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Title:
METHOD AND APPARATUS FOR MEASUREMENT OF ELECTRICAL RESISTANCE
Document Type and Number:
WIPO Patent Application WO/2007/082125
Kind Code:
A3
Abstract:
An electronic circuit and method to determine a resistance value of a resistive element (201). The circuit includes a current source (209) coupled in series with the resistive element (201). The current source (209) is configured to force a predetermined value of current through the resistive element (201) and includes a transconducting device (207) coupled to the current source (209). The transconducting device (207) is configured to sense a voltage across the resistive element (201) and transform the voltage into an output current of the transconducting device (207) such that the output current is not dependent upon any other terminal voltages of the transconducting device.

Inventors:
BORDELON TERRY JAMES (US)
Application Number:
PCT/US2007/060077
Publication Date:
May 29, 2008
Filing Date:
January 04, 2007
Export Citation:
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Assignee:
STRATOSPHERE SOLUTIONS INC (US)
BORDELON TERRY JAMES (US)
International Classes:
G01R25/00
Foreign References:
US6795783B22004-09-21
US5552729A1996-09-03
US6977510B12005-12-20
Attorney, Agent or Firm:
SCHNECK, Thomas (P.O. Box 2-ESan Jose, CA, US)
Download PDF:
Claims:

1; An e ' kijtr όiώc ckcuit : : : tό detexmiϊiό : a resistance valne-of a :; resϊstϊtfe ': ..element:, the circuit .comprising:: a. cπrreiit source coupled in-sfeαies with, tile resistive eferneήt,, the 5 mirr.eήt source cdufigured.. : t& Ibi-Ge-a.pr'edeter.miπ.θ.d. value of current tliroKgh the ^resistive; element; aiid. a : transGθiι<iuctIn;g devieό;Gθ.ιi:pled.to the- curreiϊt source: εtήά : GόixSgιu'ed to s:e:Bδθ ' a ; γαiϊagi3 across the-.resistive element;, felαa; traiisconducting &viee;£iiii;hep cojiFiguresd to tmiisforih. fcMe vdkage iiϊtoaϊi. 10. outpitit current of the: .tr . an&cόn&.UGting ^ d.e%'Ice J: the outp.ut cuiTent not being dependeiit; upon san^ ath&x ierminal ; voltages -of the transcond^cfiiig deyie^.,

2. The electronic eircπit oiclaim: 1 wherein the- transfcondπcting device IB a- transi^toi'.

:S. The δiectroiϊic circuit αf-elaim : U wherein the transistor, is a lPMOSFET ..device.

.4. An eiectroftic circuit 4Q destermme^a resistance value of a: £ϊxs%: resistive.. 0 eleme.rit,. : th.e ; -circuit pα^β ' ii^iatig: a Erst-current source coupled in series with ' the first resistive eJetoent / thej.&'.st curfent spur-ee coiifigtii'ed to force a. first ' piledMermiαed. value of current through: the fiϊώt xesistiv«: : element; a .secόnά resistive 'element coupled in series -with the : first resistive 5 .element and forming a node; a secϋiϊdciuiTent source; δθtι|>l : e.d : to .the: fii-s.t cxϊrrent source;.. such that the Srst resistiye element is c.o.uple:d : therebetween, the secpnd. Qurϊeήt s:ourqe ; fethei' eάύpleά.m-s^riέs ' with the secGnd resistive" element at the .node, the second -current somxe configured to force a seeσnd 0 predete.i'mined value , qf-.cαrrentintό th& node; ;ψ.xιά.

- W-

a-traii^c.θϊiduc.tiϊig device sampled to. :: both: tfa.e.;j&r8t current soiirce aiid the.iirst&βd seeόnd resistiye elements, ;the ti'kiχscon,dύctmg : φyie!e configured to -gense.% first voltage across the- first ' arid second. resistive elements cpupied;iti : ;.series with, one another,, tlie rtr^nsconductirig device; .5 . further configured to teaήsfcif m. thφ. fi.ϊst voltage irϊto an. output current of "the :txεmsedtιduGtϊng deyicfeji -ύa$ ontpub -cwn∑&ni not .being dependent upon. .any other terrαinal ypjlages of the: traπscoHductingxlevicβ.-

5. The ..eiectroϊϊic cif euit: øf claim ..4 whexein a magnitude of the second ϊO predetermined value ,6£ current supplied by the seepnd ciUTejii; source is', established sύφ ' that "a second voltage gerieratediateiOss ih® sedoftd resistive eleinent is GortStaήt,.

6. The electronic: ciϊcύit":Qf : daαni.4 wherein the teaiiscόnducting de^icie is eϊ If transistor.

7. Tiie. electrci.ϊiϊG circuit; of claim β wherein the. tra-αsϊstcir is a PMDSEET device,.

2U 8. The electronic ciϊcuitiof eϊaina 7 ' wherein- the second resistive .ele.ment is emiEgύi'βd to shift a gate.4o-sqtirce : vpTt^β of:.the PMQSFEX device hy a, fixed aniount-

9, AIJ eleGti'.όnic circuit to. determine .a ϊ" ' esistaiice : -valύe of a resistive 2$ eleniQiit, the circuit : cρmj)rismg: : a current sotirce. coupled, to the •r ' es&tive ^i&M exit, the eiirretit source configured to force a predetermined value df current thfough the resistive element; a.first ty4M∞Mτtι.ctiήg de^dee coupled : to" the resistive eieriierit, the ZO. -.first transeoπdϋciirx| device xonfϊgui'ed to s^nse.-a Hrs.t voltage-, difference between a first node of the ϊre.siBtive element .ajicl a.iJefe . reii-cέ voltage,

fest traήseondiietiftg devϊ-ee Si£theϊ Gθiifigtιre.d.to transform €h© &st voltage -4i$fere.nee- into aϋi-st autjrat e:urre#i:;of the fest t|ans.coJDtdulitiϊig: deyice^such tMt tKe fϊϊsj dtitput cmφ&M is not dependent ' upon any όtheϊ terminal voltages of tke •transeQiϊ.duG.tm^.d.eykθ:; sm&

5 a second .transco^ductiiigrdeviGisJboupled 16. the resist-iye; eϊθiiiθhte.

' tlιe.#øύθB«J : t;ranBcόiiductiiig d0ιύ& coii gurisd to sense -a ,søϊX3iκi- voltage difference, between a-.secoBtd node of tke^e^Miye. elemeat ; aπd : ike refe3rap.ee yplbage , , tiie segαnd transepndtictihg deviee furtlier.configtHJed to transfoxm. the. second voltage: difibϊ- fence: iiάifco a second output cuiTfent of the ,0 secQnd .teansconducting device sivcli that the second output cuixeiit iέ.øt depeiidejGt i^iόn-aήy otliei ' teri^maϊ Voltages pf tlie traiisconduetiiig device ' .

