CAPITOLUL 2 REZISTOARE - CETTI · Conform celor expuse anterior rezistorul liniar fix, pe care-l vom numi ‡UH]LVWRU· UHSUH]LQW XQUH]LVWRUOLQLDUFXUH]LVWHQ DIL[5 FHQXSRDWHIL PRGLILFDW

CAPITOLUL 2

REZISTOARE

5H]LVWRUXOUHSUH]LQWRFRPSRQHQWHOHFWULFSDVLYGHWLSGLSROUHDOL]DW

vQVFRSXORE LQHULLXQHLLPSHGDQ HUH]LVWLYHFXRFRPSRUWDUHFkWPDLDSURSLDWGH

FHDLGHDOvQWUREDQGGHIUHFYHQ FkWPDLPDUHúLFRQFHQWUDWvQWUXQYROXPFkW

mai mic.3DUDPHWUXO IXQGDPHQWDO DO UH]LVWRUXOXL vO UHSUH]LQW UH]LVWHQ D HOHFWULF. În

DFHVWVHQVVHSRDWHGHILQLUH]LVWRUXOFDILLQGFRPSRQHQWDSDVLYUHDOL]DWvQVFRSXORE LQHULLXQHLUH]LVWHQ HHOHFWULFH

Din punct de vedere ideal, FHHDFHHVWHGHDOWIHOFRQVLGHUDWvQWURSULPID]vQSURLHFWDUHDFLUFXLWHORUHOHFWULFH UH]LVWRUXOHVWHFDUDFWHUL]DWQXPDLGH UH]LVWHQ DVD HOHFWULF GH XQGH úL GHQXPLUHD SUDFWLF LQFRUHFW a acestei componente de³UH]LVWHQ ´5H]LVWRUXOLGHDODUHRLPSHGDQ SXUUH]LVWLYZ 5FXLPSHGDQ DLQGHSHQGHQWGHIUHFYHQ DVHPQDOXOXLODFDUHIXQF LRQHD]úLFXWHQVLXQHDDSOLFDWODERUQHvQID]FXFXUHQWXOFHRSDUFXUJH

ÌQ UHDOLWDWHFDGHDOWIHORULFHFRPSRQHQW HOHFWULF VDXQHHOHFWULF FH HVWHFDUDFWHUL]DW GH DQXPL L SDUDPHWUL UHDOL UH]LVWRUXO YD DYHD R FRPSRUWDUH RLQIOXHQ PDLPDUHVDXPDLPLFGLIHULWGHFHDLGHDOGHSHQGHQWGHRVHULHGHfactori.

8QLWDWHD GH PVXU SHQWUX UH]LVWHQ D HOHFWULF HVWH 2KPXO Ω), careUHSUH]LQWUH]LVWHQ DHOHFWULFDXQXLHOHPHQWFRQGXFWRUFHDUHRFGHUHGHWHQVLXQHOD ERUQH GH 9 úL HVWH SDUFXUV GH XQ FXUHQW HOHFWULF FX LQWHQVLWDWHD GH $ ÌQSUDFWLF VH XWLOL]HD] DWkW PXOWLSOLL FkW úL VXEPXOWLSOL X]XDOL QRWD L FRQIRUPQRUPHORULQWHUQD LRQDOHFX

m=10-3 K=103

µ=10-6 M=106

n=10-9 G=109

p=10-12 T=1012

ÌQIXQF LHGHFDUDFWHULVWLFDHOHFWULFDGLFGHSHQGHQ DvQWUHWHQVLXQHDGHODERUQHOHUH]LVWRUXOXL úL FXUHQWXO HOHFWULF FH vO SDUFXUJH UH]LVWRDUHOH VH FODVLILF vQ GRX

categorii.• Rezistoare liniare FH DX RGHSHQGHQ OLQLDU vQWUH WHQVLXQH úL FXUHQW ILJXUD

2.1.a, numite simplu rezistoare.• Rezistoarele neliniare FH DX R FDUDFWHULVWLF WHQVLXQH ± FXUHQW QHOLQLDU

VSHFLILFSHQWUXILHFDUHWLSGHUH]LVWRUFHIDFHSDUWHGLQDFHDVWFDWHJRULHILJXUD2.1.b.

Cap. 2 Rezistoare

2

u

i i

u

a) liniar b) neliniarFig. 2.1&DUDFWHULVWLFDHOHFWULFDUH]LVWRDUHORU

$YkQGvQYHGHUHSRVLELOLWDWHDGHPRGLILFDUHDYDORULLUH]LVWHQ HLUH]LVWRUXOXLOLQLDUGHFWUHXWLOL]DWRUDFHVWHDVHvPSDUWvQGRXFODVH

• Rezistoare fixe, FDUH VXQW UHDOL]DWH vQ SURFHVXO GH IDEULFD LH SHQWUX R DQXPLWYDORDUHDUH]LVWHQ HLFHQXSRDWHILPRGLILFDWGHXWLOL]DWRUvQWLPSXOIRORVLULL

• Rezistoare variabile, la care utilizatorul poate modifica în mod continuuYDORDUHDUH]LVWHQ HLvQWUXQDQXPLW LQWHUYDO>5m, RM@VWDELOLWGHSURGXFWRU vQSURFHVXOGHIDEULFD LH

3HGHDOWSDUWHUH]LVWRDUHOHQHOLQLDUHVXQWUH]LVWRDUHDFURUUH]LVWHQ HVWHSXWHUQLFGHSHQGHQWGHXQDQXPLWSDUDPHWUXÌQDFHVWVHQVVHGLVWLQJ• termistoare±UH]LVWRDUHDFURUUH]LVWHQ HVWHGHSHQGHQWGHWHPSHUDWXU• varistoare ± UH]LVWRDUH D FURU UH]LVWHQ HVWH GHSHQGHQW GH WHQVLXQHD

HOHFWULFDSOLFDWODERUQH• magnetorezistoare UH]LVWRDUHDFURUUH]LVWHQ HVWHGHSHQGHQWGHFkPSXO

magnetic;• fotorezistoare UH]LVWRDUH D FURU UH]LVWHQ HVWH GHSHQGHQW GH IOX[XO

luminos;• tensorezistoareUH]LVWRDUHDFURUUH]LVWHQ HVWHGHSHQGHQWGHVROLFLWDUHD

PHFDQLF

)DFHP SUHFL]DUHD F DFHDVW FDWHJRULH GH UH]LVWRDUH QHOLQLDUH HVWH vQSHUPDQHQWGH]YROWDUHILLQGPHUHXGLYHUVLILFDW±DYkQGvQYHGHUHvQPRGGHRVHELWXWLOL]DUHDUH]LVWRDUHORUFDVHQ]RULHOHFWULFL8QVHQ]RUHOHFWULFVHUYHúWHvQJHQHUDOODFRQYHUVLDXQHLPULPLHOHFWULFHVDXQHHOHFWULFHvQWURDQXPLWPULPHHOHFWULFvQFD]XO QRVWUX UH]LVWHQ D&kWHYD GLQWUH VLPEROXULOH JUDILFH XWLOL]DWH SHQWUX GLIHULWHtipuri de rezistoare sunt prezentate în figura 2.2.

Sintetizând cele expuse anterior, din punct de vedere al principalelor criteriiGHFODVLILFDUHFDUHDXIRVWH[SXVHúLFDUHYRUILH[SXVHvQFRQWLQXDUHVHSUH]LQW vQILJXUDRFODVLILFDUHVXFFLQWDWLSXULORUGHUH]LVWRDUH

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

3

ο

ο

ο

ο

ο

ο

ο

ο

ο

t

ο

ο

u

e) d) c) b) a)

Fig. 2.2 Simboluri grafice pentru rezistoare.a) Simbol pentru rezistor fix; b) simbol tolerat pentru rezistor fix;

c) simbol pentru rezistor variabil; d) simbol pentru termistor; e) simbol pentru varistor.

Rezistoare

Neliniare

Variabile

Fixe

Liniare

Peliculare

Peliculare

Cu folie metalicã

plastic conductiv

peliculã metalicã

peliculã groasã

Cu folie metalicã

de oxizi metalici

peliculã groasã

peliculã metalicã VXE LUH

peliculã de carbon

Bobinate

Bobinate

De volum

carbon aglomerat carbon pirolitic

Tensorezistoare –UH]LVWHQ D GHSHQGHQW GH WHQVLXQHD PHFDQLF

Magnetorezistoare –UH]LVWHQ D GHSHQGHQW GH IOX[XO PDJQHWLF

Fotorezistoare –UH]LVWHQ D GHSHQGHQW GH IOX[XO OXPLQRV

Varistoare –UH]LVWHQ D GHSHQGHQW GH WHQVLXQH

Termistoare –UH]LVWHQ D GHSHQGHQW GH WHPSHUDWXU

Fig. 2.3 Clasificarea rezistoarelor.

