arer Vhee the Crarye Carwies ae cotiected. Oferction of a hiunsitay. 5 The emmite loase Junction Former’ biased abou (O,av do o,3¥ Gerraram ond akan Oby 40 Os1y Silica) and Collector bue Junction s-_—pevensed loiasedf Cot SF GYLAQ¥ and fav oe Common. “s A Type oF _ ‘Ttansisiaas Cosries Que elections NPA 5 Trunsisps the M arent ontg On instead OF PHR + Transisiat the Maprity Coaties Oe holes elections: Transistor — Cetrem Te = Emile Curent Ta = Boe Curent Te 2 Cotlecta Giant Transiva Vio tage NPN -> Buse Is Posidie borth lesped Yo the emomter cid he covlector (Is more Pos\tue akan Ah base ; PHP > Bae 's Degaaiue Wirth wesped Ao dhe erm eter and Me Collector ts moe Negatwe dhan the bas, BIT as GQ Switch APP CE Ons @ Re outer w AMPIRe ww Ale ctione switch, Transists Gan opercrie _in_dhsee__ ce gos. a) Cut off fegtoas > tS lthen both buse -egmmiter and base Collector Junction are revened Llased )) Kecrve os linea Weqlon > Base emmiter Jun chea ls Forward loiased and base Collector fegloa s ieverse § biased G) Boduiasoa _fegron, —slwhen both the base emote and base Colector Junchon cue Fomwd — (oiasd, Summerticay — Push Pu Class _AB__am pifier Ww Advantage Disaiwnlsye Bist a Expensive - ALGnSFoI Mery Distortion ts etimneted. Coss - over disiasiion g Gross over cistron —> OCs chung the Pessoc| When One Atansistor beyins fo. Swith OFF and the othe, one Shaeis 40 Gioith On. yOPen-loop An ampiifier wn twhich the Outp IS Noe Monitored OF Fedbact fo Compensatec for Cwreed 06 Load Changes , y Closed Logs ~> An cevpiifie te Monitored and as Signe Ws Fed back 4o dhe Wpat, Comectoe _ Aachen Cun be 4duten, ¥ liypes. OF Feedbact > Positive Feed back am pifier — ‘The Signe Fedbeck Is IN Pnase wrth dhe inPut Bab ->Negaawe Feedback amptifie — The Stgna( Feed back ta antipnase Chad Qut OF Phase) tut the inpud Sana. Block Diagn, fin deropiifer A Wah Feed baci ‘networ B, 4 ME de No ~ ‘a a | VF e+ “The Feaclloock Votiaye Ve is tavcen Fiom the Ourpt Vo ard ts Fed back (n Geiphase Wh the put Vota \k-Th the houy the. lapu Voltage | \n Yeduced Mra WE Improve Perfomane _ of Negative Feedbock % Reducing tks ain aa ¥ Reducing Noitce ‘ Re ducing dicrortion % improving ts Shabi ite] 4 INCRasing Hy Operating oandtuitl, & Increasing the taper tmvpectance cand decteasing She Cutpus Im Peclance, -> Feedback ob taaed, 4 Senes Feedback > When Pow of we Feedback Sana ‘8 Gonnecled in Geates both > the put Sranal x Douad Feedloace > When Ye input and Curpay Sranais are Converted Ko Currents added anc Yeconverted A A Nottage and appiiel 40 the Amp li fier: Eleil efrect Trunasiocs C F ET) “Fret eFFeet ttunsisior > A Semicondudor vessizy the Velue OF Yesisiance beng Condsotled boyy the Potential appred to the Conwol clecrode. “Types oF eT 4 JFET > Junction Fieid effect Hunsister 4 Moser > Metal Oxide Semiconductor tied pret Hensisas othe’ Fiat ts Produced by a Voviuge appied between the Aade electiode