IQ, The -electroiiic circuit of elajm.9 wker.ein. the i-eference : voltage is βstabllsfe.d. to be adjustable mjaagiύtiide thereby setting a magπitrαde of 5 the &st : and .second output cixεrents,

II.; The electronic cux:tiit/ό : f cla;im .9- wheα*eiϊϊ the .first and second transcαnducting 1 d ' exαeeis-are eaeli a transistor.,

0- 12. Th(2.:electiOnic ci-ccmt of ^ claim Xl wKerein the transistors are. ,:comϊ)ϊise.d:.of ' FMDgFET deyiees;.

13» A:iaethod for determining, a value of. electrical resistance, the metHpd. comprising:, 5 forciifg two or more values, σf kaόwn.:ctιϊrent through a resistor

Gl ider . fest to produce twQ . or . more. voltages: gen rated across the resistiar.; adding each of the two or. mote, voltages generated across the resistor to: an adjttstafeie constant voltage, ^lierebs^I^ 1 ' 0 ^ 116 ^ 1 ^ " ^ W P Q^m^M TOϊtage,sums;

- :2t -

sepai';ately -a|i . .p^kig eaeB..o£ : tlie voltage, sums to. andnp.Tiϊ of a. traπsconduGtiii g :dewice : gteiSemtiag a'.ciaiii'ent frσtd : t|ie tϊ'a.nscoMitάti^g'dievieβ baSed- on each of the applied - voltage. siimSj the/generated current ^.a^ying: g^.onerrtially 5 ' • with the iap.p.lied yoltagβ: S"uϊa;. measurmg; eath of ϊh.B value© of^ur^eat^goagirateXi By the- ti?ansco.n.4ucting device, at two or. more values of the Jαaow.n resistor cύim ή t; .and calculating tlie: value of electrical resistaftee ikόm ihβimsistoT under ϊ 0 - test . fi'pm : eaeli .of tϋe measured values. of current .generated by the tϊ^triscάiiduGtiiig device at two ^r.mpre. values όttJie ' kϊϊoWn: I'esistoi* GVLϊT&ϊLL

X4, The itijietko.d of ύeam .13 wiieϊem δalculatϊiig Um value of elecfeical 15 resistance, ineludes determiniiig a .difference in t : he- : iixe:a : sni ! e;d valttes of ptitgiύt current.

15.. 3Phe method, of. claim IB -wherein o.alcxiiating the- Value of electrical ' $øijβ&rCcύ furthδririeiudeφ sc.aliiig; eaeh o£ the Measured values -ό£ current; 20

16, Th^: ,m.ethqd. of. claim , 13: whereήi calculating iK& value- oϊ elόqtrical . resistarie&is iiidepehdent of an aBsoitate. magiiittKie of any of -thei valtte≤ of generated .tX'a^scoB^iiGting'.deλαce eurrent,.

25 17- The method . of plaim IB farther comprising ^selectmg a transcpnductiiig- device that has aii exponential tr^iϊsfer fttjicttbii of applied voltage to generated current.

Description:

Bescmpfcipii

METHOD ANfi APPAϊt&TϋS FdE MEASXJREMENT '

5

TE&HMIGAL FIELD

[00.01] TM; present, inveiltiøii is. related generally- to electronic testing. Mot e. specifically, tϋe. present invention ϊs ielated to a method and apparatus for acQura±e mie-a : siuirøan^|s;of ' S-n^-i*e'aiδtance values.

BACKGROUND

[0002| Coiάto.pώ metHodS to " ttt64sώ*.ό- an electrical resistanee jόf &n . electtica-Iiy conductiiig eieϊtϊeλt; are.: (I) applying; ør forcing, a Mown eoαstα.πt;yoltage ac-ross the twp terniinals comprising tiie i*esiatwe;efeiB:e.iit 15 an4,me;a^ϊiiig;t]ie re&uϊtiiig ^lecfcsϊc : c.urϊe3i.t; and (2) forciαig a kjϊoλyii . , constant .current througli -tke: rsξvsiativQ elenaent. mid m©aS"ul'iήg a resαlting vόl|.agβ,$røp across- the elenien ' t'?. terminals, ^Dhe. xesistance4s, thiw de&αed as tke ratio o£wltag&..to cwrreήt inxder static (non-tihi^-vatying^ conditions,

2Q røθ.03 ' 1 Any. additional uαikiloWn.. resistance (e.g., wiring :Qϊ switches} in series.:wi:t.h. the resistive elepeiit contri^iites to the me,as,iired resistance, creating, a Source of dtrϋϊ. If : the ' resistance ' of interest is ήόt.nni<ili-.lai*g(3i v than sueh.additional parasit-ic- resistanGe/then an. aliexnative moihαάis erαplόyed which. relies όn.twό iadditioxial terminals ' wHclip^rforxh a

9. K sensing Ixαnetion (often referred. to ais a:Kelmn niethød). Fig..iAillxisfcrates a-.p.ribr.εuft approach for- sensing: the resistor tatniinal voltage wh^ii: fbr-cmg a Voitagδ 4^qss--tli&,rfisisti' ! fte ' '. : 6li-iin6iit. Mg; IB ilinstrates aϊiotkeϊ prior art.appiOach for sensing the; rqgis$or. terminal voltage when fereim^f

current across; the resistive, .element,

|0004] ϊh;Fig:lA, the/.-S$pped; voltage difference Vi- ^induces a current in the fest-res.istor.1.0 . 1. (E)- which pi-oduces the -voltage difference.

V 1 ' . -\ζ, . Tϊi€i: ¥όltagis:4iffeϊeiice i8 sensed byfαrciήg-ai negligϊbte cniTeϋt 5 thrbtigli e&ch sense terminal lie.-, mφέ terminals .1 fiiid ø)- and measύrmg. a resulting voltage øii t ' he sense ' terminals. Tte current> % βowang tlirougii .eitl#£ teϊmmal.l or iettmϊ%θl;2 is ineasύred,;and the test

I'esistaiice. dMei'iaitied. as E ^A ';1 ~ -PM .. Si2ice;ffegIϊgiBle .ciύτeiϊtis passing tlirgugh, parasitic ϊ? : e?sistance^.rήet)έ«i . ,cmd TMot < ύά2 f tEfty clo not 10 contribute significant erirtiif fe a .determination qftne current I. Nor do

I'sewse! and r S pή^^.iϊitto|iqρe a ; ..sϊg£ώβc.aϊit vo.Jfege drop, allόwiag: V 1 ' and.. Vg to be; directly associated witii YpItag.es. measured: on their respeetive. sense terminals. In- additioiι >: .ad<|itiojial parasitic, resistances ' ∑i &μ$. rg do ιιό$ impact the accuracy of .tK©; measiirement since V-I and V^. are sδn§ed X5: dkaetly,

[όOOS] Mg, IB viiϊiαstxates. arsimilar cό : nn.giiϊatϊόii- difiering ifirom. jPig x IA- only in that c^uiTentifLdWlng tHroμgη a test resistor 1.51 (E): curreiit $&■ forced ϊiii'ectly :by a .cm'i'eiife soύircβ 151 (I F ϊjbia^ . In hϋi% ϋoii : lϊgui 4 atϊoϊLS ? the ms^^urieaieiit :appatiatuβ inust ϊhøέig.ui'ø. the Voit-agSs: V^ έtad. V^. iϊi. 20 ' bi-dei- to dό'terinϊne; the rdsi^taiice of.tlie ϊfesistbϊt 101.

