Basic Electronics Definitions

8/10/2019 Basic Electronics Definitions

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INTRODUCTION TO ELECTRONICS

Voltage - 1) the electric potential difference bet een t o point! in a circ"it that ill ca"!ean electric c"rrent to flo bet een the!e t o point!# $) the electro%oti&e pre!!"re that

force! electric c"rrent to flo thro"gh a co%plete circ"it# &oltage i! %ea!"red in&olt! C"rrent- 1) the rate of flo of electric charge thro"gh a cond"ctor# $) the net tran!fer ofelectric charge per "nit ti%e# c"rrent i! %ea!"red in a%pere!'1 a%pere ( 1 co"lo%b per!econd)

o er - 1) the rate at hich or* i! done in a circ"it# $) the a%o"nt of energ+ 'in ,o"le!)that a de&ice deli&er! or con!"%e! di&ided b+ the ti%e 'in !econd!) that the de&ice i!operating# ) the prod"ct of the &oltage acro!! an electrical path and the c"rrent thro"gh po er i! %ea!"red inatt!

Circ"it - 1) the co%plete path or clo!ed loop thro"gh hich electric c"rrent flo ! fro% the po er !o"rce to the load'!) 'a load i! a co%ponent or de&ice that con!"%e! po er) andthen bac* to the !o"rce# $) an electrical interconnection of po er !o"rce! and electricalload! that perfor%! a certain electrical or electronic f"nction

Re!i!tance 'R) - 1) the abilit+ of an electronic co%ponent or an electrical path to re!i!t theflo of c"rrent# $)the ratio of the &oltage 'V) acro!! a cond"ctor to the c"rrent 'I)flo ing thro"gh it. i/e/. R ( V0I Capacitance 'C)- the ratio of the charge ' ) !tored in a capacitor to the &oltage 'V) acro!!

the capacitor. i/e/. C ( 0V Ind"ctance - the a%o"nt of electro%oti&e force 'e/%/f/) or &oltage ind"ced ithin a circ"it b+ a change in c"rrent flo ing thro"gh the circ"it Reactance - the abilit+ of a capacitor or ind"ctor to re!i!t the flo of alternating c"rrent I%pedance- the abilit+ of a circ"it to re!i!t the flo of alternating c"rrent

arallel Connection 'refer to 2ig"re 1a) - a circ"it arrange%ent herein the electronicco%ponent! are connected to the po er !o"rce independentl+ of each other# in a parallelconnection. each co%ponent ha! the !a%e &oltage acro!! it 'b"t each %a+ ha&e a differena%o"nt of c"rrent flo ing thro"gh it) Serie! Connection 'refer to 2ig"re 1b) - a circ"it arrange%ent herein the electronicco%ponent! are connected to each other along a !ingle electrical path# in a !erie!connection. there i! onl+ one po!!ible c"rrent path. !o each co%ponent e3perience! the!a%e a%o"nt of c"rrent 'b"t each %a+ ha&e a different &oltage acro!! it)

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2ig"re 1a/ Re!i!tor! inarallel 2ig"re 1b/ Re!i!tor! inSerie! Open Circ"it- a circ"it that ha! a c"t. brea*. or interr"ption. pre&enting c"rrent fro%flo ing thro"gh it# an open circ"it %a+ be d"e to a bro*en or di!connected ire. or ada%aged co%ponent that bloc*! c"rrent flo Short Circ"it - an "n anted or abnor%al lo -re!i!tance path that ca"!e! c"rrent to b+pa!!a co%ponent or load# the lo re!i!tance of a !hort circ"it can ca"!e large a%o"nt! ofc"rrent to flo . hich can re!"lt in greater da%age '!"ch a! an open circ"it d"e tocond"ctor b"rn-o"t)

4ro"nd - 1) the co%%on point of c"rrent ret"rn in a circ"it# $) the point'!) in a circ"it thati! at 5ero &olt# ) the connection of an electrical circ"it to earth# in a circ"it that ha! a!ingle po er !"ppl+. the gro"nd i! generall+ the point to hich the negati&e ter%inal i!connected

a!!i&e Co%ponent! are electronic co%ponent! that %a+ be characteri5ed a! follo !6 1) the+ do not re7"ire a po er !"ppl+ in order to operate#$) the+ do not a%plif+ or ! itch !ignal!#

) their beha&ior or ba!ic electrical characteri!tic! do not change ith the application of!ignal# and8) the+ are often "!ed for !i%ple and ba!ic application! !"ch a! li%iting c"rrent. !toringelectrical charge. filtering. !"ppre!!ing c"rrent !"rge!. ti%ing. and t"ning/ E3a%ple! of pa!!i&e co%ponent! are re!i!tor!. capacitor!. and ind"ctor!/

Co%ponent! that are not pa!!i&e are referred to a!9acti&e co%ponent!9/

Re!i!tor Val"e Color Coding

The color band! on a re!i!tor indicate the re!i!tance &al"e of a re!i!tor/

:! !ho n in 2ig"re 1. a co%%on re!i!tor "!"all+ ha! 8 color band!. the fir!t t o of hichindicate! the fir!t and !econd digit of it! re!i!tance &al"e hile the third band indicate! then"%ber of 5ero! that follo ! the fir!t t o digit!/ The fo"rth band indicate! the error or

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tolerance of the re!i!tor/ 2or e3a%ple. the top re!i!tor in 2ig"re 1 ha! a re!i!tance &al"e of1 *ilo-oh% '1; oh%! 3 1;;) / So%e re!i!tor! ha&e = color band! to indicate theirre!i!tance &al"e! %ore preci!el+. an e3a%ple of hich i! the botto% re!i!tor of 2ig"re1/

2ig"re 1/ The color band! of a re!i!tor indicate it!re!i!tance &al"e '!ee Table 1)

Table 1/ Re!i!tor Color Code! 'Refer to 2ig"re 1)Color 1!t Digit $nd Digit rd Digit ?"ltiplier Tolerance

@lac* ; ; ; 1 -@ro n 1 1 1 1; -Red $ $ $ 1;; -Orange 1A -Bello 8 8 8 1;A -4reen = = = 1;;A -

@l"e 1? -Violet 1;? -4ra+ 1;;? -Fhite G G G 14 -

4old - - - ;/1 =>

Sil&er - - - ;/;1 1;>

No Color - - - - $;>

Cr+!tal O!cillator!

:n o!cillator i! a de&ice that prod"ce! a rec"rring a&efor% or o!cillating !ignal. !"ch a! a

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&oltage that contin"o"!l+ fl"ct"ate! 'o!cillate!) bet een t o le&el!/ O!cillator! aregenerall+ "!ed a! ti%ing or cloc*ing de&ice! in electronic circ"it!/

: cr+!tal o!cillator i! !i%pl+ an o!cillator that9! %ade of a pie5oelectric cr+!tal. a %aterial

that generate! a &oltage hen !"b,ected to %echanical !tre!!. or generate! a %echanicalforce hen &oltage i! applied to it/ If electrode! are plated on oppo!ite face! of a pie5o cr+!tal !"ch a! 7"art5 and a potential i!applied acro!! the!e electrode!. force! ill be e3erted on the bo"nd charge! ithin thecr+!tal. %a*ing the cr+!tal bend/ Re%o&al of the applied &oltage ill %a*e it ret"rn to itoriginal !hape. hich %a+ generate a &oltage in the proce!!/ :!!"%ing that the de&ice i! properl+ %o"nted. !"ch condition! ill allo the cr+!tal to beha&e a! an electro%echanica!+!te% that &ibrate! a! long a! it i! !"b,ected to proper electrical e3citation/

2ig"re 1/ hoto of cr+!talo!cillator! 'left) and the !+%bolfor a cr+!tal o!cillator 'right)

: cr+!tal o!cillator beha&e! li*e a circ"it co%po!ed of an ind"ctor. capacitor. and re!i!tor.re!onating at a preci!e fre7"enc+. i/e/. it! electrical o!cillation attain! %a3i%"% a%plit"deat thi!re!onant fre7"enc+/ The re!onant fre7"enc+ and the 7"alit+ factorQ of a cr+!talo!cillator depend! on the cr+!tal di%en!ion!. the orientation of the !"rface! ith re!pect toit! a3e!. and ho the de&ice i! %o"nted/ The7"alit+ factor of a re!onant circ"it i! a %ea!"re of6 1) ho fa!t the re!pon!e of thecirc"it fall! off a! the e3citation fre7"enc+ %o&e! a a+ fro% the re!onant fre7"enc+# and$) ho large the a%plit"de of the re!pon!e i! at the re!onant fre7"enc+/ : high %ean!that the circ"it re!onate! at a higher a%plit"de and it! re!pon!e fall! off %ore 7"ic*l+ a!the o!cillation fre7"enc+ %o&e! a a+ fro% re!onance/ Cr+!tal o!cillator! can generate fre7"encie! ranging fro% a fe *H5 to a fe ?H5. and 9!ranging fro% !e&eral tho"!and! to !e&eral h"ndred tho"!and!/ The!e e3ceptionall+ high &al"e! and the fact that 7"art5 i! e3tre%el+ !table ith re!pect to ti%e and te%perat"re i!the rea!on for the fre7"enc+ !tabilit+ of cr+!tal o!cillator!/ Cr+!tal o!cillator! are "!"all+ labelled a! 9 T:L9 on !che%atic diagra%!/

: capacitor i! a co%ponent "!ed for !toring electrical charge. and "!"all+ con!i!t! of t o plate! or !heet! of cond"ctor placed &er+ clo!e to 'b"t not to"ching) each other/ :! thecapacitor charge! "p. one of the!e cond"ctor! beco%e! po!iti&el+ charged hile the otherone beco%e! negati&el+ charged/

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Capacitance 'C) i! defined a! the ratio of the charge ' ) !tored in a capacitor to the &oltage'V) acro!! the capacitor/ ?athe%aticall+. therefore. C ( 0V/ The "nit of %ea!"re%ent for capacitance i! the 9farad9. 2. hich i! defined a! co"lo%b0&olt 'co"lo%b and &olt are the

"nit! of %ea!"re%ent for charge and &oltage. re!pecti&el+)/ The higher the capacitance ocapacitor. the greater i! the charge it can !tore for a gi&en &oltage acro!! it/

2ig"re 1/ hoto ofCapacitor! Capacitor! %a+ be connected to each other to for% ne &al"e! of capacitance/ The+ %a+ be connected in !erie! or in parallel. a! !ho n in 2ig"re $/

2ig"re $/ Capacitor! in parallel 'left) and in !erie! 'right) Fhen N capacitance! are connected in!erie! and a &oltage V i! applied acro!! the%. V (V1 < V$ < /// < VN ( 10C1 < $0C$ < /// < N0CN. here i and Vi are thecorre!ponding charge in and &oltage acro!! e&er+ indi&id"al capacitance Ci. re!pecti&el+/Ho e&er. 1 ( $ ( /// ( N. !ince each capacitor in the !erie! e3perience! the !a%ec"rrent or flo of charge/ 2ro% earlier e7"ation!. 0Ceff ( 0C1 < 0C$ < /// < 0CN/Thi! e7"ation %a+ be !i%plified a! follo !6 10Ceff ( 10C1 < 10C$ < /// < 10CN/ Th"!. the reciprocal of the effecti&e capacitance of N capacitor! connected in !erie! i!e7"al to the !"% of the reciprocal! of their indi&id"al capacitance!. i/e/. 10Ceff ( 10C1 / ?o!t 5ener diode!. ho e&er. ha&e

tolerance! of => to 1;>/

Since a 5ener diode i! %eant to operate in re&er!e bia!. it! "!"al application o"ld ha&e itconnected to the circ"it in !"ch a a+ that it! cathode i! %ore po!iti&e than it! anode/Under thi! connection. the 5ener diode ill not cond"ct "nle!! the &oltage at the cathodee3ceed! the anode &oltage b+ %ore than it! 5ener &oltage/ Th"!. a 5ener diode !tart!cond"cting a! !oon a! it i! re&er!e-bia!ed b+ a &oltage e7"al to it! 5ener &oltage/ Once itcond"ct!. the 5ener diode tend! to p"ll do n the &oltage applied acro!! it/ :! !"ch. the

&oltage !een acro!! a cond"cting 5ener diode i! &er+ clo!e to it! 5ener &oltage/ Since a cond"cting 5ener diode %aintain! the &oltage acro!! it at a &al"e aro"nd it! 5ener&oltage. it! %ain p"rpo!e i! to !er&e a! a &oltage reg"lator/ : &er+ !i%ple circ"it thatde%on!trate! thi! i! !ho n in 2ig"re $/ Thi! i! a !h"nt &oltage reg"lator circ"it. !ince the5ener diode i! connected in !h"nt 'parallel) ith the load/ In thi! circ"it. Vo"t ill be%aintained b+ the 5ener diode at the 5ener &oltage le&el e&en if Vin change!. a! long a!Vin e3ceed! the 5ener &oltage/ If Vin increa!e!. the c"rrent flo ing thro"gh the 5ener diode D1 increa!e! a! ell.ca"!ing the &oltage acro!! the re!i!tor R to increa!e hile allo ing the &oltage acro!! the5ener diode to re%ain at the 5ener &oltage le&el/ Of co"r!e. if Vin fall! belo the 5ener&oltage of D1. D1 !top! cond"cting. and Vo"t !tart! falling ith Vin/ Note that thi!circ"it i! al!o a &er+ inefficient a+ to reg"late a &oltage. !ince reg"lation i! achie&ed b+!h"nting c"rrent to gro"nd. hich i! li*e !i%pl+ thro ing the e3ce!! energ+ a a+/