Cap. 2 Rezistoare

4

2.1 Rezistoare (liniare) fixe

'HILQL LH&ODVLILFDUH

Conform celor expuse anterior rezistorul liniar fix, pe care-l vom numi³UH]LVWRU´ UHSUH]LQW XQ UH]LVWRU OLQLDU FX UH]LVWHQ D IL[ 5 FH QX SRDWH ILPRGLILFDWGHXWLOL]DWRU

Principala clasificare a acestor rezistoare o constituie modul tehnologic derealizare a elementului rezistiv; din acest punct de vedere se pot clasifica în:• rezistoare bobinate, DOFURUHOHPHQW UH]LVWLY HVWH UHDOL]DWSULQERELQDUHDXQXL

FRQGXFWRUGHvQDOWUH]LVWLYLWDWHSHXQVXSRUWGLHOHFWULF• rezistoare peliculareDOFURUHOHPHQW UH]LVWLYHVWHRSHOLFXO UH]LVWLYGHSXV

printr-un procedeu tehnologic specific pe un suport dielectric;• UH]LVWRDUH FX IROLH PHWDOLF DO FURU HOHPHQW UH]LVWLY HVWH R IROLH PHWDOLF

GHSXVSHXQVXSRUWGLHOHFWULF• rezistoare de volum, când elementul rezistiv al rezistorului este de forma unei

PDVH FRPSDFWH VXE R DQXPLW IRUP RE LQXW SULQ DPHVWHFXO XQHL SXOEHULPHWDOLFH GH vQDOW UH]LVWLYLWDWH FX XQ OLDQW GH OHJWXU (OHPHQWXO UH]LVWLYconstituie componenta ca atare.

&HOH PDL XWLOL]DWH vQ HOHFWURQLF GLQWUH DFHVWHD VXQW UH]LVWRDUHOH SHOLFXODUH FDUHSUH]LQW DYDQWDMXO XQRU GLPHQVLXQL PLFL D XQRU SDUDPHWUL EXQL GH]YROWDUHDDFHVWRUD ILLQG FRQWLQX DMXQJkQGXVH OD SDUDPHWULL DFWXDOL JUHX GH LPDJLQDW FXPXOWWLPSvQXUP

(YROX LD vQ WLPS D UH]LVWRDUHORU FD GH DOWIHO D WXWXURU FRPSRQHQWHORUHOHFWURQLFHDIRVWvQFRQFRUGDQ FXHYROX LDHOHFWURQLFLLÌQHOHFWURQLFVDXUPULWvQJHQHUDORFUHúWHUHDIUHFYHQ HLGHOXFUXDFLUFXLWHORUSHQWUXDUVSXQGHFkWPDLELQH OD R IXQF LRQDUH D DFHVWRUD vQ WLPS UHDO SUHFXP úL SHQWUX D VH DVLJXUDFLUFXLWHORU UHDOL]DWH R FUHúWHUH D ILDELOLW LL úL UH]LVWRDUHOH DX IRVW QHYRLWH VVDWLVIDF DQXPLWH FHULQ H IXQF LRQDOH ,QGLIHUHQW FkW GH EXQH DU IL IRVW FLUFXLWHOHLQWHJUDWH GH VXSHUFODV 9/6, 0&0 HWF HOH QX SRW IXQF LRQD OD SDUDPHWULLSURLHFWD L IU D DYHD vQ YHGHUH úL FRPSRQHQWHOH SDVLYH vQJOREDWH vQ VWUXFWXUDmodulului electronic.

$YkQGvQYHGHUHXOWLPHOHHYROX LLDOHFRPSRQHQWHORUDFWLYHFHOHSHED]GH*D$VFDUHDXIUHFYHQ HGHIXQF LRQDUHGHRUGLQXO*+]vQPXOWHVLWXD LLSUREOHPDHVHQ LDODXWLOL]ULLDFHVWRUFRPSRQHQWHDGHYHQLWIUHFYHQ DODFDUHSRWILXWLOL]DWHcomponentele pasive în general.

5H]LVWRDUHOHSRWILGHDVHPHQHDFODVLILFDWHvQIXQF LHGHYDORDUHDUH]LVWHQ HLSXWHULLQRPLQDOHWHQVLXQLLQRPLQDOHIUHFYHQ DPD[LPGHXWLOL]DUHWROHUDQ WLSXOterminalelor.


5

&DUDFWHULVWLFLOHúLPDUFDUHDUH]LVWRDUHORU

ÌQ DIDUD PULPLORU FDUDFWHULVWLFH FRPXQH WXWXURU FRPSRQHQWHORU SDVLYHSUH]HQWDWH vQ FDSLWROXO UH]LVWRDUHOHPDLSUH]LQW úL DO L SDUDPHWULL VSHFLILFL&XFkW IDEULFDQWXO GH FRPSRQHQWH SXQH OD GLVSR]L LD XWLOL]DWRUXOXL LQIRUPD LL PDLDPSOHSULYLWRDUHODFRPSRUWDUHDHOHFWULFúLQHHOHFWULFDFRPSRQHQWHORUSDVLYHFXDWkW HVWH SRVLELO FD GLQ PXOWLWXGLQHD GH FRPSRQHQWH H[LVWHQWH V VH DGRSWHUH]LVWRUXOFXSHUIRUPDQ HOHRSWLPHFRUHVSXQ]WRDUHXQHLDQXPLWHDSOLFD LL

5H]LVWHQ DQRPLQDO5N [Ω],UHSUH]LQWYDORDUHDUH]LVWHQ HLFHVHGRUHúWHDVHRE LQHvQSURFHVXOGHIDEULFD LHúLHVWHPDUFDWvQJHQHUDOSHFRUSXOUH]LVWRUXOXL6HPVRDU vQ FXUHQW FRQWLQXX OD WHPSHUDWXUD GH UHIHULQ θ0, (20°C sau 25°C).Valorile nominale sunt conform seriilor de valori EnYH]LSDUDJUDIXOúLDQH[D$1.1.

Domeniul valorilor nominale, [RNm, RNM] UHSUH]LQW LQWHUYDOXOPD[LP vQcare sunt incluse valorile nominale pentru un anumit tip de rezistor produs de oDQXPLW ILUP 9DORULOH X]XDOH VXQW FXSULQVH vQ LQWHUYDOXO Ω ... 10MΩ; suntUHDOL]DWH vQV úL UH]LVWRDUH GH YDORDUH IRDUWH PLF SkQ OD PΩ SUHFXP úL GHUH]LVWHQ IRDUWHPDUHSkQOD7Ω.

7ROHUDQ DWGHIDEULFD LHHVWHDEDWHUHDUHODWLYPD[LPDYDORULLUHDOHDUH]LVWHQ HL ID GHYDORDUHDQRPLQDO5H]LVWRDUHOHDXWROHUDQ HVLPHWULFH ILLQG vQmod frecvent de la ± 0,1% la ±YDORDUHDPLQLPSRDWHILGH± 0,0005%. SeGHWHUPLQFRQIRUPUHOD LLORUSUH]HQWDWHvQSDUDJUDIXO

7ROHUDQ H GDWRUDWH GLYHUúLORU IDFWRUL Wj , H[SULP DEDWHUHD UH]LVWHQ HL ODDF LXQHDGLYHUúLORUIDFWRULHOHFWULFLúLQHHOHFWULFLYH]LUHOD LD

7ROHUDQ D JOREDO Wg UHSUH]LQW DEDWHUHDPD[LP WRWDO D YDORULL UHDOH DUH]LVWHQ HLID GHFHDQRPLQDOFHSRDWHVDSDUvQWLPSXOIXQF LRQULLUH]LVWRUXOXLvQDQXPLWHFRQGL LLUHDOHGHIXQF LRQDUH6HGHWHUPLQFXUHOD LD

Clasa de stabilitateH[SULPDEDWHUHDPD[LPDYDORULLUH]LVWHQ HLUH]XOWDWvQXUPDXQRUvQFHUFULVSHFLILFHGHOXQJúLVFXUWGXUDWODGLIHUL LIDFWRULHOHFWULFLúLQHHOHFWULFL(VWHGHDOWIHOXQDOWPRGGHDSUH]HQWDDEDWHULOHWj .