[0006] In the/event that, ϊhe parasitic resistances: l'l aaid Ti axe very large compared with .tλbte test redist ' or lOij .accuracy liiaitatiόriδ adse.. For a given force cnri'e.nt (lbms% or applied voltage Vi. -%, the voltage drop across the test r ϊeisistθr:lθl scaies with a prdpprtiόn4^ity ^fø ,. , . λ \. ϊf

2δ the -vci . ltage drop across theCtest resistor ' , ipi become sufficiently small, noise-rindnced voltage flnctoations iathe meastiremaiit system. can.. caia.se accuracy d ^ egradatioii : and/or long. r.e,q^ia:ed test times.- Test.

<® ,

insfcumentation cariimmimize Random ftααse error bttt at the eiφ.&nse-.al μsing time, averaging, techniques., thereby in.cr.easi»g test time, (often cόn:sidef;al;.bly) ; Resistance :iiionitόϊitig ,&p|>Hea.tiiόiisiii. ; : a pϊoduetϊόa ma&yf&ct.uiing . environment may not, be ρMe: : tα accommodate, a resulting. 5 ■■ re . dμcfcioή;i.i .tbiOtiglipttt.

[00.0.7] H.S,.Pat.eot NGS, ββl$M% tg (Mm : a.a# 6,.3.6:2 V 63S Aslitøn, et al, βaόii dφscϊibe ■^nVag ' pIieatH.pϊi. fot.ni^stsύting tlife iϊijerfacial resi≤taήcesφf iαtøgrøte.ά ciϊ'CT-ϊii films .which are, rep.areseiatatixre of.t ' lϊe pxøblein described- abo.VG>. Hoive.vøri. the vsma.U!iB.tei-Cacial?esigt; ? L : nces,are measxired wsipg a 10 force/sense: itieώod .whiiSiϊ must iresόive small voltage drops. Loiig test tiisθv^ can result to. countei-act the :advexse.. effects. of system noise, when ^eH^UiirigsMali resistances.

[0Q,p$J ^heyefore^ whaiis iieeded. is; a;H f lectriqal xesistaace me a^iirβmerit apparatus aiid. method oapa^l^ of both accurately lδ measuring ' sjaiall yalsaes .of: resistance andiή. a- tiine-frarae eondticive to- IJi>pd : u.Gfcioa;ejo:ia3.O^m6n.ts.. The appaϊ'a.tus.a.B.d method shoxxld furtherhe capahle. of acfcuϊ&tely rαeasuriϋg'the ' sϋiall.tefeisfcaϊice value i&. the -presence of serie&-e,pime.cted parasitic resistanee y.alues that xpay be .Qi'fϊiers .of ,iilagnitu,d;e larger than the ϊesiέtor ϋiideϊ". te&t ; -:

20

SϋimαiiYOF .THE γNVENTIøISγ

[0.009J In an ..exemplary embodiment * therpxeseiit- invention Is.an ele:c ' ti > onic;.eii. v αμϊ^ to determi^ei a.re.sistanc.e yal^-e of . a. resistive element. The Gii'Ctϊit includes a cύϊreϊife sόtii'ciθ .ύOupϊedin series with the resistive. 25 elemeiit. The. current soiirce is ?Qniigiir.e.d jo force a. predetermined yalue pf curreήl tli EPiigh the resistive element: 'Xh&^iii'cuit further inteiii^es a ti"ansc.ondtictiiιg : . device coupled to- the' eurrer t fcsQ.Uϊce. The. tr : a.nή(2p3aductiii;g device is configured to sertse.- : a,yoltag:e across the resistive

eleϊήeiit and transform the: voltage ante aft output current; of ths, teanseαndu^t jng 4eγice svjcjh ifoa| th.e output ciirXentiaiipt dependent upon βϊLβ όtliier- tei'miiial voltages ofihe tτφxscϋϊiάπøimg. 'device-.

[00.10] Jn another exemplary ^^ ^iεLbG(^MeM > ' the present, itivexition is a.n 5, eiecttorrie circuit to determiϊie a ϊesistatice λrώiϊe ' of a :fbst reβϊsMva elem^ϊLt. The eircuib includes- a, .first eurrent-source. coupled, m fsexies: v f ith tlα4 : iirfet : tesiέtive eletti&άb aϊid. trpiifigti^ei t^ fc>ϊce a fir ' st pr^defcfeirmtined vaiiιa ; oi5 βttj * £en.t through ϊhβ. first ,xesisliτ\?.θ. eleaiextt. U second- resistive eleitie.β.tis.:cOupled..κi,sei^.s with. tfte : |h#. ■i"esistχy.e:.ele.pιø.ii4 tKtis fόnning ptό- & iϊødfe A second cijβfent source is cόύpled to t : he.#rst- : Gtm-ent source sueh. that the first resistive- element is coupled therefee&weeii:.. Tha seeαnd .Gμή'eϊ|t.;s;ouice,.:ts fύϊther eowpleά in. series witlt. th,& settoηd rβ$ϊsti ' vB eieiήent at the node and Is configured to ibfce a seeάϊϊd.pϊedeterniined •Yajuevof qtirrent into .th« : nød.e. A transcQnductmg.demce.iacpupleϊl bo.th to

15 tϋe : nr ' st ctirrent pburce and the; lii'.st and second resistive -elements.- The transcondueting device. is ccmϊigured tQ sense : .a.&st folt^ge- acroSvS έne :jSi F sta : nd second resistive, elements .ebupled in sefies witlx o.ne. : anpfciher and tfanslorήα ifaέ first .voltage in'toValϊ όtitptit ' ctirreirit :df tlie tfkήgcblϊdttctmg .device/such that the.piitp^t cm-xentrjs not..dep.eB;den.t.up.on.an3 ? other

20 -terϊiciiή.a.1 Voltages of the traiϊscoκduettøg..deviefc

[Oi)Il] In another e^emplaly e;iJibpd:iineiit, th& present iiiTOiition is an electronic circuit to determine a resisfcance ^altte of : a first . ' resistive element. The : .clectrQmc .eircuit: includes a. current sotirce. coupled to the resistive element. The-ciirrent source is coαirxgύred to farce a