2ig"re $/ : !i%ple Sh"nt Voltage Reg"lator "!ing a 5ener diode

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: t"nnel diode. al!o *no n a! an E!a*i diode. i! a !pecial t+pe of diode that can beoperated at &er+ high fre7"encie!. i/e/. ell into the %icro a&e fre7"enc+ range/ It a!in&ented b+ Leo E!a*i of To*+o T!"!hin Aog+o in 1G= /

: t"nnel diode ha! thi! capabilit+ beca"!e it operate! on the principle of electron t"nnelingeffect/ ?a*ing "!e of e3tre%el+ doped p-t+pe and n-t+pe %aterial!. a t"nnel diodeachie&e! &er+ high concentration! of carrier! that can interact readil+ itho"t ha&ing to pa!! o&er the ,"nction9! potential barrier/ In!tead. the carrier! !i%ple pa!! thro"gh the potential hill/ Thi! i! the electron t"nneling effect %entioned earlier/ The &er+ hea&+ doping of the p-n ,"nction of a t"nnel diode re!"lt! in a bro*en bandgap.!o%e hat ca"!ing the cond"ction band electron !tate! on the n-!ide of the ,"nction to bealigned ith the &alence band hole !tate! on the p-!ide/ T"nnel diode! are "!"all+ fabricated "!ing ger%ani"%. altho"gh galli"% ar!enide and

!ilicon t"nnel diode! al!o e3i!t/ The+ are "!ed in application! !"ch a! o!cillator!.a%plifier!. fre7"enc+ con&erter!. and detector!/ Fhen the for ard bia! &oltage i! initiall+ applied in a t"nnel diode. the c"rrent increa!e!a! the filled electron !tate! in the n-!ide cond"ction band align! ith the e%pt+ &alence band hole !tate! in the p-!ide/ :! the &oltage i! f"rther increa!ed. the!e !tate! begin to%i!align. ca"!ing the c"rrent to decrea!e/ The c"rrent f"rther drop! a! the &oltage i!increa!ed. hich %ean! that the t"nnel diode i! e3hibiting a negati&e re!i!tance "nderthe!e condition!/ Increa!ing the &oltage f"rther e&ent"all+ pre&ent! the occ"rrence ofelectron t"nneling. ca"!ing the t"nnel diode to ,"!t operate li*e a nor%al diode/

2ig"re 1/ hoto of a t"nnel diode 'left) and the t ocirc"it !+%bol! co%%onl+ "!ed for the t"nnel diode'right)

Tran!i!tor Co%%on-Ter%inal Config"ration!

Tran!i!tor circ"it! %a+ be cla!!ified into three config"ration! ba!ed on hich ter%inal i!co%%on to both the inp"t and the o"tp"t of the circ"it/ The!e config"ration! are6 1) theco%%on-e%itter config"ration# $) the co%%on-ba!e config"ration# and ) the co%%on-collector config"ration/ Theco%%on-e%itter 'CE) tran!i!tor config"ration i! !ho n in 2ig"re 1/ In thi!config"ration. the tran!i!tor ter%inal co%%on to both the inp"t and the o"tp"t of the

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circ"it i! the e%itter/ The co%%on-e%itter config"ration. hich i! al!o *no n a! the9gro"nded-e%itter9 config"ration. i! the %o!t idel+ "!ed a%ong the three config"ration!/

2ig"re 1/ Co%%on-E%itter Tran!i!tor Config"ration The inp"t c"rrent and o"tp"t &oltage of the co%%on-e%itter config"ration. hich are the ba!e c"rrent Ib and the collector-e%itter &oltage Vce. re!pecti&el+. are often con!idered athe independent &ariable! in thi! circ"it/ It! dependent &ariable!. on the other hand. are th ba!e-e%itter &oltage Vbe ' hich i! the inp"t &oltage) and the collector c"rrent Ic ' hich i!the o"tp"t c"rrent)/ : plot of the o"tp"t c"rrent Ic again!t the collector-e%itter &oltageVce for different &al"e! of Ib %a+ be dra n for ea!ier anal+!i! of a tran!i!tor9!inp"t0o"tp"t characteri!tic!. a! !ho n in thi!Diagra% of Vce-Ic C"r&e!/ Theco%%on-ba!e 'C@) tran!i!tor config"ration. hich i! al!o *no n a! the 9gro"nded ba!e9 config"ration. i! !ho n in 2ig"re $/ In thi! config"ration. the ter%inal co%%on to both the inp"t and the o"tp"t of the circ"it i! the ba!e/

2ig"re $/ Co%%on-@a!e Tran!i!tor Config"ration The inp"t c"rrent and o"tp"t &oltage of the co%%on-ba!e config"ration. hich are thee%itter c"rrent Ie and the collector-ba!e &oltage Vcb. re!pecti&el+. are often con!idered athe independent &ariable! in thi! circ"it/ It! dependent &ariable!. on the other hand. are the%itter-ba!e &oltage Veb ' hich i! the inp"t &oltage) and the collector c"rrent Ic ' hich i!the o"tp"t c"rrent)/ : plot of the o"tp"t c"rrent Ic again!t the collector-ba!e &oltage Vcbfor different &al"e! of Ie %a+ be dra n for ea!ier anal+!i! of a tran!i!tor9! inp"t0o"tp"tcharacteri!tic!. a! !ho n in thi! Diagra% of Vcb-Ic C"r&e!/ Theco%%on-collector 'CC) tran!i!tor config"ration i! !ho n in 2ig"re / In thi!config"ration. the collector i! co%%on to both the inp"t and the o"tp"t of the circ"it/ Thi!

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i! ba!icall+ the !a%e a! the co%%on-e%itter config"ration. e3cept that the load i! in thee%itter in!tead of the collector/ J"!t li*e in the co%%on-e%itter circ"it. the c"rrentflo ing thro"gh the load hen the tran!i!tor i! re&er!e-bia!ed i! 5ero. ith the collectorc"rrent being &er+ !%all and e7"al to the ba!e c"rrent/ :! the ba!e c"rrent i! increa!ed.the tran!i!tor !lo l+ get! o"t of c"t-off. goe! into the acti&e region. and e&ent"all+

beco%e! !at"rated/ Once !at"rated. the &oltage acro!! the load beco%e! %a3i%"%. hilethe &oltage Vce acro!! the collector and e%itter of the tran!i!tor goe! do n to a &er+ lo&al"e. i/e/. a! lo a! a fe ten! of %illi&olt! for ger%ani"% and ;/$ V for !ilicontran!i!tor!/

2ig"re / Co%%on-Collector Tran!i!tor Config"ration

One a+ of "nder!tanding the ba!ic operation of a bipolar tran!i!tor i! b+ loo*ing at it!Vce-Ic c"r&e!. i/e/. the plot! of it! collector c"rrent Ic &er!"! the &oltage Vce acro!! it!collector and e%itter for different &al"e! of ba!e c"rrent Ib/ The!e c"r&e! are deri&ed fro%a tran!i!tor in co%%on-e%itter config"ration. and ba!icall+ de!cribe the tran!i!tor9!co%%on-e%itter o"tp"t characteri!tic!/

: tran!i!tor circ"it i! !aid to be in co%%on-e%itter config"ration if the e%itter i! theter%inal co%%on to both the inp"t and the o"tp"t/ In the anal+!i! of tran!i!tor circ"it!. theinp"t c"rrent and o"tp"t &oltage are "!"all+ con!idered the independent &ariable!/ Th"!.for the co%%on-e%itter config"ration. the independent &ariable! are the inp"t c"rrent Iband the o"tp"t &oltage Vce. hile the dependent &ariable! are the inp"t &oltage Vbe andthe o"tp"t c"rrent Ic/ The fa%il+ of inp"t characteri!tic c"r&e! %a+ therefore be de!cribed b+ the f"nction f1 herein Vbe ( f1'Vce. Ib). hile the fa%il+ of o"tp"t c"r&e! %a+ bede!cribed b+ the f"nction f$. herein Ic ( f$'Vce. Ib)/ The o"tp"t c"r&e! corre!ponding to f$ are dra n ith the collector-to-e%itter &oltage Vcea! the ab!ci!!a. and the collector c"rrent Ic a! the ordinate/ Different o"tp"t c"r&e! aregenerated for different &al"e! of ba!e c"rrent Ib. hich are all dra n on the !a%e plot/2ig"re 1 !ho ! an e3a%ple of a co%%on-e%itter tran!i!tor circ"it9! Vce-Ic c"r&e! fordifferent &al"e! of Ib/

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2ig"re 1/ The Vce-Ic C"r&e! of an N N tran!i!tor for different&al"e! of Ib 'Co%%on-e%itter Collector Characteri!tic!) The!e co%%on-e%itter Vce-Ic c"r&e! are "!ef"l in choo!ing the opti%"% operating pointof a tran!i!tor "!ed a! an a%plifier/ : tran!i!tor "!ed a! an a%plifier %"!t be operated inthe acti&e region. herein the change in the collector c"rrent 'o"tp"t) i! proportional to thechange in the ba!e c"rrent 'inp"t)/ Thi! linear region i! ideal for a%plification "!e beca"!eit allo ! the o"tp"t a&efor% to be an enlarged 9faithf"l9 cop+ of the inp"t a&efor%/ Thacti&e or linear region in the Vce-Ic c"r&e i! it! flat portion on the right !ide/ Note that thchange in collector c"rrent Ic i! %o!t !en!iti&e to the change in ba!e c"rrent Ib in thi!region/ The !lope of the c"r&e in thi! operating region repre!ent! the reciprocal of the tran!i!tor9!collector or o"tp"t re!i!tance Rc. i/e/. Slope ( Ic0Vce ( 10Rc/ Thi! %ean! that in thi! regionof the c"r&e. the o"tp"t re!i!tance i! relati&el+ high 'bet een 1;-=; * )/ :n a&erage Rc&al"e of ; * in thi! region %a+ be a!!"%ed/ :l!o note that in thi! flat portion of the c"r&e. the collector c"rrent Ic doe!n9t change %"ch

ith the collector-e%itter &oltage Vce for an+ gi&en ba!e c"rrent Ib/ One a+ of "nder!tanding the ba!ic operation of a bipolar tran!i!tor i! b+ loo*ing at it!Vcb-Ic c"r&e!. i/e/. the plot! of it! collector c"rrent Ic &er!"! the &oltage Vcb acro!! it!collector and ba!e for different &al"e! of e%itter c"rrent Ie/ The!e c"r&e! are deri&ed fro%

a tran!i!tor in co%%on-ba!e config"ration. and ba!icall+ de!cribe the tran!i!tor9!co%%on- ba!e o"tp"t characteri!tic!/

: tran!i!tor circ"it i! !aid to be in co%%on-ba!e config"ration if the ba!e i! the ter%inalco%%on to both the inp"t and the o"tp"t/ In the anal+!i! of tran!i!tor circ"it!. the inp"tc"rrent and o"tp"t &oltage are "!"all+ con!idered the independent &ariable!/ Th"!. for theco%%on-ba!e config"ration. the independent &ariable! are the inp"t c"rrent Ie and the

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o"tp"t &oltage Vcb. hile the dependent &ariable! are the inp"t &oltage Veb and the o"tp"c"rrent Ic/ The fa%il+ of inp"t characteri!tic c"r&e! %a+ therefore be de!cribed b+ thef"nction f1 herein Veb ( f1'Vcb. Ie). hile the fa%il+ of o"tp"t c"r&e! %a+ be de!cribed b+ the f"nction f$. herein Ic ( f$'Vcb. Ie)/

The o"tp"t c"r&e! corre!ponding to f$ are dra n ith the collector-to-ba!e &oltage Vcb a!the ab!ci!!a. and the collector c"rrent Ic a! the ordinate/ Different o"tp"t c"r&e! aregenerated for different &al"e! of e%itter c"rrent Ie. hich are all dra n on the !a%e plot/2ig"re 1 !ho ! an e3a%ple of a co%%on-ba!e tran!i!tor circ"it9! Vcb-Ic c"r&e! fordifferent &al"e! of Ie/

2ig"re 1/ The Vcb-Ic C"r&e! of an N N tran!i!tor for different&al"e! of E%itter C"rrent 'Co%%on-@a!e O"tp"t Characteri!tic!)