Domeniul temperaturilor de utilizare, [θm,θM], UHSUH]LQW LQWHUYDOXOPD[LPGHWHPSHUDWXUvQFDUHSRDWHILXWLOL]DWUH]LVWRUXO

Temperatura punctului fierbinte (hot spot), θpf, UHSUH]LQW WHPSHUDWXUDPD[LP OD FDUH SRDWH DMXQJH FHO PDL ILHUELQWH SXQFW GLQ LQWHULRUXO UH]LVWRUXOXL5H]LVWRDUHOH VXQW FRPSRQHQWH SDVLYH GLVLSDWLYH GLVLSkQG SUDFWLF WRDW SXWHUHDHOHFWULFODFDUHVXQWVROLFLWDWH3XWHUHDHVWHGHIDSWGLVLSDWGHHOHPHQWXOUH]LVWLYLDUGHODDFHVWDVHWUDQVPLWHSULQFRQGXF LHWHUPLFODVXSUDID DUH]LVWRUXOXLGHXQGHmai ales la componentele din tehnologia THT (Through Hole Tehnology) prinFRQYHF LHVHWUDQVPLWHFWUHPHGLXODPELDQW'HFLWHPSHUDWXUDFHDPDLULGLFDWRare elementul rezistiv, iar maximul temperaturii elementului rezistiv este în generalîn centrul lui, aceasta constituind θpf. La orice tip de rezistor temperatura punctului

Cap. 2 Rezistoare

6

ILHUELQWHHVWHPDLPDUHGHFkWWHPSHUDWXUDPD[LPGHXWLOL]DUHθM'LIHUHQ Dθpf-θM

HVWH GHSHQGHQW GH UH]LVWHQ D WHUPLF GH FRQGXF LH GH OD HOHPHQWXO UH]LVWLY ODVXSUDID D UH]LVWRUXOXL $FHDVWD VH SRDWH DSUR[LPD FD ILLQG HJDO FX FHD DHOHPHQWXOXL GH SURWHF LH /D UH]LVWRDUHOH SHOLFXODUH OFXLWH GLIHUHQ D θpf-θM estePLFUH]LVWHQ DWHUPLFGHFRQGXF LHDORFXOXLHVWHPLFúLVHSRDWHDSUR[LPDvQSUDFWLF θpf ≅ θM. La rezistoarele bobinate în corp ceramic θpf>>θM GDWRULWUH]LVWHQ HL WHUPLFHGHFRQGXF LH ULGLFDW DHOHPHQWXOXL UH]LVWLY'HH[HPSOX VXQWrezistoare bobinate ce au θM =200°&úLθpf = 400°C.

&DWHJRULDFOLPDWLF11/N2/N3,H[SULPFRQGL LLOHFOLPDWLFHODFDUHWUHEXLHYHULILFDWXQUH]LVWRUGHFWUHSURGXFWRU

Domeniul temperaturilor de depozitare, [θdm,θdM], UHSUH]LQW LQWHUYDOXOPD[LPGHWHPSHUDWXUvQFDUHSRDWHILGHSR]LWDWRYUHPHvQGHOXQJDWXQUH]LVWRU

&RHILFLHQWXO GH YDULD LH FX WHPSHUDWXUDαθ [ppm/°C] H[SULP DEDWHUHDYDORULLUH]LVWHQ HLODYDULD LDWHPSHUDWXULLFRUSXOXLVXFX°C.

ÌQ IXQF LH GH WLSXO HOHPHQWXOXL UH]LVWLY UH]LVWRDUHOH SRW DYHD FRHILFLHQ LSR]LWLYL QHJDWLYL VDXR DQXPLW DEDWHUH vQ MXUXO OXL ]HUR GHFL GH IRUPD±α. Dinacest punct de vedere, rezistoarele au evaluat foarte mult, ajungându-se la uncoeficient de ±1ppm/°C.

&RHILFLHQWXO GH YDULD LH FX WHQVLXQHD αU [ppm/V] H[SULP DEDWHUHDUH]LVWHQ HLODYDULD LDWHQVLXQLLGHODERUQHOHUH]LVWRUXOXLFX9

7HQVLXQHD WHUPRHOHFWULF 8k UHSUH]LQW WHQVLXQHD FRQWLQX FH DSDUH ODERUQHOHUH]LVWRUXOXLGDWRULWGLIHUHQ HLGHWHPSHUDWXUGLQWUHWHUPLQDOH

5H]LVWHQ DGH L]ROD LH5iz,HVWH UH]LVWHQ DGLQWUH WHUPLQDOHOH UH]LVWRUXOXL úLcorpul acestuia.

7HPSHUDWXUDQRPLQDOθN, este temperatura mediului ambiant la care seGHWHUPLQGHILQHúWHSXWHUHDQRPLQDO

3XWHUHD QRPLQDO 3N [W] UHSUH]LQW SXWHUHDPD[LP SH FDUH SRDWH V RGLVLSH UH]LVWRUXO OD R IXQF LRQDUH FRQWLQX vQWUXQPHGLX DPELDQW FX WHPSHUDWXUDHJDOFXFHDQRPLQDOYH]LSDUDJUDIXO3XWHULOHQRPLQDOHQXVXQWvQJHQHUDOVWDQGDUGL]DWHLQWHUQD LRQDOvQWkOQLQGXVHGLYHUVHYDORULFHSRWGLIHULGHODRILUP

OD DOWD SHQWUX DFHODúL WLS GH UH]LVWRU &kWHYD YDORUL VXQW : : :0,25W; 0,33W; 0,4W; 0,5W; 0,6W; 0,75W; 1W; 2W; 3W; etc.

&RHILFLHQWXO GH GLVLSD LH ' UHSUH]LQW SXWHUHD HYDFXDW GH UH]LVWRU ODmodificarea temperaturii corpului cu 1°C sau K.

5H]LVWHQ D WHUPLF 5th, [K/W sau °C/W] este inversul coeficientului deGLVLSDUH H[SULPkQG YDULD LD WHPSHUDWXULL FRPSRQHQWHL OD HYDFXDUHD FWUHPHGLXOambiant a unei puteri de 1W.

3XWHUHD WHUPLF PD[LP DGPLVLELO 3Aθ, HVWH SXWHUHD PD[LP SH FDUHSRDWH V R GLVLSH XQ DQXPLW WLS GH UH]LVWRU vQ IXQF LH GH WHPSHUDWXUD PHGLXOXLDPELDQWvQFDUHIXQF LRQHD]

3XWHUHDPD[LPDGPLVLELO3A UHSUH]LQWSXWHUHDPD[LP ODFDUHSRDWHILVROLFLWDWvQFUFDWXQDQXPLWWLSGHUH]LVWRUvQWLPSXOIXQF LRQULL


7

7HQVLXQHDQRPLQDO8NUHSUH]LQWYDORDUHDPD[LP D WHQVLXQLLFRQWLQXHFHSRDWHILDSOLFDWODERUQHOHXQXLUH]LVWRULQGLIHUHQWGHYDORDUHDUH]LVWRUXOXLODRIXQF LRQDUH vQGHOXQJDW (VWH OLPLWDW GLQ PRWLYH GH VWUSXQJHUH GLHOHFWULF DSU LORUFRQVWLWXHQWHL]RODWRDUH

7HQVLXQHDPD[LPDGPLVLELO8AHVWHYDORDUHDPD[LPDWHQVLXQLLODFDUHSRDWHILVROLFLWDWXQUH]LVWRUvQWLPSXOIXQF LRQULL

5H]LVWHQ DFULWLF5cr,UHSUH]LQWYDORDUHDUH]LVWHQ HLSHQWUXXQDQXPLWWLSGH UH]LVWRU FX R DQXPLW WLSRGLPHQVLXQH UH]LVWRU FH SRDWH IL XWLOL]DW VLPXOWDQ ODSXWHUHDQRPLQDOúLWHQVLXQHDQRPLQDO

Factorul de zgomot, F [µV/V sau dB],UHSUH]LQWUDSRUWXOGLQWUHWHQVLXQHDGH ]JRPRW D UH]LVWRUXOXL úL WHQVLXQHD FRQWLQX GH 9 FH HVWH DSOLFDW OD ERUQHOHsale.

,QGXFWDQ D SDUD]LW /p FRQVWLWXLH LQGXFWDQ D QHGRULW D UH]LVWRUXOXL FHGHSLQGHvQPRGGHRVHELWGHVWUXFWXUDFRQVWLWXWLY

&DSDFLWDWHD SDUD]LW &p, HVWH FDSDFLWDWHD QHGRULW D UH]LVWRUXOXLGHSLQ]kQGGHVROX LDFRQVWLWXWLYúLGHWLSXOPDWHULDOHORUL]RODWRDUHXWLOL]DWH

&RQGL LL GH OLSLUH VSHFLILF WHPSHUDWXUDPD[LP úL WLPSXOPD[LP SHQWUXOLSLUHD UH]LVWRUXOXL SH FDEODMXO LPSULPDW 3HQWUX WHUPLQDOHOH SHQWUX LQVHU LH VHVSHFLILFúLOXQJLPHDPLQLPDWHUPLQDOHORU

Marcarea rezistoarelor

Ca la orice comSRQHQW SDVLY GLQPRWLYH GH VLPSOLILFDUH D FRGXULORU SHFRUSXO FRPSRQHQWHORU VXQW LQVFULS LRQD L R SDUWH GLQ SDUDPHWULL DFHVWRUD 6H SRWPDUFD XWLOL]kQG FRGXUL VSHFLILFH UH]LVWHQ D QRPLQDO WROHUDQ D FRHILFLHQWXO GHYDULD LHFXWHPSHUDWXUDSXWHUHDQRPLQDO UDWDGHGHIHFWDUH&RGXULOHGHPDUFDUHVXQWvQJHQHUDOVWDQGDUGL]DWHLQWHUQD LRQDOGDUSRWILvQWkOQLWHúLFRGXULVSHFLILFHGHILUPúLSHQWUXvQOWXUDUHDHYHQWXDOHORUDPELJXLW LFHSRWVDSDUHVWHLQGLFDWFDSHQWUXILHFDUHWLSGHFRPSRQHQWVILHFRQVXOWDWFDWDORJXOILUPHLXQGHHVWHH[SXVmodul de marcare.