25 predetermined value ofmrreixt tnrough the: .rβsistd?;©. element., A first trans-cόndiictiήg device; is coupled to the i-esist;ive:elfjiae . nt; arid is; cøn-r| ' gϊired to serise a-iiϊst ' voltage difference' between afest node of th& tesistiy.e elexαent and:a relerenee vόliagβ, Tlie first tr^ansconducting deyioeis fui'tliei' Configured tbi transforrn. ffierβ^I'volfagfS dipga^erice ittto ' a

3® first όtitipύt curiBϊrt όϊ the first transcϊiJiidttetog δevifee: sueii. that tlSllBi!

ouiput : ciiϊreήi xs-aot dependent on iύay other ferήiiϋal volta'geέr of tlife ti v aB:S.eoi3:dιi.cimg..deyi!efi;. A.second fcϊanscondHcting device is coupled tp-ij ] ie- re§£a^ye-elemθ.iit-:^n.^i λ s ' cόipL^i^feci; ' t<a sense ^Sfeeoryl yolMge dififerenc;^ between a second node of the resistive eϊeϊneήi:.and-tb-e reference, voltagev 5 The -second feraiiiscόii^ttcting de;yice i : g.&rilier coiifigured to transform the- Second volMge difference into, a .sβ.ccϋiid, oαitptit cm^eiit of. the ^ecoM. transcpnductiiig device snch thai the second output .current is not dependent on. &ixy dthex terminal.voltagesjof tKeføginsepnd-uctmg; .device..;,

[0012| Xn jtiiother exemplai^ .BiBfeodiment, the- present inveiitio.n is a 1.0 nietn,όd.fόr: deteϊ'ώiniήg a value of slectiieai re^istaήce-, THe ϊnethόd mcliides; foreing. two. or ϊnore values of known cm'rβnt tkro ugh a resistor

Under : : t.est : .t.G piO.dnGa;;t^:o or more, voltage s geaaer ate d across, the resistor.

Eacia όfthe two or More voltages generated actδss tile. resistor is added to aa.a-djiist^ble.: constant, voltage thereby producing two or more voltage. Io su33as\ Each of the voltage sums is separately i;applied to an input of a

: transconducting device and. a current from the. transconducting device is. . generated based .on each of the applied: voltage surna... The generated

Glϊrfent varies dxpqaentially With the?appHecl voltage 'sum. Bach of the. valtiøs of ciαrrønt generated by- the traήsøondύeiϊiig device is me-as-ured.-at- 20 Uyϋ t ό ' r mprέ" valu^ of the known regiβtpr ciirrent. The value of elee.trical : resistance is; calculated from the resistor taider -test frόϊή.eaeii of the .meas-ured.- values of current generated by ihe. traπsG.onclilict-mg- device at: "two or xnόre values of the ktύwix resistor cμiϊ&tttt

%6 BMEW βES.GBϊPTIQK OF THE DRAW1N0S .

[OOlBJ ^ig«.. ' lA..is an 'electrical resistance nteasmøϊne;at'.ciϊ'cu.it of the prior :-arfc wliiβh: : oρ.eχate|J: by forcing a voltage aόipilfa,r;|sistive eleineiϊt.

- β -

[OGM] Eig, IBis miotϊier electrical .resistance:- m:ea.surem:ent : :Cir6tiit : of the •piξiør. ai:t whfck operates b,jr forciijg a,c;u,rreiit across a resistive, efem.eati

[G&lδj Fig: : , ' 2 is an θocemplarl: eieetiic&lrssistance- .rάeasui'eϊnθiϊt circuit in aecprdaii.ee. with an Bitibodimeiit of the present invemtiop,.

.5 [00 : l6] Fig; : .:3.:is an exemplay^electrical resistance.: measurement; cjreuititi .a<3QαrfeLance.%itii atiotltei' embp^iBiejiϊt of th& :ρrfesent -mv^tidii,

[0]QX71 Fig, 4A is:.aii exemplary, electrical ϊesistaμce meas.m'em.eiit circuit; in. aceoKjiaiieB witϊϊ axiotlier erabpilim . 6 ^ ®£ ttø- pfθsent : iiivθijt|ø ; ii.-

[00183 :.Fig- 4B is a modified yersioή of tliβ ©xemplarj embodiiiierit of ' Eig, 0 ,4A,

[001.9] FigL 5 is . . . aft exemplaxy electrical. resistarιqe;..ftiea$uM aGco.rdan.ee with .another embodiffiøϊit of the. present invention,.

|0:020] M|. 6 Is anexemplaxy EoWchart iiicHpating pi. e£8x$$ki$)MQ$ip<i in aceerdaiice. withvan embodiment of έlie present inwisjiiioa;

:5.

-D]EmI-LEI) DBSCϋϊP.TϊON ''

[0:0213 ' With Xβf&ence. to Fig. 2 3 an eXfemplaiy electrical iesistanqe :meastit*eriaeήt-tesb ciϊcuii. includes. a. resistttf under test 201 having; a : : ϊeaϊs . tance value of.B, :a Erst parasitic eg^iValentresistor^OS having: a 0 resistance; value of 1% a aeeond parasitic feqxxivalejxt resistor 205. having a I'esistaiice vaiμe of rs, a firøt sensing trandsior !^Q7 (M 1 )^ and a,ftrs| current, sdurce 209 having a..st.atic;ciirrent. y I b -. Fig. 2 ' M mstructϊye for- esplkining fundamental operating principles cOBimoft to aE. βrαbϋdmients ^scribed lue^eii?.. The resistaiϊce valtte,- S!.: øf tlαe.resϊs.tor taiader test .201.is 5 ' to.B.e :me;ά.s.τirMv : TJiB fest :203 and second 20§.piar4:s . itie e^iϊivlilerit

: t*βS.isi:ora ac.CGtϊnt &>x valttes: of:ϊesis.t.aiace: .^sSOθiate:d.witlx eixcυdimratig,

coπiϊecfoϊa, and asiy switches present le'ading to * a measui-e ' ϋϊθnt instrumentation.: device. (not sliow^i)- 1» a;sp,eciEc! eχiB : nτ!:|3la.ty; βmbQdiiiien^ thθ%^.-sdrisiiig.traasistot : 2Pf is. a . PMQSFET dencB,

[.0.0^2] The -BXeIiIj)IaItT. electrical resistance meas.uϊβ.πifitfϊt; test eirciriϊ. of o Fig. ; 2 i ' s : |>articula:riy- adyantageous^ when . a?f . elsisfcance valtiø R of tijie resistor urideϊ te.st,20.i is mxicli smaller than, se.paa'atβ. oi ? coMbiiied i:esisfcaiic.β:yaKιe^ : όf thό : βrst .203- :aiid secGixd 205.β4i-aβi.tic equivalertt- resistors. Iu tins case^ .direct- measurement; ό£a voltage- 4^Op aciOsS tlie- resistor, tinder test -201 by a foiWseuse , method (as .described above) .can