The!e co%%on-ba!e Vcb-Ic c"r&e! are "!ef"l in di!ting"i!hing bet een the differentregion! of operation of a bipolar tran!i!tor. na%el+. the acti&e. !at"ration. and c"t-offregion!/ The acti&e or linear region. herein the collector ,"nction i! re&er!e-bia!ed hilethe e%itter ,"nction i! for ard-bia!ed. i! characteri5ed b+ the flat or hori5ontal portion! ofthe c"r&e!/ The !at"ration region. in hich both the collector and e%itter ,"nction! arefor ard-bia!ed. lie! in the portion! of the c"r&e! herein Vcb i! ,"!t &er+ !lightl+ abo&e ;V and Ie ;/ La!tl+. the c"t-off region. herein both the collector and e%itter ,"nction!are re&er!e-bia!ed. i! here the c"r&e! are belo Ie (;/

TheJ"nction 2ield Effect Tran!i!tor 'J2ET) i! a t+pe of field effect tran!i!tor ho!e ba!ic

!tr"ct"re con!i!t! of a !e%icond"ctor bar ith oh%ic contact! at the end and hea&il+ dopedregion! on it! oppo!ite !ide!/ If the !e%icond"ctor bar i! %ade of n-t+pe %aterial. then iti! an n-channel J2ET/ The J2ET i! p-channel if the bar i! %ade of p-t+pe %aterial/ Theter%inal! at the end! of the bar corre!pond to the !o"rce and drain of the J2ET/ Thehea&il+ doped region! on the !ide! of the bar are connected to !er&e a! the gate of theJ2ET/ Needle!! to !a+. the gate region! are doped to be of oppo!ite t+pe ith re!pect to thechannel. !o that a p-n ,"nction i! for%ed bet een the channel and the gate region!/

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@+ appl+ing a &oltage acro!! the !o"rce and the drain of a J2ET. c"rrent con!i!ting of%a,orit+ carrier! 'electron! for an n-channel and hole! for a p-channel) i! ca"!ed to flothro"gh the channel/ The c"rrent flo ing thro"gh the channel i! controlled b+ appl+ing agate &oltage Vg! that re&er!e bia!e! the p-n ,"nction for%ed b+ the gate ith re!pect to the

!o"rce/ The higher the Vg! i!. the %ore the p-n ,"nction i! re&er!e-bia!ed. and the iderthe depletion region acro!! the channel beco%e!/ The ider depletion region re!"lt! in anarro er channel. con!e7"entl+ con!tricting the flo of c"rrent thro"gh the channel/Var+ing Vg! therefore &arie! the c"rrent thro"gh the channel for an+ gi&en &oltage acro!the !o"rce and the drain/ The J2ET !tr"ct"re de!cribed abo&e i! no longer practical to "!e beca"!e of the diffic"lt+

ith ha&ing to diff"!e dopant! fro% t o oppo!ite !ide! of a bar/ ?o!t J2ET! b"ilt ontoIC9! no ada+! in&ol&e !ingle-ended geo%etrie! that re7"ire doping for the gate fro% onone !ide of the channel. i/e/. the !"rface of the afer/ Thi! i! achie&ed b+ b"ilding theJ2ET on an epita3iall+ gro n channel o&er a doped !"b!trate that act! a! the !econd gate/

The c"rrent thro"gh the channel of a ?OS2ET or J2ET con!i!t! of onl+ the %a,orit+carrier!. hich i! h+ 2ET! are referred to al!o a! "nipolar tran!i!tor!/

2ig"re 1/ Str"ct"re of a !ingle-ended-geo%etr+ ,"nction 2ET The?etal-O3ide Se%icond"ctor 2ield Effect Tran!i!tor '?OS2ET) or ?OS tran!i!tor i! at+pe of tran!i!tor that con!i!t! of a %etal la+er. an o3ide la+er. and a !e%icond"ctor la+er/The !e%icond"ctor la+er i! "!"all+ in the for% of !ingle-cr+!tal !ilicon !"b!trate doped preci!el+ to perfor% tran!i!tor action/ The o3ide i! "!"all+ in the for% of a !ilicon dio3idela+er that in!"late! the !e%icond"ctor la+er fro% the %etal la+er/ The %etal la+er i! "!eda! contact for pro&iding &oltage inp"t! to the ?OS tran!i!tor/

The ?OS tran!i!tor con!i!t! of three ter%inal!6 a gate. a !o"rce. and a drain/ The!e aree7"i&alent to the ba!e. e%itter. and collector of a bipolar tran!i!tor/ The %etal la+er of th?OS tran!i!tor !er&e! a! the gate. hile the !o"rce and drain are fabricated on the !ilicon!"b!trate/

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Li*e a bipolar tran!i!tor. the c"rrent flo ing thro"gh a ?OS tran!i!tor i! controlled b+ theinp"t at it! gate/ Ho e&er. "nli*e a bipolar tran!i!tor hich i! controlled b+ the a%o"nt ofc"rrent into it! ba!e. a ?OS tran!i!tor i! controlled b+ the &oltage le&el at it! gate/ The !o"rce and drain of a ?OS tran!i!tor are created on the !ilicon !"b!trate in !"ch a a+

that the+ are 9!and iching9 the gate/ The !o"rce and drain are doped to be of the !a%e%aterial t+pe. hich !ho"ld be different fro% the doping recei&ed b+ the !"b!trate/ :?OS tran!i!tor i! referred to a! a -channel ?OS2ET. or?OS. if the !o"rce and drainare p-t+pe. and the !"b!trate i! n-t+pe/ It i! an N-channel ?OS2ET. or N?OS. if the!o"rce and drain are n-t+pe. and the !"b!trate i! p-t+pe/

The area "nder the gate i! *no n a! the channel/ The cond"cti&it+ of the channel %a+ becontrolled thro"gh the &oltage le&el applied to the gate/ 2or in!tance. in an N?OS. the%a,or carrier i! the electron. !o the channel beco%e! %ore cond"cti&e b+ appl+ing a po!iti&e &oltage at the gate. hich tend! to attract %ore electron! fro% the !"b!trate intothe channel/ The la+er for%ed b+ the!e attracted electron! i! *no n a! the 9in&er!ion

la+er9. !ince electron! are the %inorit+ carrier! of the p-!"b!trate/ If the !o"rce of the N?OS i! %ore negati&e than the drain hile a !"fficientl+ po!iti&e&oltage i! applied to the gate. c"rrent o"ld pa!! thro"gh the tran!i!tor/ Re%o&ing the po!iti&e &oltage at the gate o"ld !ignificantl+ decrea!e the cond"cti&it+ of the channel.con!tricting the flo of electron!/ : ?OS tran!i!tor operating in thi! %anner i! *no n a!an enhance%ent-%ode ?OS tran!i!tor. beca"!e it i! nor%all+ open and cond"ct! onl+

hen the channel i! 9enhanced/9 On the other hand. a nor%all+ cond"cting tran!i!tor i!*no n a! a depletion-%ode tran!i!tor. !ince it! cond"ction i! controlled b+ 9depleting9 thenor%all+-pre!ent channel/

2ig"re 1/ Str"ct"re of an Enhance%ent?OS2ET

The ter%9diac9. hich !tand! for9diode for alternating c"rrent9. refer! to a three-la+er t o-ter%inal de&ice that can cond"ct c"rrent in t o direction!/ Ho e&er. a diac onl+ !tart! tocond"ct c"rrent hen the &oltage acro!! it %o%entaril+ e3ceed! a certain thre!hold *no na! it! 9brea*do n &oltage9/

Once triggered b+ a %o%entar+ &oltage higher than it! brea*do n &oltage. the re!i!tanceof the diac decrea!e! abr"ptl+/ Thi! re!"lt! in a !harp increa!e in c"rrent flo ing thro"gh

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the diac and a corre!ponding decrea!e in the &oltage acro!! it/ Thi! cond"cting !tatere%ain! a! long a! the c"rrent flo ing thro"gh the diac i! higher than a c"rrent thre!hold*no n a! the diac9! 9holding c"rrent/9 Once the c"rrent thro"gh a cond"cting diac fall! belo the holding c"rrent. the diac

! itche! bac* to it! high-re!i!tance or non-cond"cting !tate/ rior to being triggered into cond"ction. a non-cond"cting diac e3hibit! negati&e

re!i!tance/ Thi! %ean! that increa!ing the &oltage acro!! a non-cond"cting diac ill ca"!ethe c"rrent flo ing thro"gh it to decrea!e. a! long a! the brea*do n &oltage i! not reached/

2ig"re 1/ hoto of a diac 'left)and the !+%bol for a diac 'right)

?o!t diac! e3hibit a brea*do n &oltage of aro"nd ; V/ Unli*e other th+ri!tor! !"ch a!theSCR or thetriac. the diac ha! no gate electrode ith hich it can be triggered/ : diac9! pri%ar+ application i! for triggering another de&ice/ Diac! are al!o *no n a! !+%%etrical trigger diode! beca"!e of the !+%%etr+ e3hibited b+their V-I characteri!tic c"r&e!/ @eca"!e of thi! !+%%etr+. the t o ter%inal! of the diac arenot called 9anode9 and 9cathode9. and are in!tead referred to a! ?T1 and ?T$/ : Silicon-Controlled Rectifier 'SCR) i! a fo"r-la+er 'p-n-p-n) !e%icond"ctor de&ice thatdoe!n9t allo c"rrent to flo "ntil it i! triggered and. once triggered. ill onl+ allo theflo of c"rrent in one direction/ It ha! three ter%inal!6 1) an inp"t control ter%inal referreto a! a9gate9# $) an o"tp"t ter%inal *no n a! the9anode9# and ) a ter%inal *no n a! a9cathode9. hich i! co%%on to both the gate and the anode/ SCR9! are generall+ "!ed for ! itching and po er control p"rpo!e! in :C and high-po ercirc"it!/ The SCR i! a de&ice that fall! "nder a gro"p of de&ice! *no n a! 9th+ri!tor!9.

hich refer to de&ice! that ha&e a 8-la+er or p-n-p-n !tr"ct"re/ The ter% 9!ilicon-controlrectifier9 i! a trade na%e "!ed b+ 4eneral Electric in 1G= to refer to thi! t+pe of th+ri!tor

2ig"re 1/ hoto of &ario"! SCR9!'left) and the circ"it !+%bol for anSCR 'right)

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:n SCR %a+ be tho"ght of a! a rectifier ho!e abilit+ to cond"ct c"rrent can be controlled"!ing a third ter%inal *no n a! a 9gate9/ Fhile "ntriggered. an SCR ill pre&ent an+c"rrent to flo thro"gh it. e3cept for a &er+ !%all lea*age c"rrent ca"!ed b+ non-idealcondition!/ The SCR i! triggered to t"rn on if the &oltage acro!! it! gate and it! cathode

e3ceed! a certain thre!hold le&el/ Once an SCR ha! been triggered. it ill re%ain 9on9 e&en if the triggering gate &oltage ire%o&ed. "ntil the c"rrent flo ing thro"gh it fall! belo a le&el *no n a! it! 9holdingc"rrent9/ Th"!. a cond"cting SCR ill contin"e to cond"ct a! long a! the c"rrent flo ingthro"gh it i! greater than the holding c"rrent/ In nor%al :C application!. an SCR i! t"rnedoff a"to%aticall+ d"ring the half-c+cle herein the &oltage and c"rrent are belo 5ero/ The p-n-p-n !tr"ct"re of an SCR %a+ be %odeled in ter%! of a N and an N N tran!i!toa! !ho n in 2ig"re $/ It can ea!il+ be !een fro% thi! diagra% h+ an SCR re%ain! 9on9once triggered. e&en if the triggering gate &oltage i! re%o&ed/ :ppl+ing !"fficient

triggering &oltage at the gate dri&e! the N N tran!i!tor to cond"ct/ Thi!. in t"rn. p"ll!do n the N 9! ba!e &oltage. ca"!ing the N to cond"ct/ The cond"cting N then!"pplie! the ba!e c"rrent to the N N tran!i!tor to *eep it cond"cting/ Unle!! the !"ppl+ ofc"rrent to the ba!e of the N N i! c"t off. the circ"it ill contin"e cond"cting "nder thi! 9oncondition/

2ig"re $/ The E7"i&alent Circ"it 'left) and Str"ct"re 'right) of an SCR SCR9!. hich can ha&e &oltage rating! of "p to $.=;; &olt! and c"rrent rating! of "p to

.;;; a%pere!. are enco"ntered in %an+ :C and high-po er application!/ E3a%ple! ofapplication! for SCR9! incl"de6 1) po er ! itching# $) pha!e control# ) batter+ chargin8) po er in&erter!# =) %otor ! itching and control# ) high-&oltage DC con&er!ion# et

: Triac i! a three-ter%inal electronic co%ponent that f"nction! a! a gate-controlled bidirectional ! itch. pri%aril+ for :C circ"it!/ It! !tr"ct"re i! ba!icall+ e7"i&alent to t ooppo!itel+-facing!ilicon-controlled rectifier! 'SCR9!) connected in parallel. ith theirgate! connected together/ Fherea! an SCR i! capable of cond"cting c"rrent in onl+ onedirection. a triac can cond"ct c"rrent in both direction! beca"!e of it! d"al-SCRconfig"ration/

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The %ain ter%inal! of a triac are often de!ignated a!9?T19and9?T$9. hile it! inp"tcontrol ter%inal i! referred to a! a9gate9. a! %entioned earlier/ Fhene&er a !"fficient po!iti&e or negati&e &oltage i! applied at the gate of a triac. one of it! t o SCR9! t"rn onca"!ing c"rrent to flo thro"gh the triac/ Fhich SCR i! cond"cting at an+ one ti%edepend! on the polarit+ of the &oltage acro!! the triac/

2ig"re 1/ hoto of a triac 'left)and the circ"it !+%bol for a triac'right)

