2. 2.2 Rezistoare dependente

2.2.3 Rezistoarele dependente de fluxul luminos – Fotorezistoare

Fotorezistoarele (LDR – L ight DHSHQGHQW5HVLVWRUVVXQWUH]LVWRDUHDFURUUH]LVWHQ GHSLQGH GH IOX[XO OXPLQRV LQFLGHQW SH VXSUDID D HOHPHQWXOXL UH]LVWLY9DULD LDUH]LVWHQ HLHVWHFDX]DWGHHOLEHUDUHDGHHOHFWURQLSULQHIHFWXOIRWRHOHFWULFLQWHUQ ÌQ JHQHUDO OD UHDOL]DUHD IRWRUH]LVWRDUHORU VH XWLOL]HD] PDWHULDOHsemiconductoare cunoscute sub numele generic de materiale fotoconductoare.6WUXFWXUD GH IRWRUH]LVWRU HVWH DVWIHO UHDOL]DW vQFkW OD vQWXQHULF WRWDO V FRQ LQ

IRDUWH SX LQL HOHFWURQL OLEHUL SUH]HQWkQG DVWIHO R UH]LVWHQ ULGLFDW 2GDW FXDEVRUE LD IOX[XOXL OXPLQRV WRW PDL PXO L HOHFWURQL VXQW HOLEHUD L UH]LVWHQ DPDWHULDOXOXLVF]kQGFRUHVSXQ]WRU

Pentru structura din figura 2.180VHSRDWHFRQVLGHUDFQXPUXOGHHOHFWURQLHOLEHUD LSHVHFXQGvQPDWHULDOHVWH1 ηLld, unde ηHVWHRFRQVWDQWFHGHSLQGHGHOXQJLPHDGHXQGDUDGLD LHL/LQWHQVLWDWHDUDGLD LHLOXPLQRDVHOÂGVXSUDID DLQFLGHQW

l

d

U

(a) (b)

Fig. 2.180DVWUXFWXUIRWRFRQGXFWRDUHUHFWDQJXODUEIRUPDHOHFWUR]LORUXQXLIRWRUH]LVWRU

La aplicarea unei diferen HGHSRWHQ LDO8vQWUHHOHFWUR]LHOHFWURQLLYRUDYHDviteza v:

d

UEv µµ == (2.218)

cu µ - mobilitatea electronilor, E intensitatea câmpului electric./DFRQGXF LDFXUHQWXOXLYRUFRQWULEXLQXPDLHOHFWURQLLDIOD L ODGLVWDQ DYÂτ

de electrodul pozitiv, τ ILLQGGXUDWDPHGLH GH YLD D HOHFWURQLORU OLEHUL'HFL ODFXUHQWXO WRWDOYDFRQWULEXLQXPDL IUDF LXQHDYτ/d din totalul electronilor, curentulelectric fiind:

,d

UelL

d

veNI

τµητ == (2.219)

FXHVDUFLQDHOHFWURQXOXL'HDLFLUH]XOWUH]LVWHQ DPDWHULDOXOXL51

−== L

le

d

I

UR

µτη (2.220)

Cap.2 Rezistoare

2

'XUDWDGHYLD DHOHFWURQLORUOLberi τGHSLQGHGHOXQJLPHDGHXQGλúLGHLQWHQVLWDWHDOXPLQRDVGXSRUHOD LHGHWLSXO βλττ −= L)(0 , cu βRFRQVWDQWLDUτ0

DUHVHPQLILFD LDXQXLWLPSGHYLD GHUHIHULQ $VWIHOUHOD LDVHSRDWHSXQHVXEIRUPD

α−= ALR (2.221)

cu βαµτη

-1 ,0

==le

dA (2.222)

6HREVHUYFSHQWUXDDYHDRYDULD LHFkWPDLPDUHDUH]LVWHQ HLvQWUHVWDUHDGHvQWXQHULFúLVWDUHDGHLOXPLQDUHHVWHQHFHVDUFDYDORDUHDFRQVWDQWHL$VILHFkWPDLPLF$FHVW OXFUX VH UHDOL]HD] SULQ DOHJHUHD GHPDWHULDOH FX YDORUL FkWPDLmari pentru η, µ úL τ0 úL SULQ DVLJXUDUHD XQXL UDSRUW OG FkWPDL PDUH XWLOL]kQGHOHFWUR]LGHIRUPLQWHUGLJLWDO

3ULQFLSDOLLSDUDPHWULLDLIRWRUH]LVWRDUHORUVXQWSUH]HQWD LvQFRQWLQXDUH1) 5H]LVWHQ DODvQWXQHULF5D±UHSUH]LQWYDORDUHDUH]LVWHQ HLODLOXPLQDUHQXO2) 5H]LVWHQ D OD LOXPLQDUH ± UHSUH]LQW YDORDUHD UH]LVWHQ HL OD R LOXPLQDUH

VSHFLILFDWGHH[HPSOXOX[$WXQFL FkQG VH YRUEHúWH GH LOXPLQDUH WUHEXLH GHILQLWH FDUDFWHULVWLFLOH VXUVHL GHOXPLQ2FDUDFWHULVWLFDVXUVHORUHVWH LOXPLQDUHDH[SULPDW vQ OX[$OWXQLWDWHXWLOL]DW SHQWUX LOXPLQDUH HVWH IF GH OD IRRW FDQGOH IF OX[ 'HDVHPHQHD HVWH IRDUWH LPSRUWDQW FDUDFWHULVWLFD VSHFWUDO D VXUVHL GH OXPLQ 6HXWLOL]HD] FD VWDQGDUG R VXUV FH UDGLD] DVHPQWRU XQXL XQ FRUS QHJUX FXtemperatura de culoare de 2850 K.3) Sensibilitatea la fluxul luminos±HVWHDSUHFLDWSULQPDLPXO LSDUDPHWUL

- 6HQVLELOLWDWHDLQWHJUDO6HVWHUDSRUWXOGLQWUHIRWRFXUHQWGLIHUHQ DGLQWUHcurentul prin fotorezistor la iluminarea Φ, IΦúLFXUHQWXOODvQWXQHULF,D)

úLIOX[XOOXPLQRVLQFLGHQWφ

DIIS

−= Φ .