ϊ0 beeαme iiiaccurate Itέd/oi time consuming diαέ to t!ae-,srαall size of the voltage attd its concomitatιt;susGeptibility to noise. The exemplary electric a.l:i;eg|^tan:fie measurement test circuit. transfoim^ tlie resistia.iiC'e.E. of tϊie ' resistor :tϊii : <i#r; test 201 . into a. current (I) at te^niiiialVa WMctiis IeSs susc.βp.bilale to the: acemraey and measurement. time Mmitatioas :θf jptfior art iδ approachesi-

[€|02βJ IirPi^ %. the εxβt sensing transistor 207 :ponyerts :a g:at©-to:- soϊii'cfe- voltage iϊito dr-^in current L Sirice ' t ' ϊia fij.^t cui-i ? βnϊ source 209 foϊGe s- a . kn(iwn current Ib thrdug-h .th.e. resistor uade-r test ' 2QIj. a magmtiαcfø ,όf gate-tQ-soύrGfe voltage- of tBβ.fi^st.sensiiig-tϊmnsis

%ύ. -ø£.% aud fi (iieglectirig-- any .le-a-k-agδ current ttoough : ' th& : §ate of tlie- ϋi > st ^n.sing:.traπsiβtø : ir5 : 07). ; ; The sqiirce and drain bias. αf-tfre- UrStVSeHSiIIg- tMiϊsϊstόr-Slό?, clet^ir^iiϊi:ied by terύiiiials Yi.an<i Yt resia.e^tivelS'', is set su&h tliat the drain current I -is modulated only lory the gate-to-sαurcia voltage. Th ' e. gate-to.-so ' vU'ce voltage. in turn depends only; (Oή.Iy.aήd.B. This iβ. iδ adconiplislied by; selecting the source voltage. V^and dta:iή voltage V%- of the transistor such that

V 1 - V 2 ^

and

w;kere,lc.i.S;.BDit2maim's constant (1.3809.9 X iø- 23 jpules/°lf)y T is teMperatxir© ( ώ E), q is^tlxgi electrpmc-ch^igβ ;(1:6Q21.8 -x JO' 19 eoμloHib), and. Vt Is tliβ tliresiiold. vδltage : of ike .first s©iisiiιg-tχ%ϊisistoϊ 207; This biasing 5. arrangement places the, first sensing;. transistor 207 into sufethresboltl cdMuctϊoil with a suffacleiitly large dx'aiivt : θ^ . Qip?.d : e roltago; sucHlKat the draϊή ttii¥e:iit I do.βs not dόpfeiϊd on the drain^tq-solttt.e voltage . . ( ψ^ - ^); Th.us, the- di'ain Qμrreαt is.ixisen.Bitiye to the parasitic resistance 1'2. OH: the άrέtiϊl. tδrMinaϊ (terhϊmal ¥3). !TIie .dram current 1.8 also inseπsitiye tQ : ihe; 0 χ>ar.asitic reδistaixcBϊi of the sondes terminal (terminal %ι) : giϊϊ.ee tli6. drain ' cui'pa.at does iiotiiiiEluenGe the :gate-to-source ; voltage.

[QQ&41 Wiih:c.oήtxnuea.;:refer.ønβe tσ^ig^ ^ la s^bthresliold øp:era;tibri : w ' ith.a ^ufficieήtl3^.1a>g#dr^ the draϊri ywrreiif of vthe ; first seiisiiig transistor ^Of i^ given, by:

I- R^ 4 W

•vyζhθrje. ^ . ~ψCφ #a^i K.ls-.a..bi.as-indej?eκ4eiit pi*e.factor ^vhich idepeiife : uppπ. the size, threshold voltage ): and. other param ter's of the first sensing ttatisislϋr -2Of -WBIpIi deteilHine ; the ^ttrrent drive of the firp.t S.ensiiig transistor ?207.

[002δ] Dife-reήttøt&ii the .dr ' aim current I with respectto cύltfeiit h yields;

B I «,] J

Thus; E.can.tos; ύl'tgirήii.nøid: by meaisUKirig the έlope of the natiiraJ. logarithm of draiϊϊ:.cu3?r©nt I-.plotted. as & :ruήctioϊx ; όf the Bias : ctiϊrent Ij,. (jand sqaled by •a.fac^dϊ . of ^ Tt ),- T>$B; tp the^Xpbheiitial l±atoi'e of 1

fonctio.n of Ib > tϊie Bias^nSep.endertt pϊefa&tor K insfeϊi :ϊi<3it fo.e. kiaϋtøn in order to extract the- value.iøf $&>

i&02 * 6i ϊhe 1 ability to -extract, the valύi?. of R-. independent of tfe. dϊain., qurjen.t-s>jcef^ctόr:Jζ is a sigmficstiit advantage, since; |Ke/.B.rop^rtiiBs pf tho first sensiiiig: tyaήslstox 207 » -or fhose. of . aaoth.es PMGSEiST similaϊ tάr^he BxBt sensing; tø'&iisistor 2B%.- ψonM.mdϊπ&vily, need to be measured in ©itdei 1 fco: determine tH@ Ϋξdn&StK. If the £t ; rsfc S6 ' &ping/featisϊ§.t^ϊ; 207 : itβ&lf .^.βri* to -be measured {Mreci%:io ' idetermme : ε, the n an©tiαeϊ ch-cmt esoϋfigiiratiαn w:Qϊild, ] ϊe needed sιiβlα.t|kat-.a 1 l∑;npwϊi YQltage. eo.uH be. applied dipeclly. to the

10- gate of the first sensing; transisϊor 207, $ueh a.ine^si^etiieKt.woiiidsu^i? inacenracy in tlie.gresenee øf.non?:negligible parasitiC:resi.6tanceg.(e\g:., π WLidm) ' , and degrade: tfee acjjul-acy of.the method.. If a.. : differejat PMOS^JST,. •similar to. tiie..fiϊs.t sensing ti'aiisi8tDr2G7 but cohnβGted tό thδ tβlst instrunientatioii witko^fe. §igmfieant. : p>arasitic series resistance, is used-to,

1.5 deteriaine. K, then. aii^ .migϊnateh. ia the drain cutreήt between this device and the. first sensiiϊg.transϊstpr: 207 would degi*ade : the accuracy of IC .and- . hence the accuracy, of the R-λϊalue extracted.