J"!t li*e an SCR. a triac ill contin"e to cond"ct once it i! t"rned on. e&en if the triggering

gate &oltage i! re%o&ed/ Ho e&er. the c"rrent flo ing thro"gh the triac %"!t re%ainabo&e a certain le&el. *no n a! the9holding c"rrent9. in order to *eep the triac cond"cting/If the c"rrent thro"gh the triac fall! belo the holding c"rrent. the triac ! itche! off. andneed! to be triggered again in order to cond"ct/

: triac i! a good ! itching de&ice for :C load!. !"ch a! incande!cent b"lb! and :C%otor!/ In nor%al :C application!. a triac t"rn! off hen the !in"!oidal c"rrent cro!!e! the5ero le&el/ Note that hen a triac i! "!ed to dri&e ind"cti&e load!. the c"rrent i! %orediffic"lt to dri&e to 5ero '!ince ind"ctor! oppo!e in!tantaneo"! change! in c"rrent). and thi!%ight pre!ent !o%e i!!"e! d"ring ! itch-off/ Th"!. thi! pheno%enon %"!t be con!idered

hen de!igning an application herein a triac i! "!ed to po er an ind"cti&e load/ The point ithin the c+cle of the !ine a&e at hich a triac i! triggered %a+ al!o be preci!el+ ti%ed. !"ch that the percentage of po er deli&ered to the load %a+ al!o becontrolled ith a triac/ E3a%ple! of application! for triac! incl"de6 1) ! itching and di%%ing for :Cincande!cent b"lb!# $) !peed control! for appliance! ith electric %otor!. e/g/. electricfan!# and ) interfacing of :C appliance! to digital co%p"ter !+!te%!/ The follo ing para%eter! %"!t be con!idered hen !electing a triac6 1) for ard andre&er!e brea*o&er &oltage# $) %a3i%"% load c"rrent# ) %ini%"% holding c"rrent# 8)&oltage and c"rrent trigger !pecification!# =) ! itching !peed!# and ) %a3i%"% dV0dt/

Reactance ' ) i! defined a! the ratio of the :C &oltage to the :C c"rrent in an :C circ"it.a! ca"!ed b+ the pre!ence of a reacti&e co%ponent in the circ"it. i/e/. a capacitor or anind"ctor/ The reactance of a capacitor or ind"ctor i! therefore li*e there!i!tance of are!i!tor. e3cept that the reactance of a capacitor or ind"ctor i! not con!tant - it &arie! iththe fre7"enc+ of the !ignal acro!! the capacitor or thro"gh the ind"ctor/ Reactance i! al!oe3pre!!ed in oh%!/

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The pre!ence of a capacitor or an ind"ctor in a circ"it i%pede! change! in &oltage orc"rrent ithin the circ"it/ Specificall+. the &oltage acro!! a capacitor can not changein!tantaneo"!l+. in the !a%e a+ that c"rrent flo ing thro"gh an ind"ctor can not change

in!tantaneo"!l+/ :! !"ch. the pre!ence of a capacitor or ind"ctor in an :C circ"itintrod"ce! a pha!e !hift bet een the &oltage and c"rrent !ignal! in the circ"it/ In an :C circ"it here both re!i!tance and reactance e3i!t. the effecti&e ratio of &oltage toc"rrent i! *no n a! the i%pedance of the circ"it. hich i! gi&en b+ the e7"ation ( R < , . or ( S RT'R $ < $)/ I%pedance i! therefore the o&er-all abilit+ of a circ"it to9i%pede9 the flo of c"rrent for a gi&en &oltage. and it con!i!t! of t o co%ponent!6re!i!tance and reactance/ :!!"%e that a !in"!oidal &oltage ith fre7"enc+ f 'in H5) i! applied acro!! a capacitor

ith capacitance C/ The reactance C of the capacitor i! then gi&en b+ the e7"ation6C

( 1 0 '$ fC) ( 1 0 WChere W ( $ f i! the ang"lar fre7"enc+ in radian! per !econd/ Th"!.the reactance C of a capacitor decrea!e! a! the fre7"enc+ f increa!e!. and increa!e! a! fdecrea!e!/ Thi! i! h+ a capacitor i! "!ed to bloc* the DC co%ponent of an :C !ignal/2"rther%ore. the c"rrent !ine a&e thro"gh a capacitor i! G; degree! ahead of the &oltage!ine a&e acro!! it/ On the other hand. the reactance L of an ind"ctor i! gi&en b+ the e7"ationL ( $ fL (WL. hich %ean! that the reactance of an ind"ctor increa!e! a! the fre7"enc+ of the !ignalthro"gh it increa!e!/ 2"rther%ore. the c"rrent !ine a&e thro"gh an ind"ctor lag! the&oltage !ine a&e acro!! it b+ G; degree!/

@eca"!e the reactance e3hibited b+ a capacitor decrea!e! a! fre7"enc+ increa!e!. it!reactance i! con!idered negati&e/ Th"!. a reactance that9! le!! than ; %ean! that it i!capaciti&e/ Si%ilarl+. a reactance that9! greater than ; %ean! that it i! ind"cti&e/ Reactane7"al! 5ero in a p"rel+ re!i!ti&e circ"it/ S"!ceptance '@) i! the reciprocal of reactance. i/e/.@ ( 1 0 / I%pedance ' ) i! the o&er-all %ea!"re of the abilit+ of a circ"it to re!i!t the flo ofalternating c"rrent "nder a gi&en a/c/ &oltage e3citation/ It %a+ be e3pre!!ed a! ( V 0 I

here V and I are the a/c/ &oltage applied to and c"rrent flo ing thro"gh the circ"it/ It!"nit of %ea!"re%ent i! the oh% '&olt0a%pere)/

I%pedance con!i!t! of t o co%ponent! - re!i!tance and reactance/ : good "nder!tandingof hat i%pedance i! and ho it i! related to re!i!tance and reactance i! i%portant in theanal+!i! of &oltage-c"rrent relation!hip! in an :C circ"it that con!i!t! of re!i!tor! a! ella! reacti&e co%ponent! 'capacitor! and ind"ctor!)/ 2or %ore detail! abo"t re!i!tance andreactance. plea!e !ee the!e !eparate article!6Re!i!tance#Reactance/

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In an :C circ"it that con!i!t of a re!i!tance R in!erie! ith a reactance .the follo inge7"ation! appl+6

( S RT'R $ < $)#X ( tan-1' 0 R) p/f/ ( co! X ( R 0

here6 i! the i%pedance of the circ"it#R i! the re!i!tance of the circ"it#

i! the reactance of the circ"it#X i! the pha!e angle bet een the &oltage and c"rrent !ignal!#and p/f/ i! the po er factor! of the circ"it. hich i! the ratio of tr"e po er to apparent po er of the circ"it/ In an :C circ"it that con!i!t of a re!i!tance R in parallel ith a reactance .the follo inge7"ation! appl+6

( R 0 S RT'R $ < $)#

X ( tan-1

'R 0 ) p/f/ ( co! X ( 0R here6 i! the i%pedance of the circ"it#

R i! the re!i!tance of the circ"it# i! the reactance of the circ"it#

X i! the pha!e angle bet een the &oltage and c"rrent !ignal!#and p/f/ i! the po er factor! of the circ"it. hich i! the ratio of tr"e po er to apparent po er of the circ"it/ :! !ho n in the e7"ation! abo&e. the pre!ence of either a capacitor or an ind"ctor 'or both) in a circ"it prod"ce! a pha!e !hift X bet een the &oltage and c"rrent ac !ignal!/ Thi! pha!e !hift bet een &oltage and c"rrent re!"lt! in reacti&e po er hich can not do real

or*/ In !"ch a ca!e. the tr"e po er of the circ"it i! ,"!t a fraction 'denoted b+ the po erfactor) of it! apparent po er/ :d%ittance 'B) i! the reciprocal of reactance. i/e/.B ( 1 0 / The "nit of %ea!"re%ent forad%ittance i! the !ie%en! 'S)/

Digital Electronic! Digital Electronic! refer! to the field of electronic! that deal! ith digital !ignal!. i/e/.!ignal! that e3i!t at di!crete or 7"anti5ed le&el! onl+/ In fact. digital electronic! a! *no ntoda+ deal! ith !ignal! that are repre!ented b+ onl+ t o di!crete le&el! or 9binar+ !tate!9and ;/ : le&el 9;9. or 9lo 9 !tate. %a+ be repre!ented b+ 5ero &olt '; V). hile a le&el 9199high9 !tate. %a+ be repre!ented b+ a higher &oltage. !a+ = V/

Digital electronic! in&ol&e! the !torage. proce!!ing. recei&ing. and tran!%i!!ion ofinfor%ation in the for% of digital !ignal!. or a train of 9lo 9 '; V) and 9high9 '= V) p"l!e!that corre!pond to ;9! and 19!. re!pecti&el+/

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The oppo!ite of a digital !ignal i! ananalog !ignal. hich i! defined a! a &ar+ing andcontin"o"! !ignal/

Digital !ignal! %a+ be con&erted into analog !ignal! and &ice &er!a b+ de&ice! *no n a

digital-to-analog con&erter! 'D:C9!) and analog-to-digital con&erter! ':DC9!) .re!pecti&el+/

Re!i!tor-Tran!i!tor Logic 'RTL)

Re!i!tor-Tran!i!tor Logic. orRTL. refer! to the ob!olete technolog+ for de!igning andfabricating digital circ"it! that e%plo+ logic gate! con!i!ting of nothing b"t tran!i!tor! andre!i!tor!/ RTL gate! are no !eldo% "!ed. if at all. in %odern digital electronic! de!ign beca"!e it ha! !e&eral dra bac*!. !"ch a! b"l*ine!!. lo !peed. li%ited fan-o"t. and poornoi!e %argin/ : ba!ic "nder!tanding of hat RTL i!. ho e&er. o"ld be helpf"l to an+engineer ho i!he! to get fa%iliari5ed ith TTL. hich for the pa!t %an+ +ear! ha! beco%e idel+ "!ed in digital de&ice! !"ch a! logic gate!. latche!. b"ffer!. co"nter!. andthe li*e/

2ig"re 1 !ho ! an e3a%ple of an N-inp"t RTL NOR gate/ It con!i!t! of N tran!i!tor!.ho!e collector! are all tied "p to Vcc thro"gh a co%%on re!i!tor. and ho!e e%itter! are

all gro"nded/ Their ba!e! indi&id"all+ act a! inp"t! for inp"t &oltage! Vi 'i ( 1.$.///.N).hich repre!ent inp"t logic le&el!/ The o"tp"t Vo i! ta*en acro!! the collector- re!i!tor

node and gro"nd/ Vo i! onl+ 9high9 if the inp"t! to the ba!e! of all the tran!i!tor! are 9lo 9

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2ig"re 1/ : !i%ple N-inp"t RTL NOR 4ate

One of the earlie!t gate! "!ed in integrated circ"it! i! a !pecial t+pe of RTL gate *no n a!the direct-co"pled tran!i!tor logic 'DCTL) gate/ : DCTL gate i! one herein the ba!e! of

the tran!i!tor! are connected directl+ to inp"t! itho"t an+ ba!e re!i!tor!/ Th"!. the RTL NOR gate !ho n in 2ig"re 1 beco%e! a DCTL NOR gate if all the ba!e re!i!tor! 'Rb9!) areeli%inated/ Fitho"t the ba!e re!i!tor!. DCTL gate! are %ore econo%ical and !i%pler tofabricate onto integrated circ"it! than RTL gate! ith ba!e re!i!tor!/

The %ain dra bac* of DCTL gate! i! that the+ !"ffer fro% a pheno%enon *no n a!c"rrent hogging/ Ideall+. !e&eral tran!i!tor! that are connected in parallel ill !hare theload c"rrent e7"all+ a%ong the%!el&e! hen the+ are all bro"ght into !at"ration/ In thereal orld. ho e&er. the !at"ration point! of different tran!i!tor! are attained ith differentle&el! of inp"t &oltage! to the ba!e 'Vbe)/ :! !"ch. tran!i!tor! that are in parallel and !hare

the !a%e inp"t &oltage ' hich are co%%onl+ enco"ntered in DCTL circ"it!) do not !harethe load c"rrent e&enl+ a%ong the%!el&e!/

In fact. once the tran!i!tor ith the lo e!t Vbe!at !at"rate!. the other tran!i!tor! are pre&ented fro% !at"rating the%!el&e!/ Thi! ca"!e! the !at"rated tran!i!tor to 9hog9 the loc"rrent. i/e/. it carrie! the b"l* of the load c"rrent herea! tho!e tran!i!tor! that ere pre&ented fro% !at"rating carrie! a %ini%al portion of it/ C"rrent hogging. hich pre&ented DCTL fro% beco%ing idel+ "!ed. i! largel+ a&oided in RTL circ"it! !i%pl+ bretaining the ba!e re!i!tor!/

RTL gate! al!o e3hibit li%ited 9fan-o"t!9/ The fan-o"t of a gate i! the abilit+ of it! o"tp"t tdri&e !e&eral other gate!/ The %ore gate! it can dri&e. the higher i! it! fan-o"t/ The fan-oof a gate i! li%ited b+ the c"rrent that it! o"tp"t can !"ppl+ to the gate inp"t! connected toit hen the o"tp"t i! at logic 919. !ince at thi! !tate it %"!t be able to dri&e the connectedinp"t tran!i!tor! into !at"ration/