- 6HQVLELOLWDWHD VSHFWUDO ± HVWH UDSRUWXO GLQWUH IRWRFXUHQW úL IOX[XO

monocromatic (φλ) incident: λ

λ φφ λ DII

S−

= .

- Sensibilitatea fotorezistorului φφ

φφ

⋅−

=⋅

∆=

D

D

DR R

RR

R

RS .

- &DUDFWHULVWLFD VSHFWUDO D VHQVLELOLW LL ± UHSUH]LQW YDULD LD VHQVLELOLW LLspectrale SλFXOXQJLPHDGHXQGλ.

- &DUDFWHULVWLFDUH]LVWHQ ±LOXPLQDUH4) 3XWHUHD QRPLQDO 3N ± GHILQLW VLPLODU FD OD UH]LVWRDUH IL[H H[LVWkQG úL OD

IRWRUH]LVWRDUHGLDJUDPDGHVFGHUHDGLVLSD LHL5) Constanta de timp τGHILQLWVLPLODUFDODWHUPLVWRDUHFXGLIHUHQ DDSOLFULL

unui flux luminos în locul celui termic. Intervalul de timp egal cu constanta deWLPS VH RELúQXLHúWH V PDL ILH QXPLW WLPS GH UVSXQV FDUH SRDWH IL WLPS GH

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

3

FUHúWHUH ULVH WLPH VDX WLPS GH FGHUH IDOO WLPH &X SUHFL]DUHD FGHQXPLUHDSRDWHGXFHODXQHOHFRQIX]LLGLQPRWLYHFH LQGHILUHVFXOH[SULPULLvom utiliza aceste denumiri.

7LPSXO GH FUHúWHUH HVWH GHILQLW FD WLPSXO QHFHVDU FRQGXFWDQ HLIRWRUH]LVWRUXOXL SHQWUX D FUHúWH OD H GLQ YDORDUHD ILQDO FHHD FHFRUHVSXQGHXQHLWUDQ]L LLGHODvQWXQHULFODOXPLQ

7LPSXOGHFGHUHHVWHGHILQLWFDWLPSXOvQFDUHFRQGXFWDQ DIRWRUH]LVWRUXOXLVFDGHODH GLQYDORDUHDDYXWODRDQXPLWLOXPLQDUH

7LPSXO GH UVSXQV GHSLQGH GH QLYHOXO GH LOXPLQDUH GH PHPRULD VDXLVWRULDPDWHULDOXOXLúLGHWHPSHUDWXUDDPELDQWÌQJHQHUDOYLWH]DGHUVSXQVHVWHPDL PDUH FkQG VH OXFUHD] OD QLYHOH PDL PDUL GH LOXPLQDUH )HQRPHQXO GHKLVWHUH]LVPHPRULHSUH]HQWDWGHIRWRUH]LVWRDUHHVWHDVHPQWRUFXUHPDQHQ DSHUHWLQD RFKLXOXL OD WUHFHUHD EUXVF vQWUH QLYHOH GH LOXPLQDUH GLIHULWH 2 VWRFDUH DGLVSR]LWLYHORUvQvQWXQHULFYDGXFHODRYLWH]PDLPLFGHFkWvQFD]XOGHSR]LWULLODOXPLQ &X FkW VWRFDUHD H PDL vQGHOXQJDW FX DWkW HIHFWXO H PDL SURQXQ DW /DWHPSHUDWXULFRERUkWHYLWH]DGHUVSXQVHVWHPDLPLF

ÌQJHQHUDOWLPSXOGHFUHúWHUHHVWHGLIHULWGHWLPSXOGHFGHUHvQIXQF LHGHPDWHULDOXO úL WHKQRORJLD IRWRUH]LVWRDUHORU GH QLYHOXO GH LOXPLQDUH úL GH DO LSDUDPHWULDPLQWL LDQWHULRU6) Domeniul temperaturilor de lucru (T m, TM) 7HPSHUDWXUDPD[LP QX DUH

YDORULIRDUWHPDULODIRWRUH]LVWRDUHvQVSHFLDOGDWRULWJHQHUULLGHHOHFWURQLSHFDOHWHUPLF

La realizarea fotorezistoarelor au fost utilizate materialele: Seleniu cristalin-6H VXOIXU GHSOXPE 3E6 VXOIXU GH FDGPLX&G6 VHOHQLXU GH FDGPLX&G6HSeleniul cristalin are un domeniu spectral larg de utilizare dar are sensibilitateUHODWLY PLF 6XOIXUD GH SOXPE DUH PD[LPXO VHQVLELOLW LL VSHFWUDOH vQ GRPHQLXOLQIUDURúXúLSUH]LQWRLQHU LHPLF

Pentru domeniul vizibil, fotorezistoaUHOH SH ED] GH &G6 VXQW FHOH PDLXWLOL]DWH GDWRULW VHQVLELOLW LL LQWHJUDOH PDUL D FDUDFWHULVWLFLL 5φ H[SRQHQ LDOHOLQLDU OD VFDU ORJDULWPLF úL D FDUDFWHULVWLFLL VSHFWUDOH DVHPQWRDUH RFKLXOXLomenesc.