and Conducting Channel, > BYT - HE Current OPErcHted > FET tre Nottage Opeteeect_ otis ae clesciwed cs Uatpotar — dtunsisions because Currena le Cue Aimoist entively to tre Flow OF Qhe Ayre OF Caries. * Channel FETs ~> elections €P~ Channel Fe ~» Hotes, Consist sg of A mei age = Comaay | SWicon ctotide Kictecinc, Akd the Conducting Chana ec. > Nlosfei ts Catied tsutoded Gate FE or LGFET > dt Cun be OPpecded Uncla Forward and reverse biase Condinrons inde: Foruced bias ts cated the enhanemens mode -7DeaPletion Mode mosrer Can cdo be oPpercrted bata GQ Posie gore Vorreege since there \s no yewlse lotased PA Junction Gs in the SET UN uaction Tunsi stor Upt sNST +18 QQ Mee Fewsueca| Single Junchon cleuce Whi, Possesses A Negative yesistane Charact ed sc APP carens q Inlioliiag OSCi (ato & Liming Currents € Triggeting dewtes for Murra dh rigpel ON, UST is Used in bistaie mode ~ UjT Offa the acltantage of beiny CxXeend Cuceit Swmpiifies Giitowng the” Vlimineetioq OF G@ Numba OF Componemt NBtDiageams. 4~Chataclenstie OF UST he Higgee ScR. ComMos logue laveter 4Gloss over distortion ¥Block iagrcaen Feedback nettore eon - Com Plemerriaay CiASSB $Symometricea Push Puy CLASS AB ¥ Complementary Symmary PasnPuy B Complementary Sqemety Push Puy KB : “7 _f Pe: RA LAT ONAL __Ampigicrs clonal A er ads hi b “Gein olive Coupte. AMP fey “wide th the e_Ctrpabticty i aenph gag. 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Me. Sate ou which te per INnpud Wtuge 24 drat Inerew |VOrtage Changes OH A Partie —{ + jos Ke: Cc ~d —— ta a Vin aa SS > Nin ia | — AQ >, Vo [ i }-+ - ™ _ / al — r 7 L = = — ae a Vo Nin v| 2 | V. Ko do Ven | SUMMING xlhe Curput Vortwe \s Ye Sum oF Cy the input Vortege Vf Hy np {Vi No Vy af . Vo m ~Y ath : aS te _—4R ve : V3-——foot + Yo Tr ay ferision ave eauey Vo= - Vit Va +¥3 Compare ree Oo the OPeraronal — Aaa Pirfier “without “Feedback es BN eee a Ln bg Negi oe af {4 Lo oe LIE CTR RCA " Thy tto« > Ts a Gea OF semconcucto “‘clevices Which hee ck Fay Suh O07 Cherewserisitc (S CR) Sittcon_Contvolled _Rectigier SK, ~> Vy gq Four layer PeN- Pe Semicondudor device with Mee dermnals Caued Anode Cathode GALE ( ) Rignon y Whe C1 Neyctive —Porentra} Is aPPiect 40 Ahe anecle Wh Fespect to Ake Cohode Ti, 6 belese bits] Gad as a sesutt dhae 6 No CuMeRt Flowing thioyci dhe Ahyristor, The dhyisty then Sai be A fovesse blocting. ylwhen ca Posie Potentiay & appt 40 dhe cinede Wotth “NeSpecy to dhe Cathode dnd no Jae agra Is cepplied «Fe om, Is fawad biased bet MR Qunction IS Yatewe biased. Medhod OF _ Sweidhing = SCR COEF + By Recluciny the Curent to less Shan the holding — Cusrent a By Removing dhe anede Current *By Short Cicuiting and teverse biase {lo clu Cusem = The Mimum Yaue oF dhe Gurren _ Needel Ho beep an Scr om PPPiicottions OF SCR x Rela _Contio | & Modoc Condioy ¥Tide™ delay % MeGter Conric| % Reguiated Powe Sa ppries % Bowery Charges Rhode Sus thes "ot 4 