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:nother ea*ne!! of an RTL gate i! it! poor noi!e %argin/ The noi!e %argin of a logicgate for logic le&el 9;9. ;. i! defined a! the difference bet een the %a3i%"% inp"t &oltathat it ill recogni5e a! a 9;9 'Vil) and the %a3i%"% &oltage that %a+ be applied to it a! a9;9 'Vol of the dri&ing gate connected to it)/ 2or logic le&el 919. the noi!e %argin 1 i! tdifference bet een the %ini%"% inp"t &oltage that %a+ be applied to it a! a 919 'Voh of tdri&ing gate connected to it) and the %ini%"% inp"t &oltage that it ill recogni5e a! a 91'Vih)/ ?athe%aticall+. ; ( Vil-Vol and 1 ( Voh-Vih/ :n+ noi!e that ca"!e! a noi!e%argin to be o&erco%e ill re!"lt in a 9;9 being erroneo"!l+ read a! a 919 or &ice &er!a/other ord!. noi!e %argin i! a %ea!"re of the i%%"nit+ of a gate fro% reading an inp"tlogic le&el incorrectl+/

In an RTL circ"it. the collector o"tp"t of the dri&ing tran!i!tor i! directl+ connected to the ba!e re!i!tor of the dri&en tran!i!tor/ Circ"it anal+!i! o"ld ea!il+ !ho that in !"ch anarrange%ent. the difference! bet een Vil and Vol. and bet een Voh and Vih. are not thatlarge/ Thi! i! h+ RTL gate! are *no n to ha&e poor noi!e %argin! in co%pari!on toDTLandTTL gate!/

Diode-Tran!i!tor Logic 'DTL)

Diode-Tran!i!tor Logic. orDTL. refer! to the technolog+ for de!igning and fabricatingdigital circ"it! herein logic gate! e%plo+ both diode! and tran!i!tor!/ DTL offer! betternoi!e %argin! and greater fan-o"t! thanRTL. b"t !"ffer! fro% lo !peed. e!peciall+ in

co%pari!on to TTL/RTL allo ! the con!tr"ction of NOR gate! ea!il+. b"t N:ND gate! are relati&el+ %orediffic"lt to get fro% RTL/ DTL. ho e&er. allo ! the con!tr"ction of !i%ple N:ND gate!fro% a !ingle tran!i!tor. ith the help of !e&eral diode! and re!i!tor!/

2ig"re 1 !ho ! an e3a%ple of an -inp"t DTL N:ND gate/ It con!i!t! of a !ingletran!i!tor config"red a! an in&erter. hich i! dri&en b+ a c"rrent that depend! on theinp"t! to the three inp"t diode! D1-D /

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2ig"re 1/ : !i%ple -inp"t DTL N:ND 4ate

In the N:ND gate in 2ig"re 1. the c"rrent thro"gh diode! D: and D@ ill onl+ be largeeno"gh to dri&e the tran!i!tor into !at"ration and bring the o"tp"t &oltage Vo to logic 9;9 iall the inp"t diode! D1-D are 9off9. hich i! tr"e hen the inp"t! to all of the% are logic919/ Thi! i! beca"!e hen D1-D are not cond"cting. all the c"rrent fro% Vcc thro"gh R

ill go thro"gh D: and D@ and into the ba!e of the tran!i!tor. t"rning it on and p"lling Voto near gro"nd/

Ho e&er. if an+ of the diode! D1-D get! an inp"t &oltage of logic 9;9. it get! for ard- bia!ed and !tart! cond"cting/ Thi! cond"cting diode 9!h"nt!9 al%o!t all the c"rrent a a+fro% the re&er!e-bia!ed D: and D@. li%iting the tran!i!tor ba!e c"rrent/ Thi! force! thetran!i!tor to t"rn off. bringing "p the o"tp"t &oltage Vo to logic 919/

One ad&antage of DTL o&er RTL i! it! better noi!e %argin/ The noi!e %argin of a logicgate for logic le&el 9;9. ;. i! defined a! the difference bet een the %a3i%"% inp"t &oltathat it ill recogni5e a! a 9;9 'Vil) and the %a3i%"% &oltage that %a+ be applied to it a! a9;9 'Vol of the dri&ing gate connected to it)/ 2or logic le&el 919. the noi!e %argin 1 i! tdifference bet een the %ini%"% inp"t &oltage that %a+ be applied to it a! a 919 'Voh of tdri&ing gate connected to it) and the %ini%"% inp"t &oltage that it ill recogni5e a! a 91'Vih)/ ?athe%aticall+. ; ( Vil-Vol and 1 ( Voh-Vih/ :n+ noi!e that ca"!e! a noi!e%argin to be o&erco%e ill re!"lt in a 9;9 being erroneo"!l+ read a! a 919 or &ice &er!a/other ord!. noi!e %argin i! a %ea!"re of the i%%"nit+ of a gate fro% reading an inp"tlogic le&el incorrectl+/

In a DTL circ"it. the collector o"tp"t of the dri&ing tran!i!tor i! !eparated fro% the ba!ere!i!tor of the dri&en tran!i!tor b+ !e&eral diode!/ Circ"it anal+!i! o"ld ea!il+ !ho thatin !"ch an arrange%ent. the difference! bet een Vil and Vol. and bet een Voh and Vih. are%"ch larger than tho!e e3hibited b+ RTL gate!. herein the collector of the dri&ingtran!i!tor i! directl+ connected to the ba!e re!i!tor of the dri&en tran!i!tor/ Thi! i! h+DTL gate! are *no n to ha&e better noi!e %argin! than RTL gate!/

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One proble% that DTL doe!n9t !ol&e i! it! lo !peed. e!peciall+ hen the tran!i!tor i! being t"rned off/ T"rning off a !at"rated tran!i!tor in a DTL gate re7"ire! it to fir!t pa!!thro"gh the acti&e region before going into c"t-off/ C"t-off. ho e&er. ill not be reached"ntil the !tored charge in it! ba!e ha! been re%o&ed/ The di!!ipation of the ba!e chargeta*e! ti%e if there i! no a&ailable path fro% the ba!e to gro"nd/ Thi! i! h+ !o%e DTLcirc"it! ha&e a ba!e re!i!tor that9! tied to gro"nd. b"t e&en thi! re7"ire! !o%e trade-off!/:nother proble% ith t"rning off the DTL o"tp"t tran!i!tor i! the fact that the effecti&ecapacitance of the o"tp"t need! to charge "p thro"gh Rc before the o"tp"t &oltage ri!e! tothe final logic 919 le&el. hich al!o con!"%e! a relati&el+ large a%o"nt of ti%e/TTL.ho e&er. !ol&e! the !peed proble% of DTL elegantl+/

Tran!i!tor-Tran!i!tor Logic 'TTL)

Tran!i!tor-Tran!i!tor Logic. orTTL. refer! to the technolog+ for de!igning and fabricatingdigital integrated circ"it! that e%plo+ logic gate! con!i!ting pri%aril+ of bipolartran!i!tor!/ It o&erco%e! the %ain proble% a!!ociated ith DTL. i/e/. lac* of !peed/

The inp"t to a TTL circ"it i! al a+! thro"gh the e%itter'!) of the inp"t tran!i!tor. hiche3hibit! a lo inp"t re!i!tance/ The ba!e of the inp"t tran!i!tor. on the other hand. i!connected to the Vcc line. hich ca"!e! the inp"t tran!i!tor to pa!! a c"rrent of abo"t 1/%: hen the inp"t &oltage to the e%itter'!) i! logic 9;9. i/e/. near gro"nd/ Letting a TTLinp"t 9float9 'left "nconnected) ill "!"all+ %a*e it go to logic 919. b"t !"ch a !tate i!

&"lnerable to !tra+ !ignal!. hich i! h+ it i! good practice to connect TTL inp"t! to Vcc"!ing 1 *oh% p"ll-"p re!i!tor!/

The %o!t ba!ic TTL circ"it ha! a !ingle o"tp"t tran!i!tor config"red a! an in&erter ith it!e%itter gro"nded and it! collector tied to Vcc ith a p"ll-"p re!i!tor. and ith the o"tp"tta*en fro% it! collector/ ?o!t TTL circ"it!. ho e&er. "!e a tote% pole o"tp"t circ"it.

hich replace! the p"ll-"p re!i!tor ith a Vcc-!ide tran!i!tor !itting on top of the 4ND-!ide o"tp"t tran!i!tor/ The e%itter of the Vcc-!ide tran!i!tor ' ho!e collector i! tied toVcc) i! connected to the collector of the 4ND-!ide tran!i!tor ' ho!e e%itter i! gro"nded) b+ a diode/ The o"tp"t i! ta*en fro% the collector of the 4ND-!ide tran!i!tor/ 2ig"re 1

!ho ! a ba!ic $-inp"t TTL N:ND gate ith a tote%-pole o"tp"t/

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2ig"re 1/ : $-inp"t TTL N:ND 4ate ith a Tote% ole O"tp"t Stage

In the TTL N:ND gate of 2ig"re 1. appl+ing a logic 919 inp"t &oltage to both e%itterinp"t! of T1 re&er!e-bia!e! both ba!e-e%itter ,"nction!. ca"!ing c"rrent to flo thro"gh R1into the ba!e of T$. hich i! dri&en into !at"ration/ Fhen T$ !tart! cond"cting. the !tored ba!e charge of T di!!ipate! thro"gh the T$ collector. dri&ing T into c"t-off/ On the othehand. c"rrent flo ! into the ba!e of T8. ca"!ing it to !at"rate and p"ll do n the o"tp"t&oltage Vo to logic 9;9. or near gro"nd/ :l!o. !ince T i! in c"t-off. no c"rrent ill flofro% Vcc to the o"tp"t. *eeping it at logic 9;9/ Note that T$ al a+! pro&ide!co%ple%entar+ inp"t! to the ba!e! of T and T8. !"ch that T and T8 al a+! operate inoppo!ite region!. e3cept d"ring %o%entar+ tran!ition bet een region!/

On the other hand. appl+ing a logic 9;9 inp"t &oltage to at lea!t one e%itter inp"t of T1 ifor ard-bia! the corre!ponding ba!e-e%itter ,"nction. ca"!ing c"rrent to flo o"t of thate%itter/ Thi! ca"!e! the !tored ba!e charge of T$ to di!charge thro"gh T1. dri&ing T$ intoc"t-off/ No that T$ i! in c"t-off. c"rrent fro% Vcc ill be di&erted to the ba!e of Tthro"gh R . ca"!ing T to !at"rate/ On the other hand. the ba!e of T8 ill be depri&ed ofc"rrent. ca"!ing T to go into c"t-off/ Fith T8 in c"t-off and T in !at"ration. the o"tp"t Voi! p"lled "p to logic 919. or clo!er to Vcc/

O"tp"t! of different TTL gate! that e%plo+ the tote%-pole config"ration %"!t not beconnected together !ince difference! in their o"tp"t logic ill ca"!e large c"rrent! to flofro% the logic 919 o"tp"t to the logic 9;9 o"tp"t. de!tro+ing both o"tp"t !tage!/ The o"tp"t a t+pical TTL gate "nder nor%al operation can !in* c"rrent! of "p to 1 %:/

The noi!e %argin of a logic gate for logic le&el 9;9. ;. i! defined a! the difference bet eethe %a3i%"% inp"t &oltage that it ill recogni5e a! a 9;9 'Vil) and the %a3i%"% &oltagethat %a+ be applied to it a! a 9;9 'Vol of the gate dri&ing it)/ 2or logic le&el 919. the noi!%argin 1 i! the difference bet een the %ini%"% inp"t &oltage that %a+ be applied to ita! a 919 'Voh of the gate dri&ing it) and the %ini%"% inp"t &oltage that it ill recogni5e a 919 'Vih)/ ?athe%aticall+. ; ( Vil-Vol and 1 ( Voh-Vih/ :n+ noi!e that ca"!e! a noi!e

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%argin to be o&erco%e ill re!"lt in a 9;9 being erroneo"!l+ read a! a 919 or &ice &er!a/other ord!. noi!e %argin i! a %ea!"re of the i%%"nit+ of a gate fro% reading an inp"tlogic le&el incorrectl+/ 2or TTL. Vil ( ;/ V and Vol ( ;/8V. !o ; ( ;/8V. and Voh ( $/8Vand Vih ( $/; V. !o 1 ( ;/8V/ The!e noi!e %argin! are not a! good a! the noi!e %argin!e3hibited b+ DTL/

:! %entioned earlier. TTL ha! a %"ch higher !peed thanDTL/ Thi! i! d"e to the fact thathen the o"tp"t tran!i!tor 'T8 in 2ig"re 1) i! t"rned off. there i! a path for the !tored

charge in it! ba!e to di!!ipate thro"gh. allo ing it to reach c"t-off fa!ter than a DTL o"tp"ttran!i!tor/ :t the !a%e ti%e. the e7"i&alent capacitance of the o"tp"t i! charged fro% Vccthro"gh T and the o"tp"t diode. allo ing the o"tp"t &oltage to ri!e %ore 7"ic*l+ to logic919 than in a DTL o"tp"t herein the o"tp"t capacitance i! charged thro"gh a re!i!tor/

The co%%ercial na%e! of digital IC9! that e%plo+ TTL !tart ith 9 89. e/g/. 8;;. 8$88etc/ ?o!t TTL de&ice! no ada+!. ho e&er. are na%ed 9 8LS 9. ith the 9LS9 !tandin

for 9lo po er Schott*+9/ Lo po er !chott*+ TTL de&ice! e%plo+ a Schottl+ diode.hich i! "!ed to li%it the &oltage bet een the collector and the ba!e of a tran!i!tor. %a*ingit po!!ible to de!ign TTL gate! that "!e !ignificantl+ le!! po er to operate hile allo inghigher ! itching !peed!/

@oolean :lgebra

@oolean :lgebra. al!o *no n a! the 9algebra of logic9. i! a branch of %athe%atic! that i!!i%ilar in for% to algebra. b"t dealing ith logical in!tead of n"%erical relation!hip!/ It

a! in&ented b+ 4eorge @oole. after ho% thi! !+!te% a! na%ed/ Th"!. in!tead of&ariable! that repre!ent n"%erical 7"antitie! a! in con&entional algebra. @oolean algebrahandle! &ariable! that repre!ent t o t+pe! of logic propo!ition!6 9tr"e9 and 9fal!e9/

@oolean algebra ha! beco%e the %ain corner!tone of digital electronic!. !ince the latteral!o operate! ith t o logic !tate!. 919 and 9;9. repre!ented b+ t o di!tinct &oltage le&el!@oolean algebra9! for%al interpretation of logical operator! :ND. OR. and NOT ha!allo ed the !+!te%atic de&elop%ent of co%ple3 digital !+!te%! fro% !i%plelogic gate!.