&DUDFWHULVWLFD VSHFWUDO D IRWRUH]LVWRDUHlor produse de EG&G Vactec esteSUH]HQWDW vQILJXUDLDUvQILJXUDHVWHSUH]HQWDWJUDILFXOUH]LVWHQ HL vQIXQF LHGHLOXPLQDUHSHQWUXDFHOHDúLFRPSRQHQWH

Cap.2 Rezistoare

4

Fig. 2.181&DUDFWHULVWLFDVSHFWUDOWLSLFDIRWRUH]LVWRDUHORUSHED]GH&G6>@

Fig. 2.182&DUDFWHULVWLFLOH5H]LVWHQ ,OXPLQDUHDOHIRWRUH]LVWRDUHORU(**9DFWHF>@

&k LYDGLQWUHSDUDPHWULLXQRUIRWRUH]LVWRDUHVXQWVLQWHWL]D LvQWDEHOXO 2.24.

Tabelul 2.243DUDPHWULLXQRUIRWRUH]LVWRDUHSHED]GH&G6

Parametru/ Tipfotorezistor

2322-600-93002Philips

2322-600-95001Philips

NSL19-M51RS Compo-

nents

NORP12RS Compo-

nents

VT43N2EG & GVactec

VT935GEG & GVactec

5H]LVWHQ D ODîntuneric RD

>1MΩ >10MΩ >20MΩ >1MΩ >300KΩ >1 MΩ

5H]LVWHQ D OD LOXminare 1000 lux

<110Ω 75-300Ω 5 kΩ(la 100 lux)

400Ω 8÷24 kΩ(la 10 lux)

10÷50 kΩ(la 10 lux)

3XWHUH QRPLQDO 340

(W)0,1 0,2 0.05 0,25 0,4 0,08

Domeniul temperatu-rilor de lucru

-30…+60°C -20÷60°C -25…75°C -60- -75°C -40- 75°C -40- 75°C

7LPSXO GH WUDQ]L LHFUHúWHUHFGHUH

10ms/200kΩ/s*

10ms/200kΩ/s*

45/55 ms 18/120 ms 90/18 ms 35/5 ms

* - parametru echivalent – rata de revenire

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

5

Din punct de vedere constructiv, fotorezistoarele sunt realizate prinGHSXQHUHD XQXL VWUDW VXE LUH IRWRFRQGXFWLY SH XQ PDWHULDO FHUDPLF &RQWDFWHOHPHWDOLFHVXQWGHSXVHSULQHYDSRUDUHvQYLGSHVXSUDID DPDWHULDOXOXLIRWRFRQGXFWRULDU WHUPLQDOHOHVXQWFRQHFWDWH ODDFHVWHVXSUDIH HPHWDOLFHFD vQ ILJXUD D0DWHULDOHOH IRWRFRQGXFWRDUH GHSXVH VXE IRUP GH VWUDWXUL VXE LUL DX R UH]LVWHQ VSHFLILF PDUH 3HQWUX DVLJXUDUHD XQHL UH]LVWHQ H UHGXVH OD QLYHOH GH LOXPLQDUHPRGHUDWH VSD LXO GLQWUH FRQWDFWH HVWH UHDOL]DW vQJXVW LDU HOHFWUR]LL DX IRUP

LQWHUGLJLWDO

(a) (b)Fig. 2.1836WUXFWXUDFRQVWUXFWLYDIRWRUH]LVWRDUHORUDGHWDOLXE>@

6H REVHUY GLQ ILJXUD2.183 E F UH]LVWHQ D IRWRUH]LVWRUXOXL OD QLYHOXO GH

iluminare L este l

dR SLL ρ= , cu ρSLUH]LVWHQ DVSHFLILFODLOXPLQDUHD/LDUGOHVWH

UDSRUWXOGHDVSHFW$úDFXPDIRVWSUH]HQWDWDQWHULRUDFHVWUDSRUWHVWHGHGRULWVILHFkWPDLPLF8]XDOVHSRWRE LQHSHQWUXGOYDORULvQWUHúL

([LVW úL YDULDQWHGH IRWRUH]LVWRDUHSHED] GH&G6 YH]L ILJXUD EUHDOL]DWH VXE IRUP GH GLVFXUL SULQ WHKQRORJLD FHUDPLF (OHFWUR]LL VH GHSXQ ODaceste variante de fotorezistoare tot prin evaporare în vid.

ÌQ ILJXUD VXQW SUH]HQWDWH GRX WLSXUL GH IRWRUH]LVWRDUH FX GHWDOLL GHrealizare a structurilor.

)D GHDOWHGLVSR]LWLYHRSWRHOHFWURQLFHVHPLFRQGXFWRDUHFXIXQF LLVLPLODUHcum ar fi fotodiodele sau fototranzistoarele, fotorezistoarele au câteva avantaje:• au cel mai redus cost;• DFRSHUXQGRPHQLXODUJDOLQWHQVLW LORUOXPLQRDVHSRUQLQGGHODQLYHOHIRDUWH

UHGXVH GH LOXPLQDUH OXPLQD OXQLL SkQ OD QLYHOH IRDUWH ULGLFDWH H[SXQHUHGLUHFWODVRDUH

Cap.2 Rezistoare

6

• DXRGLQDPLFGHYDULD LHGHFkWHYDRUGLQHGHPULPHvQWUHVWDUHDGHvQWXQHULFúLGHLOXPLQDUHH[LVWPXOWHYDORULGLVSRQLELOHDOHUH]LVWHQ HL

• SRWOXFUDúLvQFXUHQWDOWHUQDWLY• SRW IL XWLOL]DWH FX DSURDSH WRDWH VXUVHOH GH OXPLQ vQ GRPHQLXO YL]LELO úL

LQIUDURúX DSURSLDW /(' OPSL FX LQFDQGHVFHQ QHRQ úL IOXRUHVFHQWH ODVHUIODFUOXPLQVRODU

Fig. 2.184'RXYDULDQWHGHIRWRUH]LVWRDUH>@

$SOLFD LLOH IRWRUH]LVWRDUHORU VH vPSDUW vQ GRX FDWHJRULL ([LVW DSOLFD LLQXPLWH³GLJLWDOH´ODFDUHHVWHLPSRUWDQWQXPDLYDULD LDUH]LVWHQ HLvQWUHGRXVWULGHLOXPLQDUH$SOLFD LLOHGHWLS³DQDORJLF´XWLOL]HD]YDULD LDFRQWLQXDUH]LVWHQ HLcu iluminarea.

