Chapter 9: Diodes and Diode Circuits. 9.1 Diode Characteristics. Diode Elements. S l i d e. S l i d e. S l i d e

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1 Chaptr 9: Dos an Do Crcuts 9. Do Charactrstcs A o s smpy a pn juncton, but ts appcatons ar xtnsv n ctronc crcuts. Thr mportant charactrstcs of a o ar: Forwar votag rop Forwar Bas, about.7 vots Rvrs votag rop. Dpton ayr wns, usuay th app votag Rvrs brakown votag. Rvrs votag rop that w forc currnt fow an n most cass stroy th o. A o has two as connct to th xtrna crcut. nc a o bhavs ffrnty pnng upon forwar or rvrs bas, t s crtca to b ab to stngush th as. Th ano conncts to th p-typ matra, th catho to th n-typ matra of th o. Do Emnts

2 Ia Dos In an a o, currnt fows fry through th vc whn forwar bas, havng no rsstanc. In an a o, thr wou b no votag rop across t whn forwar bas. A of th sourc votag wou b ropp across crcut rsstors. In an a o, whn rvrs bas, t wou hav nfnt rsstanc, causng zro currnt fow. 5 Practca Dos A practca o os offr som rsstanc to currnt fow whn forwar bas. nc thr s som rsstanc, thr w b som powr sspat whn currnt fows through a forwar bas o. Thrfor, thr s a practca mt to th amount of currnt a o can conuct wthout amag. A rvrs bas o has vry hgh rsstanc. Excssv rvrs bas can caus th o to conuct. 5 Practca Do Forwar Bas 6 6

3 Practca Do Forwar Bas 7 7 Practca Do Forwar Bas 8 8 Rvrs Bas 9 9

4 Rvrs Bas 0 0 Exc Brakown Votag Currnt vrsus Votag In a practca o, thr s vry tt forwar currnt unt th barrr votag s rach. Whn rvrs bas, ony a sma amount of currnt fows as ong as th rvrs votag s ss than th brakown votag of th vc. Currnt Vs Votag Curv for a practca o

5 9. Powr uppy Appcatons Nary a computrs hav som sort of powr suppy. Powr suppy crcuts must: Convrt th ac n votag nto a c votag rqur by th crcut. Ruc th ac votag to a owr vau. Contnuousy ajust th c output votag to kp t constant unr varyng oa contons. Th trm rctfy s us to scrb th convrson of ac nto c. In th crcut shown, ony on-haf of th nput wavform s aow to pass through to th output. Ths s ca haf-wav rctfcaton. Haf-wav Rctfr 5 Crcut Opraton Durng th postv atrnaton, th o s forwar bas an th fu app votag s ropp across th oa rsstor. Durng th ngatv atrnaton, th o s rvrs bas an acts k an opn crcut. No votag s prsnt across th oa rsstor. Th output votag s actuay pusatng c. An appcaton for a haf-wav rctfr s shown on th foowng s. 5

6 Crcut Opraton 6 : rato, about 0 vots rms or. VP Pusatng DC = V P / π, or.8 x V P n ths cas.8 VDC avrag (formua not n txt) 6 7 Fu-wav Rctfr A fu-wav rctfr apps both havs of an ac wavform to th output. Th crcut shown s ca a bphas haf-wav rctfr an somtms a cntr-tapp rctfr crcut. Opraton of a fu-wav rctfr s monstrat n th fgur shown on th foowng s. 7 Fu-wav Rctfr 8 8

7 9 Brg Rctfr A brg rctfr s mor wy us than th cntr-tapp rctfr. Crcut opraton s bst unrstoo by xamnng th currnt paths of th forwar an rvrs bas os urng ach haf-cyc of th nput wavform. 9 0 Ftr Ntworks Most ctronc appcatons rqur smooth c currnt to oprat propry. Ftrng pusatng c crcuts accompshs ths. Ang a capactor to th output of a haf-wav rctfr ftrs th pusatng c nto smooth c. Rpp Fu-wav Rctfr wth Ftr A capactv ftr a to th output of a fu-wav brg rctfr s shown at th rght. On rawback of a hafwav rctfr s th hghr v of rpp votag aftr ftrng. Fu-wav rctfcaton rucs ths rpp votag.

8 Othr Typs of Ftrng mp capactor ftrng s aquat for many ctronc appcatons. In mor crtca appcatons, mor compx ftr ntworks ar rqur to ruc or mnat rpp votag Examps of mor compx ftrs ar: L ftrs. hap of L P ftrs. hap of π En Mscanous Do Appcatons Thr ar many practca appcatons for os byon powr supps. om of ths appcatons ncu: Cppr crcuts that srv to protct crcuts from amag as a rsut of ovr-votag contons. Cpprs ar common n computr crcuts. V R kω 0 V 60 Hz 0Dg Cppr D DIODE_VIRTUAL V 5 V