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that no not onl+ incl"de circ"it! that perfor% %athe%atical operation!. b"t intricate data proce!!ing a! ell/ Table! 1 to 8 !"%%ari5e the definition! of logical operator! and their ba!ic %athe%atical propertie! a! repre!ented in @oolean algebra/

Table 1/ Ele%entar+ Logic 4ate :ction!

OR ;


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co%ple%ent! of the indi&id"al &ariable!/ De ?organ9! Theore% applie! to an+ arbitrar+n"%ber of &ariable!/

The i%portant i%plication of De ?organ9! Theore% i! that an+ logic gate or circ"it can be

replaced b+ an e7"i&alent circ"it co%po!ed of other gate!. a! long a! the NOT f"nction ca be pro&ided b+ at lea!t one of the !"b!tit"te gate!/ Thi! i! "!ef"l in digital electronic!de!ign herein there i! a need to %ini%i5e the &ariet+ and n"%ber of logic gate IC9! "!ed

Table 1 !ho ! the %athe%atical for%! of De ?organ9! Theore%/ Table 1/ De ?organ9! Theore%

: Y @ ( : < @: < @ ( : Y @

: Y @ Y C YYYY ( : < @ efficienc+ i!attainable). !ince the a%plif+ing de&ice i! al a+! cond"cting hether or not an inp"t!ignal i! applied/

Class ! "0% of the input signal is used (a = 1#0 or !

: Cla!! @ a%plifier i! one ho!e operating point i! at an e3tre%e end of it! characteri!tic.!o that either the 7"ie!cent c"rrent or the 7"ie!cent &oltage i! al%o!t 5ero/ If a !in"!oidalinp"t &oltage i! "!ed. the a%plification of a Cla!! @ a%plifier ta*e! place onl+ for =;> ofthe c+cle. e/g/. the a%plif+ing de&ice i! ! itched off half of the ti%e/ : Cla!! @ a%plifiercan attain an efficienc+ of "p to /=>/ Ho e&er. a Cla!! @ a%p e3hibit! a higherdi!tortion than an e7"i&alent Cla!! : a%p/

Cla!! :@ $ ore than "0% &ut less than 100% is used' (1#1 to 3" ) * a * 2 !

: Cla!! :@ a%plifier i! an a%plifier that operate! bet een the t o e3tre%e! defined forCla!! : and @ a%plifier!/ Class C l ess than "0% is used (0 to 1+ ) a * ! Cla!! C a%plifier! cond"ct le!! than =;> of the inp"t !ignal. allo ing it to reach G;>efficienc+ b"t re!"lting in high di!tortion at the o"tp"t/ Th"!. in a Cla!! C a%p. the o"tp"tc"rrent 'or &oltage) i! 5ero for %ore than =;> of the inp"t a&efor% c+cle/ So%eapplication!. !"ch a! %egaphone!. can tolerate the high di!tortion of Cla!! C a%p!/ Cla!!C a%p! can al!o be "!ed in t"ned R2 application!. !ince the di!tortion can be !ignificantl+red"ced b+ the t"ned load!/

Class D : cla!! D a%plifier i! a po er a%plifier ho!e po er de&ice! are operated in on0off %ode/The inp"t !ignal i! con&erted into a !e7"ence of p"l!e! ho!e a&erage i! directl+ proportional to the a%plit"de of the inp"t !ignal/ The fre7"enc+ of the p"l!e! i! t+picall+ten or %ore ti%e! the highe!t fre7"enc+ of intere!t in the inp"t !ignal/ The o"tp"t of thea%plifier goe! thro"gh a pa!!i&e filter to re%o&e "n anted !pectral co%ponent!. re!"ltingin an a%plified replica of the inp"t/ o er efficienc+ i! the %ain ad&antage of a cla!! Da%plifier/ Cla!! D a%plifier! ere idel+ "!ed to control %otor!. b"t the+ are al!o "!ed a!a"dio a%plifier!/

Class E/F

Cla!! E02 a%plifier! are highl+ efficient ! itching po er a%plifier! "!ed at radiofre7"encie!/ Cla!! E02 a%plifier! con!i!t of t o ba!ic part!6 1) a 9perfect9 ! itching de&icand $) an i%pedance net or* con!i!ting of re!i!ti&e and reacti&e co%ponent!/ The! itching de&ice i! 9on9 d"ring the 5ero-&oltage cro!!ing. and off d"ring the 5ero-c"rrencro!!ing. !"ch that it can not ha&e both c"rrent flo ing thro"gh it and a non-5ero &oltage

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acro!! it at the !a%e ti%e. thereb+ %ini%i5ing it! po er di!!ipation/ The i%pedancenet or*. on the other hand. i! !et "p !"ch that the 9i%aginar+ part9 of the i%pedance i!eli%inated thro"gh proper %atching of co%ple3 con,"gate! to attain re!onance. lea&ing behind onl+ it! 9real part/9 Th"!. a Cla!! E02 a%p i! &er+ efficient beca"!e po er lo!! onocc"r! in the real part 're!i!ti&e co%ponent) of the i%pedance net or*/ Cla!!e! E and 2

are di!ting"i!hed fro% each other b+ their re!onance topolog+/ There are !e&eral other cla!!e! of a%plifier! not di!c"!!ed in thi! article/

Negati&e 2eedbac*

Negati&e feedbac* i! "!ed in a%plifier! for a &ariet+ of rea!on!/ The ter% 9feedbac*9%ean! "!ing a fraction of the o"tp"t &oltage of the a%plifier a! inp"t or a! part of inp"t/Fhen the !ignal! at inp"t and o"tp"t are of oppo!ite pha!e 'i/e/. the+ are %irror-i%aged).then the feedbac* !ignal i! !aid to be negati&e/

Negati&e feedbac* !ignal! are !"btracted fro% the a%plifier9! inp"t !ignal'!)/ In effect.the+ red"ce the o&erall gain of the a%plifier/ If 4 i! the gain of the a%plifier ith nofeedbac* 'al!o *no n a! the 9open-loop gain9). and n i! the feedbac* fraction 'or loopgain) !"ch that Vo"t0n i! fed bac* to the inp"t of the a%plifier. then the gain of thea%plifier hen negati&e feedbac* i! applied 'clo!ed-loop gain) i! a! follo !6 Clo!ed-Loop 4ain ( 4 0 '1 < 40n)/ 2or e3a%ple. if the open-loop gain 4 ( 1;; and n ( 1; '!o that 101; of the o"tp"t &oltagei! fed bac*). then the clo!ed-loop gain i! 1;;0'1


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2ig"re 1a/ 2eedbac* in Sh"ntith the Inp"t Signal

2ig"re 1b/ 2eedbac* in Serie! ithInp"t 'thro"gh the e%itter of fir!t

tran!i!tor) The o"tp"t re!i!tance %a+ al!o be affected b+ a feedbac* net or*. altho"gh to a le!!ere3tent than the inp"t re!i!tance/ Connecting the feedbac* circ"it in !erie! ith the o"tp"tload increa!e! the a%plifier9! o"tp"t re!i!tance hile connecting it in parallel ith theo"tp"t load ill decrea!e the a%plifier9! o"tp"t re!i!tance

Lo - a!! 2ilter!

: Lo - a!! 2ilter i! a circ"it that onl+ allo ! lo -fre7"enc+ !ignal! to pa!!. andatten"ate! or red"ce! !ignal! ho!e fre7"encie! e3ceed it! c"t-off fre7"enc+/ It i! al!oreferred to a! a 9high-c"t filter9 or. hen "!ed in a"dio application!. a! a 9treble-c"t filter9/One co%%on application of lo -pa!! filter! i! for dri&ing !"b oofer! '!pea*er! de!ignedfor ba!! !o"nd!) and other lo"d!pea*er! that don9t efficientl+ broadca!t !o"nd! of high pitche!/ The lo -pa!! filter i! the oppo!ite of thehigh-pa!! filter /

:n ideal lo -pa!! filter i! one that co%pletel+ bloc*! all fre7"encie! abo&e a gi&enfre7"enc+. hile allo ing all tho!e ith lo er fre7"encie! to pa!! "nchanged/ Of co"r!e.an ideal lo -pa!! filter doe!n9t e3i!t in the real orld. !o a+! to 7"antif+ or de!cribe theeffecti&ene!! and efficienc+ of a lo -pa!! filter ha&e been de&i!ed/

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2ig"re 1/ Lo - a!! 2ilter! The 7"alit+ of a lo -pa!! filter %a+ be e3pre!!ed in ter%! of it!n-order / :n n-order filterred"ce! the !ignal !trength b+n d@ for e&er+ octa&e increa!e in fre7"enc+. i/e/. e&er+ti%e the fre7"enc+ do"ble!/ Th"!. afir!t-order lo -pa!! filter 'n(1) ill red"ce the !ignal !trength b+ d@ e&er+ ti%ethe fre7"enc+ do"ble!/ ?athe%aticall+. - d@ ( $; log $0 1. hich +ield! $0 1 ( ;/=;1/Thi! %ean! that a fir!t-order filter red"ce! the !trength of the !ignal b+ abo"t =;> e&er+ti%e the fre7"enc+ do"ble!/ :! f"rther ill"!tration. a!econd-order lo -pa!! filter 'n($) ill red"ce the !ignal !trength b+ 1$ d@ e&er+ ti%e the fre7"enc+ of the !ignal do"ble! '-1$ d@ per octa&e)/ Th"!. a!econd-order lo -pa!! filter ill red"ce a !ignal to ,"!t 108 it! original le&el e&er+ ti%e it!fre7"enc+ increa!e! b+ an octa&e/ Note that in each of the lo -pa!! filter! !ho n abo&e. the ind"ctor! are in !erie! ith theinp"t hile the capacitor! are in !h"nt ith the inp"t/ Thi! i! beca"!e the reactance L ofan ind"ctor increa!e! ith the !ignal fre7"enc+. i/e/. L ( $ fL. hile the reactance C ofa capacitor decrea!e! ith the !ignal fre7"enc+. i/e/. C ( 1 0 $ fC/ Th"! in the!e lo - pa!! filter!. the ind"ctor! re!i!t the pa!!ing of an ac !ignal a! the fre7"enc+ increa!e!.

hile the capacitor! !h"nt the% to ard! the gro"nd a! the fre7"enc+ increa!e!/ Eithera+. the effect i! to atten"ate the !ignal a! fre7"enc+ increa!e!/

The follo ing e7"ation! appl+ to the lo -pa!! filter! in 2ig"re 1 abo&e61) L ( o 0 f$) C ( 1 0 ' f o)

) o ( !7rt'L0C)8) f ( 1 0 ' !7rt'LC))

here o i! the line i%pedance and f i! the c"t-off fre7"enc+ of the filter/

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High- a!! 2ilter!: High- a!! 2ilter i! a circ"it that onl+ allo ! high-fre7"enc+ !ignal! to pa!!. andatten"ate! or red"ce! !ignal! ho!e fre7"encie! are belo it! c"t-off fre7"enc+/ It i! al!oreferred to a! a 9lo -c"t filter9 or. hen "!ed in a"dio application!. a! a 9ba!!-c"t filter9 or9r"%ble filter9/ One co%%on application of high-pa!! filter! i! for dri&ing t eeter!'!pea*er! de!igned for high-pitch !o"nd!). !o a! to bloc* lo -fre7"enc+ !ignal! that caninterfere ith or e&en da%age the t eeter/ The high-pa!! filter i! the oppo!ite of thelo - pa!! filter /

:n ideal high-pa!! filter i! one that co%pletel+ bloc*! all fre7"encie! belo a gi&enfre7"enc+. hile allo ing all tho!e ith higher fre7"encie! to pa!! "nchanged/ Of co"r!e.an ideal high-pa!! filter doe!n9t e3i!t. !o in the real orld. the effecti&ene!! and efficienc+of a high-pa!! filter i! de!cribed i! ter%! of the le&el of atten"ation of !ignal! ithfre7"encie! belo a c"t-off fre7"enc+/ The c"t-off fre7"enc+ of a high-pa!! filter i! thefre7"enc+ at hich the o"tp"t &oltage e7"al! ;/ > of the inp"t &oltage/ 2ig"re 1 !ho ! !o%e co%%on i%ple%entation! of high-pa!! filter!/ Note that in each ofthe high-pa!! filter! !ho n abo&e. the ind"ctor! are in !h"nt ith the inp"t hile thecapacitor! are in !erie! ith the inp"t/ Thi! i! beca"!e the reactance L of an ind"ctor

increa!e! ith the !ignal fre7"enc+. i/e/. L ( $ fL. hile the reactance C of a capacitordecrea!e! ith the !ignal fre7"enc+. i/e/. C ( 1 0 $ fC/ Th"! in the!e high-pa!! filter!.the capacitor! re!i!t the pa!!ing of an ac !ignal a! the fre7"enc+ decrea!e!. hile theind"ctor! !h"nt the% to ard! the gro"nd a! the fre7"enc+ decrea!e!/ Either a+. theeffect i! to atten"ate the !ignal a! fre7"enc+ decrea!e!/

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2ig"re 1/ High- a!! 2ilter!