'LQ SULPD FDWHJRULH GH DSOLFD LL DPLQWLP FRQWUROXO LOXPLQDWXOXL QRFWXUQGHWHFWRDUHGHIXPFLWLWRDUHGHFDUWHOHVHQ]RULGHSUH]HQ úLGHSR]L LH LQVWDOD LLGHDODUPúLVHFXULWDWHHWF

ÌQ D GRXD FDWHJRULHGH DSOLFD LL vQWkOQLP FRQWUROXO H[SXQHULL OD FDPHUH GHILOPDUH úL YLGHR FLUFXLWH GH UHJODUH ³DXWRIRFXV´ FRQWUROXO LOXPLQULL FRQWUROXOWRQHUXOXLODPDúLQLGHIRWRFRSLDWFRQWUROXOVXUVHORUGHOXPLQPRGXODWHHWF

În figura 2.185 D HVWH SUH]HQWDW R DSOLFD LH WLSLF GH WLS ³GLJLWDO´ FXIRWRUH]LVWRUXO1253 úL DQXPHR FRPDQG RSWLF GH DF LRQDUH DXQXL UHOHX ODGHSúLUHDXQXLSUDJGHLOXPLQDUHSUHVWDELOLW3UDJXOGHFRPXWDUHVHSRDWHUHJODFXrezistorul semireglabil de 5kΩ.

ÌQ ILJXUD E HVWH SUH]HQWDW R DSOLFD LH GH WLS ³DQDORJLF´ XQH[SRQRPHWUX IRWRJUDILF )XQF LRQDUHD HVWH IRDUWH VLPSO FXUHQWXO SULQ FLUFXLWRIHULQG LQIRUPD LD GHVSUH VWDUHD GH LOXPLQDUH ([SRQRPHWUXO DUH GRX VFDOH GHsensibilitate comutabile, care se pot etalona din rezistoarele semireglabile R1úL52.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

7

(a)

(b)

Fig. 2.185$SOLFD LLDOHIRWRUH]LVWRDUHORUDFRPDQGRSWLFEH[SRQRPHWUXIRWRJUDILF>@

2.2.4 Rezistoare dependente de câmpul magnetic - Magnetorezistoare

8QPDJQHWRUH]LVWRUHVWHXQUH]LVWRUDFUXLUH]LVWHQ VHPRGLILFvQSUH]HQ Dcâmpului magnetic.

Efectul magnetorezistiv FRQVW vQ PRGLILFDUHD UH]LVWHQ HL PDWHULDOXOXL vQSUH]HQ D FkPSXOXL PDJQHWLF GDWRULW FXUEULL WUDLHFWRULLORU HOHFWURQLORU GHFRQGXF LH

2EVHUYD LH Efectul magnetorezistiv este diferit de efectul Hall, efect produs tot înSUH]HQ DFkPSXOXLPDJQHWLF

0DJQHWRUH]LVWLYLWDWHD GHILQLW SULQ YDULD LD UHODWLY D UH]LVWLYLW LL( ) ( )

( )0

0

0 ρρρ

ρρ −=∆ H

HVWH vQ JHQHUDO SR]LWLY 9DULD LD FRQFUHW D UH]LVWLYLW LL

Cap.2 Rezistoare

8

depinde de material, de unghiul dintre câmpul magnetic aplicat H&

úL FkPSXOelectric E

&

.3HQWUX FkPSXULPDJQHWLFH VODEHPDJQHWRUH]LVWLYLWDWHD WUDQVYHUVDO ( )EH

&&

⊥

GHSLQGHSWUDWLFGH+ 2

0H≈

∆ρ

ρ

ÌQPDMRULWDWHDFD]XULORUH[LVWRYDORDUHGHVDWXUD LHDPDJQHWRUH]LVWLYLW LLE[LVW PDJQHWRUH]LVWRDUH UHDOL]DWH SH ED] GH PDWHULDOH VHPLFRQGXFWRDUH

(InSb), dar cel mai des sunt utilizate magnetorezisoarele bazate pe metaleferomagnetice anizotrope, componentele fiind cunoscute sub numele MR.

'HúLHIHFWXOPDJQHWRUH]LVWLYHVWHFXQRVFXWGHIRDUWHPXO LDQLDELDvQXOWLPLL DQL DX DSUXW DSOLFD LL SUDFWLFH SHUPLVH GH GH]YROWDUHD WHKQRORJLLORUPLFURHOHFWURQLFH&XWRDWHFHIHFWXOPDJQHWRUH]LVWLYHVWHSUH]HQWvQDSURDSHWRDWHPHWDOHOHDSOLFD LLDXJVLWVWUXFWXULOHED]DWHSHSHUPDOOR\DOLDM1L)HVDXSHDOWHPDWHULDOH IHURPDJQHWLFH /D DFHVWH PDWHULDOH H[LVW úL R SXWHUQLF DQL]RWURSLHVWUXFWXUDO FDUH LQIOXHQ HD] GHSHQGHQ D FRQFUHW D UH]LVWLYLW LL GH FkPSXOmagnetic.

ÌQXOWLPLLDQLDXDSUXWPDJQHWRUH]LVWRDUHED]DWHSHHIHFWXOPDJQHWRUH]LVWLYgigant (GMR) efect observat în structuri feromagnetice multistrat de tip special.(IHFWXO*05SRDWHSURYRFDRYDULD LHGHDUH]LVWHQ HLVXEDF LXQHDFkPSXOXLmagnetic.