[0027] 1£ both :ike 2?Q&ist0.ia.ce. R and the -.current h are smβSX^ihen &e; gate-tq-source YQltagδ ;έtn.d,.the re^ultilig drain cιιrr#.nt : will also B^.lόWi 2.0 Fig. 3 pr.ovHes a mechanism far adjuStihg-ox tuning the magmtϋdeí.αf. .drain, cμiτeϊit I bήce -fehe; circuit is^iponstr.tic^ed,. thus j>rpyidmg for an v optimally accurate and eMcient: measureiaent-

[0028] In Fig * :-3-, anbtlie. ' r exeinplary embodiment includfes- the cimuiiόf Fig. ' 2-pltts a second ϊesiB.tots 301 having a resistance ' value of Es aaad-έt 2δ second purreαit ^usce $03 providing a static current of.ϊbs. The .second, resistor 30.1 and tlie ^ . eepixd current, source -SQS are used tαshiffr-tM.gate-- to«s\αuϊ.ce voltage oϊ.thβ first sø.nsmg teaiisis.tqr 207 %-a feed amoμϊit. The additional ebngtanf g . a;tθ«tc>-sόurce volta,g^^ 3 ^y : eis v tQ-^ipe'th>;.^ai&. cπr^entnvithόut^clmtigmg: the sensitivity of the drain ' earreaat ' to Ib, ^sCϊL-,..

-M -

A .constant voltage is created -across the seiecjiidiϊsiδistor 3QI by:fecirig: a eemstant : :cm>rent thxougkitof value. Ib^ The constant current; is- acdomplisk©d^s Xbi# Yariecl by fάfciϊig a-etirrent of vklue (ϊb s - 1 Ib) ' in tb.e seeαnd : eurr,ent source 3θ3 ;(as;lo3i : g ; a!S tlιe : resistance value, % ? øf &e, 5 second, pesisiqr Wl remains constant)-

[00129] In tiie:.eγeiit.tEat tlie,flxst.se.nsing transistar 207 ejihilsitSλOrj.-

■αchϊm&d,hτ&esoύi)mg%h.e first sensing transistόt 207 current a;s-

l : 0 where B. HθW possesses a- wealt dθpendeiζice oμ the.3iive ourrisnt I; . Irs. this; case>- the first sensing transistor 20.7 (or a,skailar deyicø) : must first be imeaswred iή : :a ^separate te§|.caafigur-ation to extract B -as a-function of L Then, when;! ia measured b^f the; present iiivfention, B(ϊ) i§ readily cal.cvilaled, g.ud analysis ..can proceed .as d^scidbed above iisiaig the value of

15 B(I) pre iously obtained* ^^^ < j pritainmg tlii derivative of B with respect tc j .l {ie. ?:: I ^ ygF|j) ' 4$® ixW^iW, ignored rα the exti-actiph of K.

.lcpm I in. fehis case. ' but to. a/^ood; apipi'OxiMataoil for PMOSFETs eicMbitiri^ n.ørmal .qxiiT.ent-voϊtagl eliaract^.ristdcs:.:

[OOBiQl With referenee tøϊEig. 4A ? - a tliύ'd ^arasiiic equivaient:registex ■20 401 Iia ; ving : a ' resistance value of ι% a ^ fϋui^h p^rasiiic øqmvale . h.t re$is;li ' (3r : 40S ' havirtg a resistancis value of ; £ϊ, and a second sensing transisto 403 (ϊVl2) are adiied^iid iisedWith anvadditionaϊ terminal Vi to enable adjti≤tinent of the gate4o-so.a.ixe " ybitage.όf the : fLi*st seiising ti^aήsistor : -207: In a spe.cilic •■ exeMplar•5•^øm b.ρdk-lent J tihe λ seGθϊid seiising transistor 4OE is 25 a PMOSFET. Tiie voltage, difference .. . (V 1 . ~λ?a). is siάάefi directly to tne

gate-tό-sourG.e ' .Ϋόltage of. the iii-si. sensing^traHsistόr ' 207;, thereby realizingi an ability fe tiine-.^rai∑i enxrent witli the. second senssing tranβdstoi- 40B- rj instead of with ' the βeftόnd j-esis ' tόr SOI; and,tb.e a-dditioual όuxϊeint έwέM

303 of the emboditaeftt G ' fMgi & όόήseclHen.t^.-άneilegs eurreni.soutfce. fimetiøn: is needed in ^a--^e.^^θm^ntαnstrijϊ)a-entaτ(;ϊθ-i utilizing the- eiribodiπaent of Frg. 4A: f

[0031] The resistance:. E is. e±β acted! in a m#maer similar to thai described ioϋ the exemplaiy embodiiiiβrit of E£g.- : 3, ahovie, Refέsrriϊϊg again- to Fig. 4A, the. drain curr.eiϊts of .b.Qtii ihe. fixst, ' .207 : and : the.:, second 403. έensiiig fcransistbrs ^aupe^iaeas^p^^X aiad .ϊa, respectively-., Thφ fwki 207 and tte second 40B sens : iiig iiiaiisisto. : rs are both biased iiito subthreshold όpei'atigh as with, the,em:bodiment s&t fbi't ' ii. withxefereneg to Fig. '■ $ . The. difference i ή .: : -gate-to^sourGe 1?bltag$ feetween the ' firs|. : 2.07.an:4 the second 4Q;B- sensing; transiatoi-s is (E.~.I b ). Thus, the ratio of dfaiii cύτrents.is :

JB-I^E]

witia a notation consistertt wiϊhjhe equation ^reβentedjhr. ihe :^mbodime.nt of Fig, B and whei^iKkls the dram current pr(?:factρr;Qf the, -Se.eond sensing teaiisistόr 403; The resistance- is exfeicted as

E,

' $. In rUir kin ^a

: α^: i • L4j K.

li ;

o lή J I

R - 1 - I 1 ^j

'L^b-

in a manner identical to that of .the enihodinient of -Fig. 3 using- 14

instead of L, ¥alτies of ;1E£ ap4 Ka-n^^ji notl)e: : identical; ;only their- ratio must- De.i ή dependeήt.of ' U* The-anaitsis teiαain ' s vaMd : as- long as t^ill-it.

.207 antibthe seco&&:408 sensi3ig:t : raήsϊst : ors,:exMbit idiϊg: channel, faiilfe device Behavipr: : $-αdh tiaat tii^r siib|hiTesih.ol<i;sI:opes.ai'e : similar 1 :.

|pθi2j ' Eif> 4B;.§iiow;ai ;an additlόnalfeatάϊϊfe-wliich-.m^y be employed to. furtjiβx adjiϊst -^ TheMdy of th^iirst 207 and the

5 seco iϊd ;4θ&-seridhg:: transistors rtfay fee. biased iii ' dislseπάbnt .of tlie comttrari transistoE source- to. adf-ust the: : thi'es-2old yoltage.-of e;ack.tEansistor..a.xid iϊisnte tiie : drain 'cϊφέx§nti This l?ia;smg όf£&t siari Additional, degree of control for oplima% iscaϋngrfcliβ drain : cmύ'ent h f applying a forward- ©r r$yerse $ody bias-.:

10. [0033] Eefemag now :to Fig,.0, aao&eϊ altei'natiye exemplary έϊiibb.diπiθnt uses, a^ipόlaf.tr^ϊisϊsfoϊ 5Q : 1 iβ§tea4,Of a MOSFET (e.g v , ih& ' iixst sensing- transistϋϊ 1 - 207. . Figí ≥). -In.^ Specific exerriplary embodiment,, tlie- bipolar, transistorβ ' Ql : ϊ$ a FNF transistor * ThB. bipolar transiBέor SOl is biased ϊϊitd fbfwsLrii active rnαde whei-e^the collector cml-ent; exhibits a;