The follo ing e7"ation! appl+ to the high-pa!! filter! in 2ig"re 1 abo&e61) L ( o 0 8 f$) C ( 1 0 '8 f o)

) o ( !7rt'L0C)8) f ( 1 0 '8 !7rt'LC))

here o i! the line i%pedance and f i! the c"t-off fre7"enc+ of the filter/

The @ipolar Tran!i!tor a! a S itch: ! itch i! a de&ice that i! "!ed to 9open9 or 9clo!e9 a circ"it/ Opening a circ"it %ean!creating a brea* in the circ"it. pre&enting c"rrent flo and th"!. t"rning it 9off9/ Clo!ing acirc"it. on the other. %ean! co%pleting the circ"it path. thereb+ allo ing c"rrent to floaro"nd it and th"!. t"rning it 9on9/

The bipolar tran!i!tor . hether N N or N . %a+ be "!ed a! a ! itch/ Recall that the bipolar tran!i!tor ha! three region! of operation6 the c"t-off region. the linear or acti&e

region. and the !at"ration region/ Fhen "!ed a! a ! itch. the bipolar tran!i!tor i! operatedin the c"t-off region 'the region herein the tran!i!tor i! not cond"cting. and therefore%a*e! the circ"it 9open9) and !at"ration region 'the region herein the tran!i!tor i! in f"llcond"ction. thereb+ clo!ing the circ"it)/ The bipolar tran!i!tor i! a good ! itch beca"!e of it! largetran!cond"ctance 4%. ith4%( Ic0Vbe here Ic i! the collector-to-e%itter 'o"tp"t) c"rrent and Vbe i! the ba!e-e%itter'inp"t) &oltage/ It! high 4% allo ! large collector-to-e%itter c"rrent! to be ea!il+

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achie&ed if !"fficient e3citation i! applied at the ba!e/

To ill"!trate thi!. the !i%ple!t a+ to "!e an N N bipolar tran!i!tor a! a ! itch i! to in!ertthe load bet een the po!iti&e !"ppl+ and it! collector. ith the e%itter ter%inal gro"nded'a! !ho n in 2ig"re 1)/ :ppl+ing no &oltage at the ba!e of the tran!i!tor ill p"t it in the

c"t-off region. pre&enting c"rrent fro% flo ing thro"gh it and thro"gh the load. hich i! are!i!tor in thi! e3a%ple/ In thi! !tate. the load i! 9off9/

2ig"re 1/ : Si%ple S itch U!ing an N NTran!i!tor

:ppl+ing eno"gh &oltage at the ba!e of the tran!i!tor ill ca"!e it to!at"rate and beco%ef"ll+ cond"cti&e. effecti&el+ p"lling the collector of the tran!i!tor to near gro"nd/ Thi!ca"!e! a collector-to-e%itter c"rrent to flo thro"gh the load that9! li%ited onl+ b+ the

i%pedance of the load/ In thi! !tate. the load i! 9on9/ One li%itation of thi! !i%ple de!ign i! that the ! itch-off ti%e of the tran!i!tor i! !lo erthan it! ! itch-on ti%e if the load i! a re!i!tor/ Thi! i! beca"!e of the !tra+ capacitanceacro!! the collector of the tran!i!tor and gro"nd. hich need! to charge thro"gh the loadre!i!tor d"ring ! itch-off/ On the other hand. thi! !tra+ capacitance i! ea!il+ di!charged togro"nd b+ the large collector c"rrent flo hen the tran!i!tor i! ! itched on/ There are. of co"r!e. other better de!ign! for "!ing the bipolar tran!i!tor a! a ! itch/

S itching Circ"it! U!ing @ipolar Tran!i!tor! :! di!c"!!ed in another article. the bipolar tran!i!tor i! a good ! itching de&ice beca"!e of

it! largetran!cond"ctance 4%/ The !a%e article !ho ed the !i%ple circ"it in 2ig"re 1 belo . herein a !ingle N N tran!i!tor i! "!ed a! a ! itch for energi5ing or po ering offthe load re!i!tor connected bet een the collector and the po!iti&e !"ppl+/

One proble% ith the !i%ple ! itch circ"it in 2ig"re 1 i! the fact that a !tra+ capacitancee3i!t! bet een the tran!i!tor9! collector and it! gro"nded e%itter. !"ch that the ! itch-off

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ti%e of the tran!i!tor i! !lo er than it! ! itch-on ti%e/ Thi! i! beca"!e d"ring ! itch-off.thi! !tra+ capacitance ha! to charge fir!t thro"gh the load re!i!tor before the load c"rrent!top!/ D"ring ! itch-on. on the other hand. thi! !tra+ capacitance need! to di!charge togro"nd. hich i! ea!il+ acco%pli!hed b+ the cond"cting tran!i!tor/ The !lo er charging "pof the !tra+ capacitance co%pared to it! 7"ic* di!charging i! the rea!on h+ the ! itch-off

of 2ig"re 19! circ"it i! !lo er than it! ! itch-on/ The circ"it in 2ig"re $ addre!!e! the li%itation of the circ"it in 2ig"re 1/ T o o"tp"ttran!i!tor! are "!ed in thi! circ"it. dri&en b+ a !ingle inp"t tran!i!tor/ The o"tp"t of thi!circ"it i! ta*en fro% the collector of the lo er tran!i!tor/ J"!t li*e the circ"it in 2ig"re 1.thi! circ"it i! an in&erting circ"it. i/e/. the o"tp"t !ignal ha! a pha!e that9! oppo!ite that ofthe inp"t !ignal/ Th"!. the o"tp"t i! lo if the inp"t i! high and the o"tp"t i! high if theinp"t i! lo /

2ig"re 1/ : !i%ple ! itch"!ing an N N tran!i!tor

2ig"re $/ : circ"it ith t oo"tp"t tran!i!tor!. allo inge7"all+ rapid ! itch-off and! itch-on

If the inp"t i! high. the "pper o"tp"t tran!i!tor goe! into c"t-off beca"!e it! ba!e &oltage i! p"lled do n b+ the cond"cting inp"t tran!i!tor/ ?ean hile. the lo er o"tp"t tran!i!tor!at"rate! beca"!e the cond"cting inp"t tran!i!tor i! !"ppl+ing it! ba!e ith a higherc"rrent/ S"ch condition! i%%ediatel+ p"ll! do n the collector of the lo er o"tp"ttran!i!tor to al%o!t gro"nd le&el. i/e/. the o"tp"t goe! 9lo 9/ On the other hand. if the inp"t i! lo . the inp"t tran!i!tor !top! cond"cting. ca"!ing the&oltage at the ba!e of the "pper o"tp"t tran!i!tor to be p"lled "p b+ the po!iti&e !"ppl+.thereb+ t"rning it on/ ?ean hile. the non-cond"cting inp"t tran!i!tor pre&ent! the ba!e ofthe lo er o"tp"t tran!i!tor fro% recei&ing an+ c"rrent. dri&ing it into c"t-off/ Fith thelo er o"tp"t tran!i!tor in c"t-off and the "pper o"tp"t tran!i!tor cond"cting. the o"tp"t ofthe circ"it i! p"lled "p to ard! the po!iti&e !"ppl+. i/e/. the o"tp"t goe! 9high/9

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The circ"it in 2ig"re $ allo ! the o"tp"t to ! itch off a! fa!t a! it! ! itch-on. !ince thecond"cting lo er o"tp"t tran!i!tor i%%ediatel+ p"ll! the o"tp"t to gro"nd d"ring ! itch-off/

The Darlington air TheDarlington pair i! ba!icall+ a co%bination of t o bipolar tran!i!tor! connected a!!ho n in 2ig"re 1 belo / Thi! circ"it i! "!ed fora%plif+ing c"rrent!. i/e/. the a%plifiedc"rrent fro% the fir!t tran!i!tor i! f"rther a%plified b+ the !econd tran!i!tor/ Needle!! to!a+. thi! tran!i!tor co%bination e3hibit! a %"ch higher c"rrent gain than if onl+ onetran!i!tor ere "!ed/

The o&erall c"rrent gain of the Darlington pair i! ,"!t e7"al to the prod"ct of the t o

indi&id"al c"rrent gain! of the tran!i!tor!/ Th"!. if h2E1 and h2E$ are the c"rrent gain! oftran!i!tor! 1 and $. re!pecti&el+. the o&er-all c"rrent gain h2E if the+ are for%ed a! aDarlington pair ill beh2E ( h2E1 3 h2E$/ The &er+ high c"rrent gain 'e/g/. 1;;;;) of aDarlington pair %ean! that onl+ a tin+ a%o"nt of ba!e c"rrent i! needed to %a*e the pair! itch on/

2ig"re 1/ The Darlington air Circ"it The Darlington circ"it i! na%ed after it! in&entor. @ell Lab! engineer Sidne+ Darlington/The concept of placing t o or three tran!i!tor! on a !ingle chip a! patented b+ hi%. b"t p"tting an arbitrar+ n"%ber of tran!i!tor! on a !ingle chip. hich o"ld enco%pa!! all%odernIC9!. a! not co&ered b+ hi! patent/ : Darlington pair beha&e! ,"!t li*e a !ingle tran!i!tor ith a &er+ high c"rrent gain. i/e/. itcan al!o be %odeled a! ha&ing the three ter%inal! of a t+pical tran!i!tor - the ba!e. thee%itter. and the collector/ : !ingle tran!i!tor re7"ire! ,"!t ;/ V acro!! it! ba!e-e%itterter%inal to t"rn on/ : Darlington pair. on the other hand. re7"ire! do"ble that a%o"nt. or1/8 V. !ince it! inp"t ba!icall+ ha! t o ba!e-e%itter ,"nction! in !erie! 'refer to 2ig"re 1)/If Vbe1 and Vbe$ are the ba!e-e%itter &oltage! needed to t"rn on the fir!t and !econdtran!i!tor! of the Darlington pair. re!pecti&el+. then the Vbe re7"ired to t"rn on the pair i!Vbe ( Vbe1 < Vbe$/

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Darlington pair! pac*aged a! a !ingle tran!i!tor are alread+ &er+ co%%on in the%ar*etplace/ Ho e&er. thi! ha! not di%ini!hed the practice of for%ing Darlington pair!fro% t o di!crete tran!i!tor!. !ince thi! offer! %ore fle3ibilit+/ The load c"rrent ill becarried b+ the !econd tran!i!tor. !o it ha! to ha&e a higher po er rating than the fir!t

tran!i!tor/ The %a3i%"% load c"rrent of the Darlington pair i! the %a3i%"% c"rrent thatthe !econd tran!i!tor can carr+/

The Long-Tailed air 'LT ) Circ"it

TheLong-Tailed air 'LT ) i! a circ"it that con!i!t! of t o bipolar tran!i!tor! ho!ee%itter! are connected together. a! !ho n in 2ig"re 1/ 2"rther%ore. the inp"t of the circ"iti! applied acro!! the ba!e! of the t o tran!i!tor!. hile the o"tp"t i! "!"all+ ta*en fro%

acro!! their collector!/ The long-tailed pair circ"it i! a &er+ idel+ "!ed circ"it in linearapplication!. %ainl+ a! adifference a%plifier / 2ield-Effect Tran!i!tor! '2ET9!) and&ac""% t"be! %a+ al!o be "!ed in i%ple%enting long-tailed pair!. herein the 2ET!o"rce! and &ac""% t"be cathode! are the ter%inal! connected together. re!pecti&el+/

The ter% 9long-tail9 ca%e fro% the fact that the large re!i!tor connecting the e%itter! of ttran!i!tor! to gro"nd or a po er !"ppl+ re!e%ble! a long tail/ In 2ig"re 1. herein N Ntran!i!tor! are "!ed to for% the pair. thi! re!i!tor i! tied to gro"nd/ The long tail act"all+f"nction! a! a c"rrent !o"rce. and %a+ in fact be replaced a %ore elaborate 9acti&e9 c"rren!o"rce circ"it/