5H]LVWHQ DPDJQHWRUH]LVWRDUHORUFODVLFHFkWúLDFHORU*05GHSLQGHSWUDWLFGHFkPSXODSOLFDWvQFRQVHFLQ QXSRWGHWHFWDSRODULWDWHDFkPSXOXLPDJQHWLF3HOkQJ GH]DYDQWDMXO QHOLQLDULW LL PDJQHWRUH]LVWRDUHOH DX XQ FRHILFLHQW GHWHPSHUDWXUDSUHFLDELO

'LQ DFHVW PRWLY PDJQHWRUH]LVWRDUHOH QX VH SURGXF VXE IRUP GHcomponente discrete comercializate individual ci sunt înglobate mai multeUH]LVWRDUHvQVWUXFWXULGHWLSVHQ]RU$VWIHOVHPLQLPL]HD]YDULD LDFXWHPSHUDWXUDDPULPLLGHLHúLUHúLVHvPEXQW HúWHOLQLDULWDWHDVHPQDOXOXL

2vPEXQW LUHDOLQLDULW LLVHDVLJXUúLSULQDSOLFDUHDXQXLFkPSPDJQHWLFde polarizare, câmp generat de obicei de un magnet permanent.

(IHFWXOPDJQHWRUH]LVWLYvQPHWDOHIHURPDJQHWLFHDIRVWREVHUYDWSULPDGDWGH:LOLDP7KRPVRQ/RUG.HOYLQvQDQXO$SOLFD LLOHDXDSUXWvQVDQLmai târziu atunci când tehnologiile microelectronice au permis utilizarea înSUDFWLFDVWUXFWXULORUPDJQHWRUH]LVWLYH

&RQVLGHUP XQ UH]LVWRU SHOLFXODU GLQ SHUPDOOR\ DOLDM 1L)H (IHFWXOPDJQHWRUH]LVWLYGHDQL]RWURSLH$05FRQVWvQH[LVWHQ DXQHLGLIHUHQ H∆Rmax întreYDORULOH UH]LVWHQ HL PVXUDWH SHQWUX R GLUHF LH D PDJQHWL]D LHL vQ VWUDW SDUDOHOUHVSHFWLYSHUSHQGLFXODUSHGLUHF LDGHFXUJHUHDFXUHQWXOXL ⊥−=∆ RRR ||max .

La aplicarea unui câmp magnetic extern H&

, în planul rezistorului vectorulPDJQHWL]D LH M

&

VHYDRULHQWDGXSGLUHF LDFkPSXOXLDSOLFDW IRUPkQGXQJKLXOθFXGLUHF LDGHFXUJHUHDFXUHQWXOXLJ

&

.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

9

αM

J

H câmp aplicat

Fig. 2.186(IHFWXOPDJQHWRUH]LVWLYGHDQL]RWURSLH$05VWUXFWXUWLS05

6H SRDWH DUWD F UH]LVWHQ D PDJQHWRUH]LVWRUXOXL HVWH R IXQF LH GH FRV2θ,unghiul θ ILLQG GHSHQGHQW GH PULPHD FkPSXOXL DSOLFDW $VWIHO OD DFHVW WLS GHmagnetorezistor, cunoscut sub numele generic de MR, rotirea vectoruluiPDJQHWL]D LHVSUHYHFWRUXOGHQVLWDWHGHFXUHQWGXFHODFUHúWHUHDUH]LVWHQ HLURWLUHDvQ VHQV FRQWUDU GXFkQG OD VFGHUHD UH]LVWHQ HL 3H DFHDVW REVHUYD LH VH ED]HD]XWLOL]DUHDPDJQHWRUH]LVWRDUHORUODPVXUDUHDYDORULLFkPSXOXLPDJQHWLF'HRELFHLVHXWLOL]HD]XQDUDQMDPHQWVSD LDODOUH]LVWRDUHORUGHWLSSXQWHFDvQILJXUD2.187.

M

M

M

MJ

J

J

J

A

B D

C

HCâmpaplicat

+VA

R+∆R R-∆R

R-∆R R+∆R∆Vo=(∆R/R)*VA

∆Vo

A

B

C

D

Fig. 2.187$UDQMDUHDPDJQHWRUH]LVWRDUHORUvQVWUXFWXUWLSSXQWH

&HOH SDWUXPDJQHWRUH]LVWRDUH DX DFHHDúL UH]LVWHQ 5 GDU PDJQHWL]D LD ORUHVWH DOHDV DVWIHO vQFkW SHQWUX GRX UH]LVWRDUH DIODWH vQ EUD H RSXVH DOH SXQ LL VSURGXFPULUHDUHVSHFWLYPLFúRUDUHDUH]LVWHQ HL7HQVLXQHDGHLHúLUHDSXQ LLHVWHSURSRU LRQDOFXYDULD LDUHODWLYDUH]LVWHQ HL∆R/R, care în domeniul de liniaritateacceptat este ∆R/R=S⋅H, cu S sensibilitatea senzorului magnetorezistiv. Pentru

magnetorezistoarele firmei Honeywell, [40], S=3Oe

mV/V, iar domeniul de

liniaritate este de circa )/ 4/101(2Oe 3 mAOe π= .'DF FkPSXO PDJQHWLF DSOLFDW PDJQHWRUH]LVWRUXOXL GHS úHúWH YDORDUHD GH

VDWXUD LH DWXQFL YHFWRUXO M&

DUH SUDFWLF DFHHDúL GLUHF LH FX FkPSXO DSOLFDW H&

. În

Cap.2 Rezistoare

10

acest fel, θGHYLQHXQJKLXOGLQWUHGLUHF LDGHFXUJHUHDFXUHQWXOXLúLFkPSXODSOLFDW$VWIHOPDJQHWRUH]LVWRUXOSRDWH IL XWLOL]DW FD VHQ]RU DO GLUHF LHL FkPSXOXL DSOLFDWUH]LVWHQ D VD GHSLQ]kQG GH FRV2θ 'H RELFHL PDJQHWRUH]LVWRDUHOH FH OXFUHD] vQUHJLPGHVDWXUD LHVHXWLOL]HD]WRWvQFRQILJXUD LLWLSSXQWHFDvQILJXUD2.187.