5H]LVWHQ DQRPLQDO5N, HVWHPDUFDW SH FRUSXO RULFUXL UH]LVWRU XQHRULILLQGPDUFDW QXPDL DFHVW SDUDPHWUX 6H XWLOL]HD] FRGXUL DOIDQXPHULFH úL FRGXOculorilor.

Codurile alfanumerice au mai multe variante.Cod alfanumeric – varianta 1. Rezistoarele cu valori de ordinul ohmilor,

GHFLFXUH]LVWHQ DQRPLQDOPDLPLFGHFkWΩVHPDUFKHD] vQ³FODU´DGLFFLIUHOH VHPQLILFDWLYHFXYLUJXODSXV vQPRG FRUHVSXQ]WRU IU D VH LQVFULS LRQDsimbolul Ω. Pentru valori nominale RN ≥ 1KΩVHPDUFKHD]FLIUHOHVHPQLILFDWLYHiar în locul virgulei se pune simbolul de multiplicare, K ori M, în modFRUHVSXQ]WRUÌQWDEHOXOVXQWSUH]HQWDWHFkWHYDH[HPSOH

Cap. 2 Rezistoare

8

Tabelul 2.1 Marcarea în cod alfanumeric 1.Marcare 2,2 62 1K2 1K 1M 1M8RN[Ω] 2,2 62 1200 1000 106 1,8⋅106

Cod alfanumeric – varianta 2.(VWHDVHPQWRUFXFHOSUH]HQWDWDQWHULRUFXGLIHUHQ DFSHQWUX5N <999Ω, în locul virgulei se pune litera R, deci RN =2,2Ω,YDILPDUFDW5LDU5N=62ΩYDILPDUFDW5

Cod alfanumeric – varianta 3,XWLOL]DWSHQWUXUH]LVWRDUH60'VXEIRUPGHFKLS OD FDUH VH PDUFKHD] GRDU YDORDUHD QRPLQDO D UH]LVWHQ HL GDWRULWdimensiunilor mici).

Codul este format din cifrele semnificative ale rezistHQ HLQRPLQDOHOLWHUD5SXV vQ ORFXOYLUJXOHLSHQWUXYDORULPLFL DOH UH]LVWHQ HL úLRUGLQXOGHPXOWLSOLFDUHSXWHUHDOXL]HFHSHQWUXYDORULPDULDOHUH]LVWHQ HL

3HQWUX WROHUDQ H GH ±20%, ±10% úL ±5% ILLQG QHFHVDUH GRX FLIUHsemnificative codul folosit este de forma:

Rxy, pentru RN < 1Ω.xRy, pentru RN = 1Ω... 9,1ΩxyR, pentru RN = 10Ω…99Ωxym, pentru RN ≥ 100Ω.

unde:[HVWHSULPDFLIUVHPQLILFDWLY\HVWHDGRXDFLIUVHPQLILFDWLYm este ordinul de multiplicare.

3HQWUX WROHUDQ HPLFL GH±2,5%, ±2% úL±1%, etc. fiind necesare trei cifresemnificative codul folosit este de forma:

Rxyz, pentru RN < 1Ω.xRyz, pentru RN = 1Ω…9,99ΩxyRz, pentru RN = 10Ω…99,9ΩxyzR, pentru RN = 100Ω…999Ωxyzm, pentru RN ≥ 1000Ω.În tabelul 2.2. sunt prezentate câteva exemple de marcare.

Tabelul 2.2 Marcarea rezistoarelor SMD chip.Marcare 1R2 51R 681 913 1R62 26R7 1781 4873RN[Ω] 1,2 51 680 91⋅103 1,62 26,7 1780 487⋅103

Cod alfanumeric - varianta 4. Pentru rezistoare SMD de dimensiune foartePLF VH XWLOL]HD] XQ FRG DOIDQXPHULF FRQIRUP WDEHOHORU úL FRG(,$[29].


9

Tabelul 2.3 Cod numeric pentru cifrele semnificative.Code Valoare Code Valoare Code Valoare Code Valoare010203040506070809101112131415161718192021222324

100102105107110113115118121124127130133137140143147150154158162165169174

252627282930313233343536373839404142434445464748

178182187191196200205210215221226232237243249255261267274280287294301309

495051525354555657585960616263646566676869707172

316324332340348357365374383392402412422432442453464475487499511523536549

737475767778798081828384858687888990919293949596

562576590604619634649665681698715732750768787806825845866887909931953976

Tabelul 2.4 Cod literal pentru multiplicator.Cod literal S R A B C D E FMultiplicator 10-2 10-1 100 101 102 103 104 105

&RGXO VH XWLOL]HD] SHQWUX WROHUDQ H GH ±0,1%, ±0,5%, ± $FHDVWPDUFDUHID GHYDULDQWDDQWHULRDUFRGDOIDQXPHULFYDULDQWDUHGXFHPDUFDUHDFXXQGLJLW'HH[HPSOXGDFHVWHPDUFDWSHUH]LVWRU&UH]XOW5N=12,4 kΩ.

Codul culorilor este prezentat în tabelul 2.5.

Cap. 2 Rezistoare

10

Tabelul 2.5 Codul culorilorCuloare &LIU

VHPQLILFDWLYMultiplicator 7ROHUDQ

(%)Coeficientul deYDULD LHFX

temp. (ppm/°C)Negru 0 1 - ±250Maro 1 10 ±1 ±1005RúX 2 102 ±2 ±50Portocaliu 3 103 - ±15Galben 4 104 - ±25Verde 5 105 ±0,5 ±20Albastru 6 106 ±0,25 ±10Violet 7 107 ±0,1 ±5Gri 8 108 ±0,05 ±1Alb 9 109 -Auriu - 10-1 ±5 -Argintiu - 10-2 ±10 ±200)UFXORDUH - ±20

8WLOL]kQG FRGXO FXORULORU VH SRDWH PDUFD UH]LVWHQ D QRPLQDO WROHUDQ DFRHILFLHQWXO GH YDULD LH FX WHPSHUDWXUD úL XQHRUL ILDELOLWDWHD 3HQWUX PDUFDUHDUH]LVWHQ HL QRPLQDOH vQ IXQF LH GH WROHUDQ VXQW QHFHVDUH GRX VDX WUHL FLIUHVHPQLILFDWLYHGXSFXPVDSUH]HQWDWDQWHULRUWROHUDQ DúLFRHILFLHQWXOGHYDULD LHFX WHPSHUDWXUDSRW ILPDUFDWH VDXQHPDUFDWH5H]XOWSRVLELOLW LOHGHPDUFDUH vQcodul culorilor prezentate în figura 2.4.

1 2 3 m t α

1 2 m

a)

1 2 m t

b)

1 2 3 m t

c)

1 2 m t α

f)e)

d)

12 3 m t

αλ

Fig. 2.4 Marcarea rezistoarelor în codul culorilor. SULPD FLIU VHPQLILFDWLY D GRXD FLIU VHPQLILFDWLY D WUHLD FLIU VHPQLILFDWLY

P ± PXOWLSOLFDWRU W ± WROHUDQ D α FRHILFLHQW GH WHPSHUDWXU λ - fiabilitate.


11

2UGLQHDGHFLWLUHDFXORULORUHVWHGHODFDSWXOFHOPDLDSURSLDWYH]LILJXUDDúLEVDXXOWLPDFXORDUHHVWHGHDSUR[LPDWLYGRXRULPDLODWGHFkWFHOHODOWHYH]L ILJXULOH F G H I 0DUFDUHD GLQ ILJXUD D HVWH XWLOL]DW SHQWUXUH]LVWRDUHFXWROHUDQ HGH±FkQGVHPDUFKHD]QXPDLUH]LVWHQ DQRPLQDOFXtrei inele colorate, RN=C1C2mΩGHH[HPSOXILLQGPDUFDWHFXORULOHURúX&1URúX(C2SRUWRFDOLXPUH]XOW5N= 22⋅103 Ω= 22KΩ.