1-5 isimilar eKpoiiefttiabl diBpendendeioit the basόj-toreiήtittervoltage.. If the

e^it ' tβr-tp-GDπfe^brΫpltag^ ^ ^^ ^ tϋiittjb. Xalcger tJbiaH ^§ζ >: tϊie;n the collector-

feHrrent depielids όli ' the base-emitter voltage as

■wh ! i3 ' re K; is a bMs-ϊ3adepiB)l^jBn ' tjp^fø^{ϊr; : UMike $i& JMOSFBT iπ BQ ::SBbthrgsiiόld.condτj.GtiQiiy thβϊe is via basaicm'i^nt iii tlie bipolar transistor, 501 ' -which., may .be comparable in rϊiagriitύde. tt). th^:c©He.ctor current (if the- forward gain όiiύϊe bipolar device 3,s-. earMiMt$>|).. ϊf-jiiasa- h» howev.er;. then the- bipolar transistor 80:1 in. fQ^yard ae ' tiyg,iϊi . o.de allows the -same extraLction :όf resista-rice E : as ώatB-^ploy^ ' ^Yil^^^ ' ^^^-^ i- 13 - : 25 siibthresliold .eoiϊductidn,: namely.:

1 .f 3|Wifj

Any. error incurred due- ' to Ibase .& ^ simply

B(aCϊiιal) ' t b

t ' ri : ffi&ny applications, Iκme wiay/ be Iwό-to three. orders ύ£ magnitude: smaller than TH.

tι.

[0034] Various. embqdϊmeή|s : of the oresent invention jiaay be ήέ&ά. ]?y appi^ing- BuitaMe voltages and currents iύ tlie circuit terminals and nieasuidng.tlie..resulting drain ;cwrreni : I. The resistance R is then

ID caic^ilatfeϊd by methods descmbe4 abwø > Giuxent SQiά'ce^ Bi&y be impleraeiited as connections diractl^ to external measurement: apj^r.aius, or to cuϊϊteήt mirror circuitry with svtiέable ' bi.4siϊig and control inptits. θne.όxemplary method of opei^ Mote that tiifcmeihod is exemplary only but a person of ordinary skill -ϊa the art

%β woήM teeqgnize ceλ'taiiα nlodifiog-tioiis tliat. would, still be; within a sGope of the: pϊαsent invention. Theϊiefόrβ, -iaϊnh όiliMeiits df ' tlϊe : ..in.ventiQn-. May -be jDperated.:in a manner differing from th^ following .seq . ueBee. > : ' b.ut ' preseϊMng conditions- fdr prθ|> : er opel'Sition ' as ds^erib^d ab'0.v(5; .

[Q035] Referring now to Fig. β -aiid rθfe3?riiig.hack to Fig. 3 ' , ajo... 20 exemplary, fiύ.wtihart 600 preseiits: : a method of ^ne ; as^^ϊ^ng electr&al resistance utilizing one. of the VaripWs circuit . qrabodimeints desciibed. liersih.- A skilled artisan, will. re4ogniae : . ψhicil values χά&y rieed siibstitiitiQn.based βϊi, for example,, the type of transistor selected itϊ the; meagiu 4 eiiierit circuit x [0.0 ' $6] Initially, a..user- will: ^eleet. β OJ the . magnitucie desixed. for- φ-ain Ciirreii:t:.I.ba|e(i QU . accuracy eoήsideratibM

hardware. ,A v&iάe..of gatevtα-source voltage iέ estimat&d, 603.that is, needed to, achieye, ' tlxe Seskecl .magnitude ώll bas$$ .oil an approximate ikrio.wlfedge of teansistdr- ' Ml properties. A. maximμm.ystlue ϊor bias, ctm-eiit. Ibis set. 60S based on (a:) a desired gate-td-sόarce voltage (Vgs) όibtarάed 5 from. th,e preceding step 60S 1 and (b) aii<aρprακimate.:'yalue of the, resistor

R aiidrfcke relatioϊϊ .^(ftiax^ " ?| % ,

[0037] -A value of the .mimmύm forcfe-cxirreήt? pj»in| ia selected 607 sucji. that the valpe isvgreater than- the leakage curreϊϊi flooir of the : measiii-emeiit apiiaratus and tββt enviiOiiineht. The/cuiTeiit lb s is . set 609 10 such th.at:.ϊ p = ϊ^ iti -fϊ^^ϊiax) . A value for starting curreiit ώ selected 611

.sucktEat. I^ > ϊ mih . , YόMgeS:før. -V* and Y& are forced .;6.1.? sμch,tha.t Yi.=

Vd<i andλ^. ~ 0, whem YM is:t&e maximum φUppiy) voltage,- Current valu0s;.ar^,.lbrce.d 615 seqαxe.ntially; Ib then Ijb. s - l$,χm the ilrst 209 and secoad 30$ curi^nMDm^s ^ respectively ' (Fig, : 3},. ; Current. is then .IS: nafias.arftcV 61? on teranirtal -Vk

[003^] : Tile: v,&kιe.ό£ Ibis- then i∑i.Gremeήted 61©., A.;&terϊϊiiτ3:a.tion β21 is m&4$ whether :\ > I fe (m^|. If I^ ^.^{iiiax),. step:s: ; 813 — 61:9.are.i"epøai;ted λϊiitil I h ' ≥ %(Max}. iEiiiaii^, the resisttee^ value R m&y be extracted 4ire:αtly in, accordance witfh the: gQvexmng e^ations discussed abov:e. where m H.iø- thβ..Blφe : of ln l^ plotfea againstii, f E - y£g :&έ BJr)I ' .^

.røO.SB]. Steps .001. --.βl.l may lbe : -applie.d..d>mng-'the,:q^ i>ih,a.s:e

: so tliat the vahϊe of i-e&istbr Es is Selected. as

lt ώ ^ (H ^ rlbfea^S

^b 6

wiϊerø jE^is-όjϋ eistiirtate of ϊk& value c>f fesistiof iR.