Magnetorezistoarele bazate pe efectul GMR, pe scurt magnetorezistoare*05SHOkQJDYDQWDMXOXQHLYDULD LLPDLPDULDUH]LVWHQ HLFXFkPSXOPDJQHWLF(de 3-5 ori mai mare ca la MR), pot lucra la valori ale câmpului magnetice maiPDULGHFkWPDJQHWRUH]LVWRDUHOHFODVLFH050DJQHWRUH]LVWRDUHOH*05RSHUHD]GH UHJXO vQ UHJLXQHD GH VDWXUD LH úL VXQW XWLOL]DWH GHFL OD PVXUDUHD GLUHF LHLFkPSXOXLúLQXDLQWHQVLW LLVDOH9DULD LDUH]LVWHQ HLSRDWHILH[SULPDWSULQUHOD LD

( )θcos12 0

max

0−

∆=∆

R

R

R

R, cu Ro ± YDORDUHD PLQLP D UH]LVWHQ HL ∆Rmax valoarea

PD[LPDFUHúWHULLGHUH]LVWHQ ∆R=R-RoYDULD LD UH]LVWHQ HLθ- unghiuldintre câmpul aplicat H

&

úLPDJQHWL]D LDLQWHUQ oM&

.0RGXOGHYDULD LHDUH]LVWHQ HLSRDWHILXUPULWvQILJXUD

Fig. 2.1889DULD LDWLSLFDUH]LVWHQ HLODPDJQHWRUH]LVWRDUHWLS*05

$úD FXP VH REVHUY GLQ JUDILF PDJQHWRUH]LVWRDUHOH SUH]LQW XQ PLFhisterezis.

3DUDPHWULL PDJQHWRUH]LVWRDUHORU VXQW GH UHJXO H[SULPD L FD SDUDPHWULL DLstructurii complexe de senzor în care sunt înglobate.

Principalii parametrii ai unui magnetorezistor GMR de tip GMR S6 produsGH,QILQHRQ7HFKQRORJLHV6LHPHQVSRWILXUPUL LvQWDEHOXO

0DJQHWRUH]LVWRDUHOH 05 úL *05 VXQW UHDOL]DWH SULQ SURFHGHH FRPSOH[HVSHFLILFH WHKQRORJLHL VWUDWXULORU VXE LUL 6WUXFWXULOH FDUH SRW PHUJH GH ODPDJQHWRUH]LVWRDUHLQGLYLGXDOHODVWUXFWXULSXQWHFKLDUODGRXVDXWUHLFRQILJXUD LLSXQWH FRUHVSXQ]WRDUH FHORU WUHL D[H VXQW vQFDSVXODWH vQ FDSVXOH VSHFLILFH

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

11

circuitelor integrate SMD (SOIC, SOM) sau "through hole" (SIP, DIP). CapsulaSRDWHLQFOXGHúLDQXPLWHSU LDOHFLUFXLWXOXLHOHFWURQLFGHSUHOXFUDUHDVHPQDOXOXL

Tabelul 2.25 Parametrii magnetorezistoarelor GMR S6, [39].Parametru ValoareCurentul nominal de alimentare IN 4mA5H]LVWHQ DODθ=0, Ro >700ΩEfectul magnetorezistiv în gama H=5...15KA/m≅4%&RHILFLHQWXO GH WHPSHUDWXU DO UH]LVWHQ HL 5o

TCR0

+0.09...+0.12%/K

&RHILFLHQWXO GH WHPSHUDWXU DO HIHFWXOXLmagnetorezistiv TC∆R/R0

-0.27...-0.23%/K

Histerezis la H=10KA/m <2 gradeCâmp magnetic maxim 15KA/m7HPSHUDWXUDDPELDQWGHOXFUX7a -40...+150°C

În figura 2.189VXQWSUH]HQWDWHGRX WLSXULGHPDJQHWRUH]LVWRDUHDOH ILUPHLHoneywell.

Fig. 2.189 Capsule de magnetorezistoare MR ale firmei Honeywell, [40].

&LUFXLWXO+0&FRQ LQHRSXQWHGHPDJQHWRUH]LVWRDUH LDU+0&FRQ LQH GRX SXQ L GH PDJQHWRUH]LVWRDUH LGHQWLFH GDU FX GLUHF LLOH PDJQHWL]D LHLinterne rotite la 45°.

3ULQWUH DSOLFD LLOH FDUH XWLOL]HD] PDJQHWRUH]LVWRDUH DPLQWLP VHQ]RUL GHcurent, senzori de câmp magnetic, capete magnetice. Senzorii de câmp magneticSRWILXWLOL]D LúLFDGLVSR]LWLYHGHQDYLJD LHDYkQGRVHQVLELOLWDWHFDUHSRDWHGHWHFWDFkPSXOPDJQHWLF WHUHVWUX&DSHWHOHGHFLWLUHPDJQHWRUH]LVWLYHDXID GHFDSHWHOHGH FLWLUH FODVLFH LQGXFWLYH DYDQWDMXO F RIHU FD VHPQDO GH LHúLUH GLUHFW FkPSXOPDJQHWLF úL QX GHULYDWD VD $FHVW OXFUX SRDWH XúXUD FHULQ HOH SULYLQG DVLJXUDUHDXQHL DQXPLWH YLWH]H UHODWLYH FDS GH FLWLUH ± PHGLX PDJQHWLF 'HVLJXU H[LVWGH]DYDQWDMXOXWLOL]ULLFDSHWHORUPDJQHWRUH]LVWLYHQXPDL ODFLWLUHDLQIRUPD LHL$XIRVW UHDOL]DWH XQLW L GH GLVF ULJLGH KDUGGLVN FX FDSHWH FRPELQDWHmagnetorezistive - inductive.