0DUFDUHD GLQ ILJXUD E HVWH XWLOL]DW SHQWUX UH]LVWRDUH FX WROHUDQ GH± úL± IU V VHPDUFKH]H FRHILFLHQWXO GH YDULD LH FX WHPSHUDWXUD FXPVXQW GH H[HPSOX UH]LVWRDUHOH FX SHOLFXO GH FDUERQ ÌQ DFHVW FD] VH PDUFKHD]UH]LVWHQ D QRPLQDO FXORULOH &1, C2 P úL WROHUDQ D 'H H[HPSOX ILLQGPDUFDWHFXORULOH URúX &1), galben (C2PDUR P úL DXULX UH]XOW 5N=24⋅10Ω=240Ω cuWROHUDQ D W ± 0DUFDUHD GLQ ILJXUD F HVWH XWLOL]DW SHQWUX PDUFDUHDUH]LVWHQ HLQRPLQDOHúLDWROHUDQ HLWROHUDQ DILLQGPDLPLFGHFkW±2,5%. În acestFD] DSDUH FD QHFHVDU D WUHLD FLIUD VHPQLILFDWLY &3 &RHILFLHQWXO GH YDULD LH FXWHPSHUDWXUDDWXQFLFkQGHVWHPDUFDWHVWHXOWLPDFXORDUHYH]LILJGúLHVDXXQpunct colorat, conform figurii 2.4.f.

7ROHUDQ D WSRDWH ILPDUFDW vQ FRGUXO FXORULORU FRQIRUPPRGXOXL H[SXVPDLVXVvQ³FODU´FXVDXIUVLPEROXOúLvQFRGOLWHUDOFRQIRUPWDEHOXOXL

Tabel 2.6&RGXOOLWHUDOSHQWUXPDUFDUHDWROHUDQ HLUH]LVWRDUHORUCodliteral

L P W B C D F G H J K M

t(%) ±0,01 ±0,02 ±0,05 ±0,1 ±0,25 ±0,5 ±1 ±2 ±2,5 ±5 ±10 ±20

Exemplu, având un rezistor pe care este marcat, 1K K

UH]XOW5N=1KΩúLWROHUDQ DW ±10%.

&RHILFLHQWXOGHYDULD LHFXWHPSHUDWXUD VHPDUFKHD] vQFRGXOFXORULORUYH]LILJXUDVDXvQFRGOLWHUDO3HQWUXUH]LVWRDUHOHFXVWUDWXULJURDVHVHIRORVHúWHa pentru ±50 ppm/°C, b pentru ±100 ppm/°C, c pentru ±250 ppm/°C.

3XWHUHDQRPLQDO3NVHPDUFKHD]vQFODUODUH]LVWRDUHOHERELQDWH8QHRULSH FRUSXO UH]LVWRUXOXL SRDWH IL PDUFDW úL FRGXO DFHVWXLD PDL UDU HYHQWXDO ODUH]LVWRDUHGHGLPHQVLXQHPDUH&DRULFHFRPSRQHQWUH]LVWRDUHOHSUH]LQWXQFRGFDUH HVWH VSHFLILF ILUPHL SURGXFWRDUH $FHVWH FRGXUL VXQW DOIDQXPHULFH 3DUWHDOLWHUDOHVWHGHSHQGHQWvQJHQHUDOGHWLSXOHOHPHQWXOXLUH]LVWLYLDUSDUWHDQXPHULFGH WLSRGLPHQVLXQH SXWHUHD QRPLQDO úL GH WLSXO WHUPLQDOHORU DYkQG vQ YHGHUHPRGXO GH FRQWDFWDUH DO DFHVWRUD DWkW OD HOHPHQWXO UH]LVWLY FkW úL OD FDEODMXOimprimat.

Cap. 2 Rezistoare

12

Exemple5&*±UH]LVWRUFXSHOLFXOGHFDUERQFXSXWHUHDQRPLQDOGH:FXWHUPLQDOHD[LDOH5%&±UH]LVWRUERELQDWFLPHQWDWFXSXWHUHDQRPLQDOGH3W.

6WUXFWXUDFRQVWUXFWLYJHQHUDODUH]LVWRDUHORU

6XEIRUPDFHDPDLJHQHUDOXQ UH]LVWRU IL[SUH]LQW VWUXFWXUDSUH]HQWDW vQfigura 2.5.

Terminal

=RQ de

contactare

Element rezistiv

=RQ de

contactare

Terminal

Suport dielectric

(OHPHQWGHSURWHF LH

Fig. 2.56WUXFWXUDFRQVWUXFWLYJHQHUDODUH]LVWRUXOXL

([FHS LDGHODVWUXFWXUDSUH]HQWDWRUHSUH]LQWUH]LVWRDUHOHGHYROXPODFDUHQXVHXWLOL]HD]VXSRUWXOGLHOHFWULF

Elementul rezistiv UHSUH]LQW FRPSRQHQWD FRQVWLWXHQW HVHQ LDO DUH]LVWRUXOXLGHFDUHGHSLQGDSURDSHWR LSDUDPHWULLUH]LVWRUXOXL

0DWHULDOHOH XWLOL]DWH OD UHDOL]DUHD HOHPHQWXOXL UH]LVWLY WUHEXLH V ILHFDUDFWHUL]DWHSULQUH]LVWLYLWDWHULGLFDWFRHILFLHQWXOGHWHPSHUDWXU úLWHQVLXQHDOUH]LVWLYLW LL FkW PDL PLF WHQVLXQH HOHFWURPRWRDUH vQ UDSRUW FX FXSUXO FkW PDLVF]XW WHPSHUDWXU ULGLFDW GH WRSLUH R EXQ DGHUHQ OD VXSRUWXO GLHOHFWULF$FHVWRU FHULQ H OH FRUHVSXQG vQWURPVXUPDLPDUH VDXPDLPLFPDWHULDOH FDDOLDMHSHED]GHFXSUXQLFKHOFURPFREDOWPDQJDQILHUR[L]LPHWDOLFL±&U6L2SnO2; carbonul, etc.

ÌQ IXQF LH GH PRGXO WHKQRORJLF úL WLSXO PDWHULDOHORU XWLOL]DWH OD UHDOL]DUHDHOHPHQWXOXLUH]LVWLYUH]XOWúLWLSXULOHGHUH]LVWRDUHÌQDFHVWVHQVVHGLVWLQJ• Element rezistiv bobinat RE LQXW SULQ ERELQDUHD XQXL FRQGXFWRU GH vQDOW

rezistivitate pe un suport dielectric cilindric.• Element rezistiv pelicular, care poate fi,- SHOLFXOGHFDUERQRE LQXWSULQSLUROL]FXRJURVLPHGHµm;- SHOLFXO PHWDOLF GHSXV SULQ SULQWUXQ SURFHGHX VSHFLILF FX R JURVLPH GH

0,01...0,1 µm;- SHOLFXOGLQR[L]LPHWDOLFLGHSXVSULQKLGUROL]FXRJURVLPHGH«µm;


13

- SHOLFXOJURDVQXPLWúLJOD]XUPHWDOLFVDXSHOLFXOFRPSR]LWGHSXVSULQserigrafie, cu o grosime de 15 … 30µm;

• EOHPHQWUH]LVWLYVXEIRUPGHIROLHPHWDOLF.• Element rezistiv de volum VXE IRUPD XQHL PDVH FRPSDFWH RE LQXWH SULQ

SUHVDUHD VDX H[WUXGDUHD XQXL DPHVWHF IRUPDW GLQWUXQ PDWHULDO FRQGXFWLY úLOLDQWGHOHJWXU

O mare parte din parametrii rezistorului depind în exclusivitate de elementulUH]LVWLYUH]LVWHQ DQRPLQDOWROHUDQ HOHWWj, tg; clasa de stabilitate, coeficientul deYDULD LH FX WHPSHUDWXUD úL WHQVLXQHD ]JRPRWXO GRPHQLXO WHPSHUDWXULORU GHXWLOL]DUH HWF0DLPXOW VDXPDL SX LQ GHSLQG úL SXWHUHD QRPLQDO WHPSHUDWXUDPD[LP HOHPHQWHOH SDUD]LWH /p, Cp IRUPD HOHPHQWXOXL UH]LVWLY $FHDVWGHSHQGHQ YDILH[SOLFDWvQSDUDJUDIHOHXUPWRDUH

În tabelul 2.7. sunt prezentate câteva caracteristici pentru câteva materialeutilizate la realizarea rezistoarelor.