9 5 V R kω 0 V 60 Hz 0Dg Cppr D DIODE_VIRTUAL V 5 V 5 6 V R kω 0 V 60 Hz 0Dg Combnaton Cppr D DIODE_VIRTUAL V 5 V D DIODE_VIRTUAL V 5 V 6 7 Inustra appcaton of a Cppr Protcton from hgh votag nput Th cppr hr w mt th nput to 5.7 vots 7

10 Mscanous Do Appcatons Isoaton os ar us to soat varous sctons of crcuts from anothr. An xamp of ths s th battry backup for computr mmory. 8 8 Mscanous Do Appcatons Dos can b us to crat an RC crcut that has ffrnt tm constants for charg an scharg. Ths prncp s ca asymmtrca tm constants Mscanous Do Appcatons Dos can aso b us as AM (amptu mouaton) tctor crcuts n rao rcvrs. smuaton n Mutsm Fg09_6.msm 0 En 9.

11 9. pca Dos Thr ar many os that hav spca proprts that ar usfu n ctronc crcuts. A znr o s much k a stanar o n many rspcts, xcpt t s sgn to oprat n th rvrs brakown rgon of ts opratng curv. Fg09-.msm Basc Znr Charactrstcs Znr os ar oprat n thr rvrs brakown mo to prov votag rguaton n a crcut. Th pont whr th rvrs currnt bgns to ncras s ca th kn votag. Th currnt at ths pont s th kn currnt. V ZK I ZK I ZM votag znr kn kn currnt maxmum aowab currnt Znr Votag Rguator crcut Fg09_0(a).msm

12 9.B Varactor Dos Juncton capactanc s prsnt n a rvrs bas os bcaus of th pton rgon. Juncton capactanc s optmz n a varactor o an s us for hgh frquncs an swtchng appcatons. Varactor os ar oftn us for ctronc tunng appcatons n FM raos an tvsons. Thy ar aso ca votag-varab capactanc os. Vaus vary from pf to mor than 000pf. 5 chottky Dos Wh varactor os ar sgn to optmz th ffct of juncton capactanc, chottky os ar sgn to mnmz th juncton capactanc. Juncton s ma of go or aumnum an n typ scon. Ths confguraton mnats capactanc an thrfor gvs thm thr hgh frquncy abty chottky os ar ab to swtch btwn conuctng an nonconuctng stats much fastr than convntona os. Ths fast swtchng sp s th ntfyng charactrstc of a chottky o. Thy ar aso rfrr to as hot-carrr os. 5 6 Currnt Rguator Dos Currnt rguator os ar sgn to prov a ratvy constant forwar currnt ovr a w rang of votags. Th o functons as a constant-currnt sourc. Th forwar rsstanc of a currnt rguator o s vry hgh, from 50 kω to ovr 0 MΩ. Of not s th ong fat porton of th curv. Currnt rmans constant from about -0 vots of nput. 6

13 7 tp-rcovry Dos tp-rcovry os ar charactrz by xtrmy fast swtchng tms. Thy ar prmary us n communcaton crcuts abov GHz. utab for mcrowav us tp-rcovry os ar op ffrnty than othr typs of os, wth ss opng at th pn juncton than away from t. 7 8 Tunn Dos Tunn os ar anothr vc sgn to b oprat at vry hgh frquncs. Th pn juncton s op much mor havy than othr typs of os. Tunn os ar us n th forwar-bas stat an xhbts what s known as ngatv rsstanc. A porton of th charactrstc curv actuay has cras currnt as votag across t ncrass. Your txt has a pctur of ths curv Ths s ca th ngatv rsstanc porton of th curv. Ths contracts ohms aw Imag from Atantc-Mcrowav 8 9 PIN Dos PIN os ar anothr vc ntn for us at xtrm frquncs (00 MHz 00 GHz). A ayr of p-typ matra s sparat from a ayr of n-typ matra by a ayr of ntrnsc or vry ghty op scon. ayrs, s pctur n txt Ths smconuctor sanwch of p-typ,ntrnsc, an n-typ matras gvs ths o ts nam. 9

14 0 PIN Dos Bcaus of th ntrnsc smconuctor matra n btwn th p an n matra th capactanc whn rvrs bas s vry ow. Th MPN0 has ony.pf ovr a w rang of rvrs votags Ths maks t w sut for us at vry hgh frquncs. Th rf rsstanc can vry from ss than on ohm wth a hgh forwar currnt to w ovr on thousan ohms for ssr currnts. Ths maks thm w sut to actng as a currnt contro rsstanc. 0 Parta Data ht for MPN0 En Troubshootng Do Crcuts Bcaus os ar so common n th ctroncs nustry, t s mportant to b ab to troubshoot an rpar systms that mpoy os. Do fcts ncu: Ano-to-catho short. Ano-to-catho opn. Low front-to-back rato. Out-of-toranc paramtrs.

15 Troubshootng Do Crcuts Tsts that can prform on os to chck for thr opraton ar: Votag masurmnts. Ohmmtr tsts. Do tstrs. Rctfr o fcts fa nto on of two casss: Powr suppy s fctv, but no vsb amag an no fuss ar bown. Th rctfr crcut shows amag or a fus s bown.