În figura 2.190 D VH SUH]LQW XQ H[HPSOX GH XWLOL]DUH Dmagnetorezistoarelor la realizarea unui senzor de proximitate iar în figura 2.190EXQH[HPSOXGHXWLOL]DUHODUHDOL]DUHDXQXLVHQ]RUGHGHSODVDUHOLQLDU

Cap.2 Rezistoare

12

(a) (b)

Fig. 2.190 Utilizarea circuitelor cu magnetorezistoare în punte (a) senzor de proximitate, (b)VHQ]RUGHGHSODVDUHOLQLDU

În figura 2.191 este prezentat circuitul electronic complet al senzorului deSUR[LPLWDWHFLUFXLWFDUHFRPDQGDSULQGHUHDGLRGHLHPL WRDUHGHOXPLQ±/('

Fig. 2.191 Circuitul electronic al senzorului de proximitate realizat cu magnetorezistoare tip MR ale firmei Honeywell, [40].

2.2.5 Rezistoare dependente de tensiunile mecanice - Tensorezistoare

5H]LVWRDUHOHDFURUUH]LVWHQ GHSLQGHGHWHQVLXQLOHPHFDQLFHVXQWXWLOL]DWHvQJHQHUDOODPVXUDUHDUHVSHFWLYHORUWHQVLXQLHIRUWXULILLQGQXPLWHGXSIXQF LDSHFDUHRUHDOL]HD]WUDGXFWRDUHWHQVRPHWULFHUH]LVWLYHVDXSHVFXUWWHQVRPHWUH'HIDSW WHQVRPHWUHOH PVRDU GHIRUPD LLOH PHFDQLFH vQ JHQHUDO SURSRU LRQDOH FXeforturile mecanice.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

13

&RQVLGHUP XQ UH]LVWRU GUHSWXQJKLXODU GH OXQJLPH O úL VHF LXQH $ FD vQfigura 2.192.

A

Efort longitudinal Nl

Fig. 2.1925H]LVWRUGUHSWXQJKLXODUVXSXVGHIRUPULORUORQJLWXGLQDOH

5H]LVWHQ DDFHVWXLUH]LVWRU5HVWH

A

lR ρ= (2.223)

3ULQGLIHUHQ LHUHDUHOD LHLDQWHULRDUHVHRE LQH

ρρρd

A

ldA

A

ldl

AdR +−=

2 (2.224)

sau ρρd

A

dA

l

dl

R

dR +−= (2.225)

3ULPLL GRL WHUPHQL GLQ H[SULP YDULD LD UH]LVWHQ HL GDWRULWPRGLILFULLGLPHQVLXQLORUIL]LFHILLQGGHFLXQHIHFWJHRPHWULFLDUFHOGHDO WUHLOHDWHUPHQ H[SULP PRGLILFDUHD UH]LVWLYLW LL PDWHULDOXOXL VXE HIHFWXO GHIRUPULLmecanice, efectul fiind cunoscut sub numele de efect piezorezistiv.

5HOD LDVHSXQHVXEIRUPDWUHFkQGODYDULD LLILQLWH

ρρνεε d

R

dR +−= 2 (2.226)

cu ε=∆OO DOXQJLUHD UHODWLY LDU ν FRHILFLHQWXO GH FRQWUDF LH WUDQVYHUVDO VDXcoeficientul lui Poisson, ν≅0,3 pentru materiale izotrope.

6HGHILQHúWHFRHILFLHQWXOSLH]RUH]LVWLYORQJLWXGLQDOπ1 ca:

ερρρ

ρ

πE

d

A

N

d

==1 (2.227)

cu NIRU DORQJLWXGLQDODSOLFDWUH]LVWRUXOXLE modulul lui Young.6HQVLELOLWDWHDWHQVRPHWUXOXL6GHGHILQHúWHFD

Cap.2 Rezistoare

14

( )( ) R

Rl/lR/R

Sε∆=

∆∆= (2.228)

8WLOL]kQGúLIDFWRUXO6GHYLQH

E21S 1 ⋅π+ν+= (2.229)

ÌQSUH]HQWVHXWLOL]HD]GRXWLSXULSULQFLSDOHGHWUDGXFWRDUHWHQVRPHWULFH• WUDGXFWRDUH PHWDOLFH UHDOL]DWH GLQ DOLDMH PHWDOLFH FX UH]LVWLYLWDWH PDUH úL

FRHILFLHQWGHWHPSHUDWXUUHGXVVXEIRUPGHILUHIROLLVDXVWUDWXULVXE LUL• WUDGXFWRDUH SH ED] GH PDWHULDOH VHPLFRQGXFWRDUH UHDOL]DWH GLQ

VHPLFRQGXFWRDUHPRQR VDX SROLFULVWDOLQH VXE IRUP GH ILODPHQWH FKLSXUL VDXVWUDWXULVXE LUL

În cazul traductoarelor rezistive metalice efectul piezorezistiv este foartemic π1≈úLSUHGRPLQHIHFWXOJHRPHWULF

S=1+2ν (2.230)&RQVLGHUP F ν 6 'H IDSW 6 LD YDORUL vQWUH úL IDSW

H[SOLFDELOSULQGLIHUHQ HOHvQYDORDUHDFRHILFLHQWXOXL3RLVVRQúLSULQIDSWXOFSRDWHVDSDUúLRXúRDUYDULD LHGHUH]LVWLYLWDWHGDWRUDWGHIRUPULORUπ1).