Tabelul 2.7 Caracteristici ale unor materiale rezistive, [6], [7].$OLDMFRPSR]L LH&DUDFWHULVWLF

ManganinNi-4%Cu-84%Mn-12%

ConstantanNi-45%Cu-55%

KanthalFe-75%Cr-20%Al-4,5%Co-0,5%

NikrothalNi-75%Cr-17%Mn,Si-8%

Crom-nichelNi-80%Cr-20%

Rezistivitate(Ωmm2/m)

0,42 0,5 1,35 1,33 1,15

Coeficientul detemp.(ppm/°C)

±15 ±20 ±20 ±20 130

TemperaturaPD[LP GHutilizare (°C)

100 535 150 230 1000

Tensiunetermoelectro-PRWRDUH ID GHcupru µv/°C

2 43 3,5 2 -

Suportul dielectricQXPLWúLL]RODQWDUHSUDFWLFUROXOGHVXV LQHUHPHFDQLFD HOHPHQWXOXL UH]LVWLY 6H UHDOL]HD] GLQ PDWHULDOH L]RODWRDUH FDUH WUHEXLH VSUH]LQWH R UH]LVWLYLWDWH FkW PDL ULGLFDW SHUPLWLYLWDWH GLHOHFWULF FkW PDL PLFSLHUGHUL FkWPDL UHGXVH ULJLGLWDWH GLHOHFWULF FkWPDL ULGLFDW 7UHEXLH V ILH EXQconductor termic, nehigroscopic, rezistent mecanic. Pentru rezistoarele, peliculare,WUHEXLH V SHUPLW R FkW PDL EXQ DGHUHQ D SHOLFXOHL UH]LVWLYH OD VXEVWUDW 6H

Cap. 2 Rezistoare

14

XWLOL]HD]SUHGRPLQDQWPDWHULDOHFHUDPLFHUH]LVWRDUHSHOLFXODUHúLERELQDWHILEUGHVWLFOUH]LVWRDUHERELQDWHDOXPLQQLWUXUGHDOXPLQLXEHULOLD 2SDUWHGLQSDUDPHWULLUH]LVWRUXOXLVXQWLQIOXHQ D LGe suportul dielectric. ÎnDFHVW VHQV WHQVLXQHD QRPLQDO HVWH GHSHQGHQW GH WLSXO PDWHULDOXOXL ULJLGLWDWHDGLHOHFWULF úL GLPHQVLXQLOH VXSRUWXOXL 3DUDPHWULL WHUPLFL 3N, D, τth, Cth, suntSXWHUQLF LQIOXHQ D L 3HQWUX DFHODúL WLS GH HOHPHQW UH]LVWLY FUHúWHUHD SXWHULLQRPLQDOH VH IDFH SULQ FUHúWHUHD GLPHQVLXQLORU VXSRUWXOXL GLHOHFWULF FHHD FHFRQGXFHvQILQDOODFUHúWHUHDVXSUDIH HLGHFRQYHF LHGHFLDSXWHULLQRPLQDOH3NúLFHORUODO LSDUDPHWULWHUPLFL&DSDFLWDWHDSDUD]LWHVWHGHDVHPHQHDSURSRU LRQDOFXSHUPLWLYLWDWHDGLHOHFWULFDVXSRUWXOXLGLHOHFWULFGHSLQ]kQGúLGHGLPHQVLXQL

Zona de contactare UHDOL]HD] FRQWDFWDUHD WHUPLQDOHORU OD HOHPHQWXOUH]LVWLY 6H XWLOL]HD] PDWHULDOH FRQGXFWRDUH VSHFLILFH FRQWDFWULL vQ HOHFWURQLF7UHEXLHVSUH]LQWHRUH]LVWHQ HOHFWULFúLRWHQVLXQHWHUPRHOHFWURPRWRDUHFkWPDLPLF/DUH]LVWRDUHOHERELQDWHFRQWDFWDUHDVHIDFHSULQVWUkQJHUHDVHUWL]DUHDXQXLFSFHO GH QLFKHO VWDQDW VDX DXULW SHQWUX UH]LVWRDUH GH vQDOW ILDELOLWDWH ODHOHPHQWXOUH]LVWLY/DUH]LVWRDUHOHSHOLFXODUHVHGHSXQHRSHOLFXOFRQGXFWLYFDUHUHDOL]HD]FRQWDFWDUHDODHOHPHQWXO UH]LVWLYúLSUHJWHúWHFRQWDFWDUHD WHUPLQDOXOXL&XDOLDMGHOLSLW6Q3EVHFRQHFWHD]WHUPLQDOXOODDFHDVWSHOLFXO

Zona de contactare produce o tensLXQH WHUPRHOHFWULF QHGRULW OD ERUQHOHUH]LVWRUXOXLúLSRDWHGXFHODFUHúWHUHDFDSDFLW LLSDUD]LWH

Terminalul este necesar pentru conectarea componentelor la structura deLQWHUFRQHFWDUH 6H GLVWLQJ GRX WLSXUL LPSRUWDQWH GH WHUPLQDOH 7HUPLQDOH SHQWUXSODQWDUHLQVHU LHSHFDUHOHSXWHPQXPLúL³FODVLFH´IRUPDWHGLQFRQGXFWRDUHGHFXSUXGXEOXVWDQDWHFXGLDPHWUXOGHPP$FHVWHDLQIOXHQ HD]vQPRGGHRVHELWLQGXFWDQ DSDUD]LWDUH]LVWRUXOXL7HUPLQDOHGHWLS60'VSHFLILFHWHKQRORJLHLSHQWUXPRQWDUHGLUHFWSHVXSUDID FDUHVXQWVXEIRUPDXQRUUHJLXQLPHWDOLFHIRUPDWHGLQPDLPXOWHVWUDWXULPHWDOLFHH[HPSOX±XQVWUDWGH$J3GúLXQ VWUDW GH DOLDM GH OLSLW 6Q3E $FHVW WLS GH WHUPLQDO LQIOXHQ HD] FDSDFLWDWHDSDUD]LWDUH]LVWRUXOXL

(OHPHQWXO GH SURWHF LH DUH UROXO GH D SURWHMD HOHFWULF vQOWXUDUHDHYHQWXDOHORU VFXUWFLUFXLWH OD DWLQJHUHD FRPSRQHQWHORU PHFDQLF vQ HSWXUL]JkULHWXUL úL FOLPDWLF vQ VSHFLDO vPSRWULYD SUDIXOXL úL XPLGLW LL 6H XWLOL]HD]PDWHULDOH L]RODQWH FDUH WUHEXLH V DLE DFHOHDúL FDUDFWHULVWLFL JHQHUDOH FD FHOHutilizate la realizarea suportului dielectric.

Rezistoarele peliculare sunt în general protejate cu lacuri electroizolante sauUúLQL WHUPRULJLGH 0DL UDU VH XWLOL]HD] FDSVXOH GH SODVWLF FDSVXOH VSHFLILFHFLUFXLWHORULQWHJUDWHúLFKLDUFDSVXOHPHWDOLFH&HOHERELQDWHVXQWDFRSHULWHFXXQciment siliconic sau introduse în corp ceramic. Principalii parametrii aiUH]LVWRDUHORU VXQW QHJOLMDELO LQIOXHQ D L GH HOHPHQWXO GH SURWHF LH ([FHS LD R


15

FRQVWLWXLHFRUSXOFHUDPLFVDXPHWDOLFFDUHHVWHXWLOL]DWúLvQVFRSXOFUHúWHULLSXWHULLnominale, (a parametrilor termici în general).2EVHUYD LH ÌQ DFHVW SDUDJUDI DX IRVW SUH]HQWDWH SH VFXUW SULQFLSDOHOH FHULQ H DOHSU LORUFRQVWLWXHQWHDOHUH]LVWRUXOXL6WUXFWXUDFRQVWUXFWLYDSHQWUXGLIHULWHWLSXULGHUH]LVWRDUHYDILSUH]HQWDWvQSDUDJUDIXO

2.1.4 Dimensionarea elementului rezistiv

6H YRU SUH]HQWD vQ DFHVW SDUDJUDI FkWHYD UHOD LL FH SRW IL XWLOL]DWH SHQWUXGHWHUPLQDUHDUH]LVWHQ HLSHQWUXGLIHULWHWLSXULGHUH]LVWRDUH

2.1.4.1 Rezistoare bobinate

8QUH]LVWRUERELQDW VHRE LQHSULQERELQDUHD vQWUXQVWUDW DXQXLFRQGXFWRUQHL]RODW FX UH]LVWLYLWDWH ULGLFDW SH XQ VXSRUW GLHOHFWULF GH IRUP FLOLQGULF GLQFHUDPLFVDXILEUGHVWLFOYH]LILJXUD

Fig. 2.6 Tronsonul rezistiv al rezistorului bobinat.

6HIDFXUPWRDUHOHQRWD LLp, pasul de bobinare;La OXQJLPHDDFWLYDHOHPHQWXOXLUH]LVWLYERELQDMXO UHDOL]DWDUHR OXQJLPH

mai mare decât La ILLQG SDU LDO VFXUFLUFXLWDW OD FDSHWH GH FSFHOHOH PHWDOLFHutilizate pentru contactarea terminalelor;

D, diametrul suportului izolant;d, diametrul conductorului de bobinare.ρ, rezistivitatea materialului conductorului de bobinare.Conductorul fiind neizolat, ERELQDUHD VH IDFH DVWIHO vQFkW VSLUHOH V QX VH

DWLQJ GHFL SDVXO GH ERELQDUH S YD WUHEXL V ILH PDL PDUH GHFkW GLDPHWUXOFRQGXFWRUXOXLG&XFkWSDVXOSHVWHPDLPLFFXDWkW UH]LVWHQ DXQHL ³ERELQH´GHDFHHDúL OXQJLPH YD IL PDL PDUH 0ULPHD SDVXOXL GHSLQGH GH SUHFL]LDechipamentului utilizat pentru bobinare.