2ig"re 1/ The Long-Tailed air'LT ) Circ"it

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The long-tailed pair circ"it i! often "!ed for a%plif+ing an+ difference bet een the !ignal!applied at the ba!e of each tran!i!tor/ If the t o tran!i!tor! "!ed are identical and balanced. a co%%on-%ode !ignal 'i/e/. a !ignal applied in the !a%e pha!e to both inp"t!)applied to the ba!e! of the tran!i!tor! ill not ca"!e an+ !ignificant difference! bet een the

&oltage! at the collector! of the t o tran!i!tor!/ In fact. an+ difference o"ld onl+ be d"eto a lac* of balance bet een the tran!i!tor!/ Th"!. the o"tp"t of thi! circ"it ' hich i! ta*enacro!! the collector!) for a co%%on-%ode !ignal o"ld ideall+ be 5ero/ On the other hand. e&en a %in"te difference bet een the ba!e !ignal! ill be a%plifiedcon!iderabl+ b+ the tran!i!tor!. and ill be reflected at the o"tp"t a! an a%plified &er!ionof the difference bet een the !ignal!/ Th"!. the differential gain of thi! circ"it i! &er+high. herea! it! co%%on-%ode gain i! &er+ lo / Thi! i! h+ thi! circ"it i! e3ten!i&el+"!ed in the inp"t circ"itrie! of operational a%plifier!/

Operational :%plifier! 'Op-:%p!) :n Operational :%plifier . or Op :%p. i! a d"al-inp"t. !ingle-o"tp"t linear a%plifier thate3hibit! a high open-loop gain. high inp"t re!i!tance!. and a lo o"tp"t re!i!tance/ One ofthe inp"t! of an operational a%plifier a%p i! non-in&erting hile the other i! in&erting/The o"tp"t Vo"t of an operational a%plifier itho"t feedbac* 'al!o *no n a! open-loop) i!gi&en b+ the for%"la6 Vo"t ( :'Vp-Vn) here : i! the open-loop gain of the op a%p. Vpi! the &oltage at the non-in&erting inp"t. and Vn i! the &oltage at the in&erting inp"t/ Theopen-loop gain of a t+pical op a%p i! in the range of 1;=-1; /

The operational a%plifier got it! na%e fro% the fact that it can be config"red to perfor%%an+ different %athe%atical operation!/ Depending on it! feedbac* circ"it and bia!ing. aop a%p can be %ade to add. !"btract. %"ltipl+. di&ide. negate. and. intere!tingl+. e&en perfor% calc"l"! operation! !"ch a! differentiation and integration/ Of co"r!e. a!ide fro%the!e operation!. op a%p! are al!o fo"nd in a &er+ large n"%ber of application!/ In fact.%an+ con!ider the op a%p a! the fo"ndation of %an+ analog !e%icond"ctor prod"ct!toda+/ @eca"!e of the &er+ high re!i!tance e3hibited b+ the inp"t! of an op a%p. the c"rrent!flo ing thro"gh the% are &er+ !%all/ The c"rrent flo ing in or o"t of an op a%p9! inp"t pin. *no n a! inp"t bia! c"rrent. i! ba!icall+ ,"!t lea*age c"rrent at the ba!e or gate of theinp"t tran!i!tor of that inp"t. hich i! h+ it i! &er+ !%all/ Fhen !ol&ing &oltage0c"rrente7"ation! for op a%p circ"it!. the inp"t c"rrent! are "!"all+ a!!"%ed to be 5ero/ 2or %o!tof the co%%onl+-"!ed op-a%p circ"it!. thi! %ean! that the total o"tp"t c"rrent of the opa%p i! flo ing thro"gh the feedbac* circ"it bet een the o"tp"t and the in&erting inp"t 'thefeedbac* i! "!"all+ connected to the in&erting inp"t for operation !tabilit+)/

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:! the %ain path for an op a%p9! o"tp"t c"rrent. the feedbac* circ"it "!ed in an op a%plargel+ deter%ine! ho the op a%p ill f"nction/ There are %an+ a+! to operate an opa%p. b"t one co%%onl+-"!ed ba!ic config"ration i! to6 1) pro&ide it ith balanced !"ppl+&oltage! '!a+.


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In!tr"%entation :%plifier! 'In-:%p!)

:n In!tr"%entation :%plifier . or In-:%p. i! a clo!ed-loop. differential-inp"t a%plifier

ith an o"tp"t that i! !ingle-ended ith re!pect to a reference ter%inal/ It ha! clo!el+-%atched inp"t re!i!tance! that are &er+ high in &al"e. t+picall+ greater than 1;G oh%!/ Li*eanoperational a%plifier . an in!tr"%entation a%plifier %"!t ha&e &er+ lo inp"t bia!c"rrent! 'c"rrent! flo ing in or o"t the inp"t ter%inal!. t+picall+ in the order of !e&eral n:for in a%p!). and a &er+ lo o"tp"t i%pedance 'no%inall+ a fe %illioh%! at lofre7"encie!)/

The %ain difference bet een an in!tr"%entation a%plifier and an operational a%plifier i!the fact that an op a%p i! an open-loop de&ice. herea! an in-a%p co%e! ith a pre!etinternal feedbac* re!i!tor net or* that i! i!olated fro% it! inp"t ter%inal!/

@eca"!e it i! an open-loop de&ice. an op a%p9! f"nction and gain i! !et b+ pro&iding it e3ternal co%ponent! that generall+ con!tit"te a feedbac* circ"it bet een it! o"tp"t and it!in&erting inp"t/ On the other hand. the gain of an in-a%p. hich i! "!ed pri%aril+ a! ana%plifier of lo -le&el !ignal! in noi!+ en&iron%ent!. i! either %an"fact"rer-pre!et or %a+ be !et b+ the "!er "!ing an e3ternal gain re!i!tor or b+ %anip"lating internal re!i!tor! &ia!o%e of the in-a%p9! pin!/

Of co"r!e. an operation a%plifier %a+ be "tili5ed a! an in!tr"%entation a%plifier/ Thi! i!done b+ config"ring it a! a differential a%plifier or !"btractor. a! !ho n in 2ig"re 1a. the

circ"it of hich gi&e! an o"tp"t &oltage Vo that i! proportional to the difference bet eenthe inp"t &oltage!. or Vo ( Rf0Ri 'V$-V1)/ Thi! e7"ation %a+ be deri&ed a! follo !61) Vo ( -If Rf < Vi here Vi i! the &oltage at either inp"t of the op a%p#$) b"t If ( 'V1-Vo)0'Ri


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2ig"re 1/ a) an operational a%plifier config"red a! a differential a%plifier to !er&e a! a!i%ple in-a%p 'left)# b) an in-a%p con!i!ting of three ' ) op a%p! 'right)

ropertie! that define a high 7"alit+ in!tr"%entation a%plifier are6 1) high co%%on %odere,ection ratio# $) lo off!et &oltage and off!et &oltage drift# ) lo inp"t bia! and inp"t

off!et c"rrent!# 8) ell-%atched and high-&al"e inp"t i%pedance!# =) lo noi!e# ) lonon-linearit+# ) !i%ple gain !election# and ) ade7"ate band idth/

E3a%ple! of application! here in-a%p! %a+ be "!ed incl"de6 1) data ac7"i!ition fro%lo o"tp"t tran!d"cer!# $) %edical in!tr"%entation# ) c"rrent0&oltage %onitoring# 8)a"dio application! in&ol&ing ea* a"dio !ignal! or noi!+ en&iron%ent!# =) high-!peed!ignal conditioning for &ideo data ac7"i!ition and i%aging# and ) high fre7"enc+ !ignala%plification in cable R2 !+!te%!/

Voltage Reg"lator!

Voltage Reg"lator!. al!o *no n a! &oltage !tabili5er!. are circ"it! that o"tp"t a con!tantand !table DC &oltage at a !pecified le&el. de!pite fl"ct"ation! in it! inp"t &oltage or&ariation! in it! load/ Voltage reg"lator IC9! ha&e alread+ beco%e a&ailable in !o %an+for%! and characteri!tic! that the+9&e &irt"all+ eli%inated the need to b"ild &oltagereg"lating circ"it! fro% di!crete co%ponent!/ 2actor! that !p"rred the gro th of the &oltage reg"lator IC b"!ine!! incl"de6 1) ea!e ith

hich 5ener diode! and balanced a%plifier! can be b"ilt into IC9!# $) i%pro&ed IC heatdi!!ipation capabilitie!# ) ad&ance! in o&erload protection techni7"e!# and of co"r!e. 8)high de%and for &oltage reg"lator! in al%o!t all field! of the electronic! ind"!tr+.

e!peciall+ in po er !"ppl+ application!/

I%portant con!ideration! hen !electing a &oltage reg"lator incl"de6 1) the de!ired o"tp"t&oltage le&el and it! reg"lation capabilit+# $) the o"tp"t c"rrent capacit+# ) the applicabinp"t &oltage!# 8) con&er!ion efficienc+ ' o"t0 in)# =) the tran!ient re!pon!e ti%e# ) eof "!e# and if applicable. ) the abilit+ to !tep-do n or !tep-"p o"tp"t &oltage!/ In ! itch-%ode reg"lator!. the ! itching fre7"enc+ i! al!o a con!ideration/

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There are !e&eral t+pe! of &oltage reg"lator!. hich %a+ be cla!!ified in ter%! of ho theoperate or hat t+pe of reg"lation the+ offer/ The %o!t co%%on reg"lator IC i! the!tandard linear reg"lator/ : t+pical linear &oltage reg"lator operate! b+ forcing a fi3ed&oltage at the o"tp"t thro"gh a &oltage-controlled c"rrent !o"rce/ It ha! a feedbac*

%echani!% that contin"o"!l+ ad,"!t! the c"rrent !o"rce o"tp"t ba!ed on the le&el of theo"tp"t &oltage/ : drop in &oltage o"ld e3cite the c"rrent !o"rce into deli&ering %orec"rrent to the load to %aintain the o"tp"t &oltage/ Th"!. the capacit+ of thi! c"rrent !o"rcei! generall+ the li%iting factor for the %a3i%"% load c"rrent that the linear reg"lator candeli&er hile %aintaining the re7"ired o"tp"t le&el/ The a%o"nt of ti%e needed for theo"tp"t to ad,"!t to a change in the inp"t or load i! the tran!ient re!pon!e ti%e of thereg"lator/ The feedbac* loop "!ed b+ linear reg"lator! need !o%e for% of co%pen!ation for !tabilit+In %o!t linear reg"lator IC9!. the re7"ired feedbac* loop co%pen!ation i! alread+ b"ilt intothe circ"it. thereb+ re7"iring no e3ternal co%ponent! for thi! p"rpo!e/ Ho e&er. !o%e

reg"lator IC9!. li*e the lo -dropo"t one!. do re7"ire that a capacitor be connected bet eenthe o"tp"t and gro"nd to en!"re !tabilit+/ The %ain di!ad&antage of linear reg"lator! i!their lo efficienc+. !ince the+ are con!tantl+ cond"cting/

The ! itching &oltage reg"lator i! another t+pe of reg"lator IC/ It differ! fro% the linearreg"lator in the !en!e that it e%plo+! p"l!e idth %od"lation ' F?) to reg"late it!o"tp"t/ The o"tp"t i! controlled b+ c"rrent that i! ! itched at a fi3ed fre7"enc+ rangingfro% a fe H5 to a fe *H5 b"t ith &ar+ing d"t+ c+cle/ The d"t+ c+cle of the p"l!e!increa!e if the o"tp"t of the reg"lator need! to !"ppl+ %ore load c"rrent to %aintain theo"tp"t &oltage and decrea!e! if the o"tp"t need! to be red"ced/ S itching reg"lator! are%ore efficient than linear reg"lator! beca"!e the+ onl+ !"ppl+ po er hen nece!!ar+/Co%ple3it+. o"tp"t ripple!. and li%ited c"rrent capacit+ are the di!ad&antage! of ! itchinreg"lator!/ There i! al!o a gro"p of reg"lator IC9! *no n a! Lo Drop-o"t 'LDO) reg"lator!/ Thedrop-o"t &oltage i! the %ini%"% &oltage acro!! the reg"lator that9! re7"ired to %aintainthe o"tp"t &oltage at the correct le&el/ The lo er the drop-o"t &oltage. the le!! po er i!di!!ipated internall+ ithin the reg"lator. the higher i! the reg"lation efficienc+/ In LDOreg"lator!. the drop-o"t &oltage i! t+picall+ ,"!t abo"t ;/ V/ E&en at %a3i%"% c"rrent.the drop-o"t &oltage increa!e! to ,"!t abo"t ;/ -;/ V/

E3a%ple! of application! of reg"lator IC9! incl"de the follo ing6 1) reg"lated po er!"pplie!# $) data con&er!ion ':DC0D:C) circ"it!# ) !en!or and triggering !+!te%!# 8)DC-to-DC &oltage con&erter!# =) %ea!"re%ent and in!tr"%entation !+!te%!# ) %otorcontrol# and ) batter+ charging/

:nalog S itche!

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:n analog ! itch i! a !olid-!t

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