2ULFXP6!LDUXQFRHILFLHQW6!vQVHDPQRFUHúWHUHGHUH]LVWHQ vQFD]XODOXQJLULLúLRVFGHUHDUH]LVWHQ HLvQFD]XOFRPSULPULL

În cazul traductoarelor tensometrice realizate din materiale semiconductoareefectul piezorezistiv este predominant.

S≅ π1⋅E (2.231)

S= 30÷ SHQWUX WUDGXFWRDUH GLQ PDWHULDOH SROLFULVWDOLQH úL 6 ÷200 pentrumateriale monocristaline.

(VWHGHUHPDUFDWFVHQVLELOLWDWHD6GHIDSWπ1SRDWHDYHDúLYDORULQHJDWLYHvQIXQF LHGHWLSXOGRSULLúLGHRULHQWDUHDD[HORUFULVWDOLQH

Varianta de traductor tensometric rezistiv metalic care s-a impus este ceaUHDOL]DWGLQIROLLPHWDOLFHGHRELFHLGLQFRQVWDQWDQ

3HQWUX PULUHD VHQVLELOLW LL VH XWLOL]HD] R VWUXFWXU FX PHDQGUH )ROLDPHWDOLF GH ÷5µPRE LQXW SULQ ODPLQDUH HVWH IL[DW FXXQ DGH]LYSHXQ VXSRUWL]RODWRU SROLPHULF6WUXFWXUD WLSLF D DFHVWXL WUDGXFWRU SRDWH IL XUPULW vQ ILJXUD2.193.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

15

Folieizolant

Foliemetalic( t t )

Terminale

Fig. 2.193 Structura traductorului tensometric rezistiv metalic.

$FHDVWFRQVWUXF LHFXQRVFXWVXEQXPHOHGHPDUFWHQVRPHWULFHVWHDSRLOLSLWDSOLFDWSHFRUSXODFUXLGHIRUPD LHVHGRUHúWHDILPVXUDW

$OWHYDULDQWHFRQVWUXFWLYHSRWILXUPULWHvQILJXUD

(a) (b) (c) (d)Fig. 2.1940UFLWHQVRPHWULFHDSHQWUXGLUHF LLOH°ESHQWUXGLUHF LLOH°,

FSHQWUXGLUHF LLOH°WLSUR]HWGSHQWUXPVXUDUHDSUHVLXQLL

7UDGXFWRDUHOHUH]LVWLYHWHQVRPHWULFHVHPLFRQGXFWRDUHVHUHDOL]HD]GHRELFHLGLQJHUPDQLXVDXVLOLFLX(OHSUH]LQWRVHQVLELOLWDWHVXSHULRDUFHORUPHWDOLFHGDUDX FRHILFLHQ L GH YDULD LH FX WHPSHUDWXUD PDL PDUL úL XQ GRPHQLX GH PVXU DOGHIRUPD LLORUFHYDPDLPLF

Fig. 2.195 Structura traductorului tensometric rezistiv semiconductor.

Cap.2 Rezistoare

16

De obicei traductoaUHOH WHQVRPHWULFH VH FRQHFWHD] vQ PRQWDMH WLS SXQWHSHQWUXPULUHDVHQVLELOLW LLúLFRPSHQVDUHDYDULD LLORUFXWHPSHUDWXUDÌQIXQF LHGHSUHFL]LDGRULWVHXWLOL]HD]SXQ LFXXQXOGRXVDXSDWUXWUDGXFWRDUH&RQHFWDUHDHOHFWULFDWHQVRUH]LVWRDUHORUODSXQWHDFXSDWUXWUDGXFWRDUHHVWHLGHQWLFFXFHDGLQILJXUDSUH]HQWDWODFDSLWROXO0DJQHWRUH]LVWRDUH

ÌQWDEHOXOVXQWSUH]HQWD LSULQFLSDOLLSDUDPHWULLDLXQRUWHQVRUH]LVWRDUHSURGXVHGH%/+(OHFWURQLFV,QFúL+RWWLQJHU%DOGZLQ0HDVXUHPHQWV,QF

Tabelul 2.26 Parametrii unor tensorezistoareSeria X

3URGXFWRUHBM

Seria Y3URGXFWRU

HBM

Seria traductoaremetalice

3URGXFWRU%/+

Seria traductoaresemiconductoare3URGXFWRU%/+

Tip tensorezistor metalic / folieconstantan

metalic/ folieconstantan

metalic/ folieconstantan

filamentsemiconductor

5H]LVWHQ DQRPLQDO5N (Ω)

120, 350, 700,1000

350 350-5000 120, 350, 1000,2000, 3000

7ROHUDQ D5N

(%)±0,3 ±0,3 ± (0,2 - 0,6) ±1, ±2

Sensibilitate S 2 2 2,05- 2,1 −110 ÷ +1507ROHUDQ 6

(%)±0,7 ±1,5 ±0,5 ±2

(ORQJD LDPD[LPµm/m)

50000 20000 >2250 5000

Domeniultemperaturilor de

utilizare

−70 ÷ +200°C −70 ÷ +200°C −75 ÷ +200°C −269 ÷ +372°C

3HQWUX UHDOL]DUHD FRPSHQVULL FX WHPSHUDWXUD SURGXFWRULL UHDOL]HD] FXDFHOHDúLPDWHULDOHúLFXVWUXFWXULVLPLODUHUH]LVWRDUHOLQLDUHIL[HFDUHQXVXQWVXSXVHGHIRUPD LLORUGDUSUH]LQWRYDULD LHFX WHPSHUDWXUDVLPLODU FX WHQVRUH]LVWRDUHOH3ULQWURJUXSDUHDGHFYDWvQVWUXFWXULGHWLSSXQWHHVWHSRVLELODVWIHOFRPSHQVDUHDYDULD LLORUUH]LVWHQ HLFXWHPSHUDWXUD