3HQWUXGHWHUPLQDUHDUH]LVWHQ HLSRUQLPGHODUHOD LDJHQHUDO

Cap. 2 Rezistoare

16

S

LR ρ= (2.1)

unde: ρ este rezistivitatea materialului; L este lungimea conductorului; S esteVHF LXQHD

În ca]XO GH ID OXQJLPHD / HVWH OXQJLPHD FRQGXFWRUXOXL ERELQDMXOXL FXlungime La. 6HSRWIDFHDSUR[LPULOH

DpDd π<<<< , (2.2)ÌQDFHVWFD]OXQJLPHDFRQGXFWRUXOXL/SRDWHILDSUR[LPDWFX

L= ns Ls (2.3)nsHVWHQXPUXOGHVSLUHDOERELQDMXOXL/s este lungimea unei spire.

5H]XOW

Dp

LL a π= (2.4)

ÌQORFXLQGvQVHRE LQH

pS

DLR aπρ= (2.5)

5H]LVWHQ D XQXL UH]LVWRU ERELQDW GHSLQGH GH WLSXO PDWHULDOXOXL DYkQG vQYHGHUH UH]LVWLYLWDWHD GH VHF LXQHD FRQGXFWRUXOXL GH SDVXO GH ERELQDUH GHGLDPHWUXO VXSRUWXOXL L]RODQW úL GH OXQJLPHD DFWLY D ERELQDMXOXL ÌQ IXQF LH GHDFHVWHPULPLVHSRWRE LQHGLIHULWHYDORULSHQWUXUH]LVWHQ

)LHFDUHPULPHGHFDUHGHSLQGHUH]LVWHQ DSUH]LQWRWROHUDQ mai mare sauPDLPLF5H]XOWvQDFHVWFD]WROHUDQ DUH]LVWHQ HLWR,

( )spLaDR thththththt 54321 ++++±= ρ (2.6)

11 ==∂∂=

ps

DL

DL

psR

Rh a

a

ππρ

ρ(2.7)

1hh 32 == (2.8)

( )1

12

2

4 −=−=∂∂=

ps

DL

DL

sp

p

R

R

ph a

a

πρπρ

(2.9)

1hh 45 −== (2.10)RezulW

( )spLDR tttttt ++++±= ρ (2.11)

LDU FHOH FLQFL PULPL GH FDUH GHSLQGH UH]LVWHQ D DX DFHHDúL SRQGHUH ODWROHUDQ ÌQSUDFWLFGHFLVLYHVWHYDULD LDUH]LVWLYLW LL

&RHILFLHQWXOGHYDULD LHFXWHPSHUDWXUDDOUH]LVWHQ HLYDIL

spLDR αααααα ρ −−++= (2.12)


17

$YkQGvQYHGHUHDFHDVWFRPSHQVDUHDFRHILFLHQ LORUGHGLODWDUHvQSUDFWLFVHSRDWHFRQVLGHUDF

ραα ≅R (2.13)

DHFL YDULD LD UH]LVWHQ HL FX WHPSHUDWXUD HVWH SXWHUQLF GHSHQGHQW GH WLSXOmaterialului elementului rezistiv.

2.1.4.2 Rezistoare peliculare cilindrice

)RUPDFRQVWUXFWLYDUH]LVWRDUHORUSHOLFXODUHHVWHvQJHQHUDOGHWHUPLQDWGHforma suportului dielectric. Din acest punct de vedere ele pot fi cilindrice sauSDUDOHOLSLSHGLFH)DFH[FHS LH UH]LVWRDUHOH SURWHMDWH FX FDSVXOHPHWDOLFH SODVWLFH'DU úL vQ DFHVW FD] WURQVRQXO UH]LVWLY DQVDPEOXO HOHPHQW UH]LVWLY úL VXSRUWdielectric este identic. Deci vom considera un rezistor pelicular cu tronsonul deIRUP FLOLQGULF $FHDVW VROX LH FRQVWUXFWLY HVWH XWLOL]DW OD R PDUH SDUWH GLQUH]LVWRDUHOH SHOLFXODUH FX FDUERQ FX SHOLFXO PHWDOLF FX SHOLFXO GLQ R[L]LPHWDOLFLFXJOD]XUPHWDOLF ,QGLIHUHQWGHPRGXO WHKQRORJLFSLUROL]HYDSRUDUHvQ YLG KLGUROL] HOHFWUROL] SXOYHUL]DUH SULQ FDUH VH RE LQH SHOLFXOD UH]LVWLY

HOHPHQWXO UH]LVWLY GLPHQVLRQDUHD UH]LVWHQ HL HVWH LGHQWLF DYkQG vQ YHGHUH FSULQFLSLXOGH UHDOL]DUH HVWH DFHODúL6XSRUWXOGLHOHFWULF HVWH FLOLQGULF ILLQG UHDOL]DWGLQFHUDPLF

/DDFHVWHUH]LVWRDUHVHGHSXQHLQL LDORSHOLFXOUH]LVWLYSHWRDWID DODWHUDOa suportului dielectric, vezi figura 2.7.

2EVHUYD LH. Înainte de depunerea peliculei rezistive, se depun la capeteleVXSRUWXOXL GLHOHFWULF SHOLFXOH FRQGXFWLYH QHFHVDUH SHQWUX UHDOL]DUHD FRQWDFWULLWHUPLQDOHORU3HOLFXODUH]LVWLYYDILGHSXVGHIDSWSHRVXSUDID ODWHUDOSDU LDODVXSRUWXOXLGLHOHFWULFILLQGSDU LDOVXSUDSXVSHVWHSHOLFXODFRQGXFWLYILJXUD

D

La

3HOLFXOFRQGXFWLY

3HOLFXOFRQGXFWLYSHOLFXOUH]LVWLY

3HOLFXOUH]LVWLY

Fig. 2.7 Tronson rezistiv pentru rezistoare peliculare cilindrice.

6HXWLOL]HD]QRWD LLOHD, diametrul suportului dielectric;LaOXQJLPHDDFWLYDSHOLFXOHLUH]LVWLYHg, grosimea peliculei rezistive.

Cap. 2 Rezistoare

18

5H]LVWHQ D DFHVWHL SHOLFXOH WXEXODUH VH FRQVLGHU FD ILLQG R UH]LVWHQ GHRULJLQH úLRYRPQRWD FX50. Grosimea g a peliculei se poate considera ca fiindFRQVWDQWSHQWUXXQDQXPLWWLSGHUH]LVWRUÌQSUDFWLFJGHSLQGHvQSULPXOUkQGGHSURFHVXO WHKQRORJLF IRORVLW SHQWUX GHSXQHUHD SHOLFXOHL GDU vQ FDGUXO DFHOXLDúLSURFHVHDVHSRDWHPRGLILFD vQPRGFRQWURODWúL vQ IXQF LHGHYDORDUHDUH]LVWHQ HLvQWUR DQXPLW SODM 'HFL vQ FDOFXOH J SRDWH IL FRQVLGHUDW FD ILLQG FRQVWDQWHURDUHD ILLQG UHODWLYPLF úL DFHDVWDGHSLQGHGHSUHOXFUDUHD VXSUDIH HL VXSRUWXOXLGLHOHFWULF úL SUHFL]LD HFKLSDPHQWHORU XWLOL]DWH SHQWUX GHSXQHUH )RORVLQG UHOD LDSHQWUXFDOFXOXOUH]LVWHQ HLúLDYkQGvQYHGHUHF

g<<D (2.14)VHSRDWHDSUR[LPDF

.0 D

L

gDg

LR aa

πρ

πρ == (2.15)

Raportul,

gs

ρρ = (2.16)

SRDUWQXPHOHGHUH]LVWLYLWDWHVXSHUILFLDOúLHVWHRFDUDFWHULVWLFSHQWUXRULFH WLSGHSHOLFXOUH]LVWLYUHSUH]HQWkQGUH]LVWHQ DXQXLSWUDW6HPVRDU vQΩ/ úLVHFLWHúWHRKPLSHXQLWDWHDGHVXSUDID VDXSHSWUDWRaportul,

D

LK a

f π= (2.17)

VH QXPHúWH IDFWRU GH IRUP VDX DVSHFW úL UHSUH]LQW QXPUXO SWUDWHORU FX ODWXUDHJDO FX O LPHD SHOLFXOHL UH]LVWLYH FRQ LQXWH GH HOHPHQWXO UH]LVWLY / LPHDUHSUH]LQWGLPHQVLXQHDSHUSHQGLFXODUHLSHGLUHF LDGHFXUJHUHDFXUHQWXOXL5H]XOWRUHOD LHJHQHUDOSHQWUXUH]LVWRDUHOHSHOLFXODUH

fsKR ρ= (2.18)

8UPHD] RSHUD LD GH VSLUDOL]DUH DMXVWDUH D SHOLFXOHL UH]LVWLYH RE LQXWHDQWHULRUFDUHDUHRIRUPSUDFWLFWXEXODU$FHDVWRSHUD LHHVWHQHFHVDUGLQGRX