A&ύiϊrviages ofJBmBσdinϊetϊtb of'thelμveτitiόihp,ver BriprAri

[00£0| : Nuiήsrous advantages are-^^^4. : ^Q;m ^ d : SS!^iptii0''ia'S: of 'the present iiivaiιtϊθtχ:s©t:fόrtϊϊ ^ Mfeiti ^ GQU|)iφ^ i^itE aϊϊy ϊϊi(ϊdifi.catipns : :tp. em]bθ(iϊmeξite .Qftfe.e invention recognisable ' By a skilMϊi -artisan. Amt)rig-; fclϊes.e 1 ' advkxitagøSj the embodiiridhtsii .of ' the; itivention-allows- -accurate. meas.uiNsjnient of- a s:maH : resistance iii series. witE^iφ|i'lai?'|ι;e-*-..uii&i ! iό)w^ι. pέtyasilϊc resistances. The. sxαall resistance is-acCteratelv rjjgasured foff- s&ti&htφmi electrical- cntieϊϊt oil a terinitial whose ^plfcage,dpe.s; not need ;ϋo. Be known. Tk& m^gmhidfe of the sensed citiυeiii is adiύstabfe to a range . suited fof op tiiaal^easui ^ emeiit a.Gαn?g.cy; A.^plla^e meaaureiaieiit ls not ne*3{3M as reguifed " b^ths;pi*io-r βi't, tlras eiimiϊiatJHig accwaG^ Ii|aitatib.fts .due tα voltage noise ψ}χexι m&SLsnsmg .smaϋ voltage ,diHei*&nces β liai^eteiistic of.smήll tesl; resistances:, JPiirther . , the accuracy .of the sense current is -UOh depβndemt on. the size of pai'asϊtic eries: : ϊe^istaώ6eS:.'πGr Ia tϋe acGtiracy - " of : tlie . se^ge. øuyrent dependewt. on. the .emTemt drive: strenfth øf donstittieni transistois of the: sen.se. circuit.. .Smcis: neither the . siaej.of parasiiie se.ries : ^esistanc^« nor the etαa-eftt drive strteilgth of coiistil'uβϋϊ.. tf;aftsiB|Dϊs afe ϊeqtiiϊed for moasiirement, (iliaj'actepizationvof Batøi^onneet wiring, aiitϊ sfeixs : e.:cireuit dό^ic&ή is Hot needed; GόiiseqύeMty, the a.e . curadjr ύϊ ^tr.;|#;ed i'βsiέtantje is ; dep.enςtent only oii.fehe consistency of -tJbe: exponential nattiτe.-όf:the ϊest circiiit trMϊsistpr . eμii'eiit u&dei appiOpriafe bias G,oii4itip3i.s /:

[00431] Various- embodiments of the. iiaveiitiojl pr6γid.e a method and . dircϊiit appai-atus for accurately extracting the yalue of a small test resistance iii : the ρresence : of large, unknqwii .parasitic r.esis " tances in series witli tjh.e tesi; resista-aee. Suck a scenario, is ^commonly encountered in cIiaTa'ct^riKiiig lhte^perfόrm^ of integrated circuit; elements,, wkere;: iiit ' ercόnneer rfesislaiice aiώ switcϊi resistances ' can be rela ' tϋ^ly very large, TtiefiriΫeήtϊόn .tktis:.;a^oids,disadyaiitages of:.G.oinm<3i£ily used foree/sβase ^ β ϊx^;iiie^ό4^.:Sϊ*Glα -aø Voltagø noise SusceptMlitf ®nd ' sdftέa.lέaJl^pll

etesjeiit eirαi 1 .- The- iisvβntibcή. effectively traiisipirms the. tø : st resistance- into a Giirrertl;..wMiBh; can he sealed well above cii*gα-$ leakage levels ύϊxά ϊMό a i^aαge best suitθid.fθi 1 the imeaβuremeat matiimieiitafclon., As a res lt, fastei' .aiκ|.niore : . aecurafø me&stirenients of small re:sista ? ice afe possible i& 5 ' the /presence pf:parasitic resistances and measurement system lϊoiseL

Fabrϊcated as an fa£teø;$.t&ά circuit, embodiments :pf the inye . ntipn allow .muqk,greater density of xesϊstox test. structures than: traditional fbrce/øβn# tάst : :sti-Hetxιre.3. Area-^fficiertt . multiplexing techniques which ntroduce: series resistance and leakage c-urrent caii b.e utilized without 10 degi^atilng the accwacy of small resistance measuremettta ^

[ Q 042] ϊiϊ the foi'βgdiiig specifieaMon,. the present/ iήyeiitipia has heeή- Ufscrihed with ϊ'efeϊenQ^ It will, however, be ^ e y icient to a . skilled artisan, that various modifiGatiqήs ahd φanges can.be m&3,& thereto: witho t departing from the- brQaάer spirit m.nd scope, oϊ the:

15= present . mvøiit ; ϊoh. : a-s set .forth lit the. appended ekims. :For example, all eaiHbodimentg deseribed utilize 'p-typβ' .tr^ixsiltdi' ^lewents. Each .. ethbAdiotient can. be : xe&άϊly teansfornsed into , a ersioti: WMch itses 'n-.type' traήsisior elem^iatsiii a sti^igHtfofward manner 4p . psα?ejit : to- one sjαlled in. thei ixχ% of basic :,transistσr økciiit dδsigii. A scope of the- preseϊit iiiveβtion

20 ' co^eϊ-s siich: eases. whiβH ate^oiist^Ucted throυ.gh. simple, polarity i-eversal of voltages kϊid.ctif rents,- thereby, re tairiiag the same : ;claiffct§ a.S. thfe iήvqiitipn eϊτo ; |>.odii|ieiit.s .described in detail Further, -other lϊoή-ϊxήe.ar eoϋtrol devices besides those shown can.be ulsed to realize basic npn-line . ar pehaVioiiia tEe eircμiti;^, Additfenally.,- a skilled artii5£in.\v.m reco:gjjχ^e thatvai-iousi^pes of

2δ transistor tepMόlbgy. may be employed iQϊ the yax-icais emfeodiment^ desciihed, herein.. *Ehese other technoiύ^es.toclude .^ /for example, Bie>^QS } DMOS, .Qϊ: other trauscoiidtictiiig clevice eircmt-ry,. These- tech3o;ologies;»ia:y be implemented m ?: . for -φXamplfe,- silicon or QtMt el^møhfar s.ea-nicQnductQrs,. G)t-o.up. Jπ- : V ": orirr : Vϊ cθ33jtpo.ιiω,d s.øωicoήdχictor% : afid vaiious ailoy ' i? thereof- 5r

30. y.aridits sttibstratfe tf pes kxxβt as silicort-oii-insulator 02 1 . even ..n.oia-st

siϊbstrates-.suefaf asJa pόl^etiiι.^le3xetere|>lhtlialate (FET) feύbfl>i ; ate. deposited wiffi silicpn dioxide and polysilieoia. followed. tøy- an exβimBϊ.ias&r ansiealing $MJty aiiiieal step^ Each, of the^e ;feeMιdlpgy t $ ψβέ- and . jωtM^pais axe τecoψάz&bl®. to a sMlled artisanv : These ' aϊid.vsέxious: other embϋdlmetxts^ai-e all within aiiβdpe Qf the pr^sent inyentipiiv The specMcatiOiL ajid: drawings atfθj, acdo^dmgly^ to; foe. regatdedim aii illustrative rather thaii. α. restrictive sense..