PRWLYHHVHQ LDOH• 9DORULOH PD[LPH DOH UH]LVWHQ HORU RE LQXWH SULQ GHSXQHUHD H[SXV SHOLFXO

WXEXODUVXQWUHODWLYVF]XWHILLQGvQJHQHUDOGHRUGLQXO.Ω(1kΩ-10kΩ). DeciHUD QHFHVDU R PHWRG SHQWUX FUHúWHUHD YDORULL UH]LVWHQ HL DVWIHO vQFkW V VHDMXQJODFHOSX LQ0Ω-10MΩLQWHUYDOX]XDOvQHOHFWURQLF

• 3HGHDOWSDUWHGDFSHQWUXILHFDUHYDORDUHQRPLQDODUH]LVWHQ HLVDUILXWLOL]DWQXPDL DFHVW SURFHGHX FRVWXO XQXL UH]LVWRU DU IL IRDUWH ULGLFDW GDWRULWFRPSOH[LW LL SURFHGHXOXL WHKQRORJLF ùL vQ DFHVW FD] RSHUD LD GH VSLUDOL]DUHQXPLWúLGHDMXVWDUHHVWHIRDUWHHILFLHQWSHQWUXFSRUQLQGGHODRGHSXQHUHLQL LDOSHQWUXRDQXPLWYDORDUH50VHSRWRE LQHYDORULQRPLQDOHGH«RULPDLPDUL2SHUD LDGHDMXVWDUHILLQGPXOWPDLLHIWLQGHFkWFHDGHGHSXQHUHDpeliculei rezistive, indiferent de tipul acesteia.


19

6SLUDOL]DUHD DUH úL R VHULH GH GH]DYDQWDMH úL WUHEXLH UHDOL]DW DYkQG vQ YHGHUHDQXPLWHFRQGL LL3ULQFLSDOXOGH]DYDQWDMHOHFWULFDOVSLUDOL]ULLvOFRQVWLWXLHFUHúWHUHDLQGXFWDQ HL SDUD]LWH D HOHPHQWXOXL UH]LVWLY úL HYLGHQW D UH]LVWRUXOXL 'H DFHHDSHQWUXDQXPLWH WLSXULGH UH]LVWRDUHFHSRW IL XWLOL]DWH OD vQDOW IUHFYHQ QXPUXOVSLUDOL]ULORUHVWHUHGXVODFHOPXOW

6SLUDODUHDVHUHDOL]HD]FXGLVFXULDEUD]LYHVDXFXODVHUÌQWLPSXOVSLUDOULLYDORDUHD HVWH FRQWURODW 'XS VSLUDODUH HOHPHQWXO UH]LVWLY FDSW IRUPD XQHLpelicule elicoidale, figura 2.8.

Fig. 2.8 Tronson rezistiv spiralat.6HQRWHD]p, pasul de spiralare;DO LPHDúDQ XOXLEO LPHDSHOLFXOHLUH]LVWLYHVSLUDODWH

RezistHQ D5YDIL

fsKR ρ= (2.19)

pb

DLK a

fπ= (2.20)

( )app

DLR a

s −=

πρ (2.21)

sau

gbp

DLR aρπ

= (2.22)

'HFLvQDFHVWFD]UH]LVWHQ DGHSLQGHGHWLSXOPDWHULDOXOXLSHOLFXODUDYkQGvQYHGHUH UH]LVWLYLWDWHD GH GLDPHWUXO VXSRUWXOXL GLHOHFWULF OXQJLPHD DFWLY DHOHPHQWXOXLUH]LVWLYúLGLPHQVLXQLOHGHVSLUDODUHSDE

Raportul R/R0VHQXPHúWHUDSRUWGHVSLUDOL]DUH

( )( )app

D

R

R

−==

2

0

πβ (2.23)

ÌQSUDFWLFβ ia valori de 2 la 2000.FileWDUHDHOHPHQWXOXLUH]LVWLYWUHEXLHVvQGHSOLQHDVFFRQGL LLOH

Cap. 2 Rezistoare

20

- ILOHWXOWUHEXLHVvQFHDSID GHSHOLFXODFRQGXFWLYODRGLVWDQ GHFHOSX LQb;

- SDVXO ILOHWXOXL WUHEXLH V ILH GH FHO SX LQ RUL PDL PDUH GHFkW O LPHDúDQ XOXL

- OXQJLPHD ]RQHL ILOHWDWH V ILH FHOSX LQGLQ OXQJLPHD WRWDO D VXSRUWXOXLdielectric;

- SLHUGHULOH GH VXSUDID SULQ VSLUDOL]DUH V QX GHSúHDVF SHQWUX D QXGLPLQXDH[FHVLYSXWHUHDQRPLQDO

'LPHQVLXQLOHSDEGHSLQGGHPRGXOGHUHDOL]DUHDOILOHWULL'LVFXULOHDEUD]LYHDXo grosime de 0,2…0,5mm, iar pasul ia valori de la 0,5mm la 3mm. În cazullaserului pasul de filetare ia valori de la 0,3mm la 1,5mm.

8WLOL]kQGUHOD LDVHSRDWHGHWHUPLQDWROHUDQ DUH]LVWHQ HLWR

( )pbgLDR ththththththt 654321 +++++±= ρ (2.24)

11 ==∂∂=

gbp

DL

DL

gbpR

Rh a

a

ππρ

ρ(2.25)

1hh 32 == (2.26)

( )1

12

2

4 −=−=∂∂=

gbp

DL

DL

bpg

g

R

R

gh a

a

πρπρ

(2.27)

1hh 65 −== (2.28)5H]XOWWROHUDQ DWR,

)( pbgLDR ttttttt +++++±= ρ (2.29)

'HFLWRDWHPULPLOHGHFDUHGHSLQGHWROHUDQ DDXDFHHDúLSRQGHUHODWROHUDQ DUH]LVWHQ HL&DúLvQFD]XODQWHULRULPSRUWDQWHVWHYDULD LDUH]LVWLYLW LL

&RHILFLHQWXOGHYDULD LHFXWHPSHUDWXUDDOUH]LVWHQ HLαR, va fi,

bbgLDR ααααααα ρ −−−++= (2.30)

$YkQG vQ YHGHUH YDORDUHD UHODWLY PLF D FRHILFLHQ LORU GH GLODWDUH SUHFXP úLFRPSHQVDUHDWHUPLFFRQIRUPUHOD LHLvQSUDFWLFvQJHQHUDO

αR≅ αρ (2.31)

2.1.4.3 Rezistoare peliculare paralelipipedice

6XSRUWXOGLHOHFWULFHVWHUHDOL]DWVXEIRUPSDUDOHOLSLSHGLF$YkQGvQYHGHUHFSHGHRSDUWHJURVLPHD vQO LPHDSDUDOHOLSLSHGXOXLHVWHPXOWPDLPLF GHFkWFHOHODOWH GLPHQVLXQL LDU SH GH DOW SDUWH SHOLFXOD UH]LVWLY HVWH SODQ DFHVWHUH]LVWRDUHPDLVXQWQXPLWHúL³SODQH´6HYRUSUH]HQWDvQFRQWLQXDUHUH]LVWRDUHOHFXstraturi groase.

3HOLFXOD UH]LVWLY VH UHDOL]HD] SULQ PHWRGD VHULJUDILF PHWRG VSHFLILFWHKQRORJLHLFXVWUDWXULJURDVH76*GHXQGHúLGHQXPLUHDGHUH]LVWRDUHFXSHOLFXOHgroase.


21

&D PDWHULDO VH XWLOL]HD] R SDVW UH]LVWLY 3HQWUX YDOori uzuale aleUH]LVWHQ HL SkQ OD «0Ω VH IRORVHúWH XQ DPHVWHF IRUPDW GLQ SXOEHUHPHWDOLF VDX R[L]LPHWDOLFL FX OLDQ L úL VROYHQ L RUJDQLFL 3HQWUX YDORULPDUL DOHUH]LVWHQ HL VHXWLOL]HD] FHUPHWXULOH IRUPDWHGLQDPHVWHFXOXQHLSXOEHULPHWDOLFHFXSXOEHUHGLHOHFWULFOLDQ LúLVROYHQ L'HDFHHDDFHVWHUH]LVWRDUHPDLVXQWQXPLWHúLFRPSR]LWH

3ULQFLSLXO VHULJUDILF IRORVLW PXOW vQ HOHFWURQLF DWkW OD UHDOL]DUHDFRPSRQHQWHORU SDVLYH GDU úL SHQWUX FDEODMH LPSULPDWH FLUFXLWH KLEULGH VHQ]RULHOHFWULFLHWFXWLOL]HD]RVLWVHULJUDILFQXPLWúLHFUDQFDUHDUHODED]RVLWFXRFKLXULIRDUWHILQHUHDOL]DWGLQR HOSODVWLFFDUHVHDFRSHUSULQWUXQSURFHGHXIRWRJUDILFFXLPDJLQHDQHJDWLY3ULQLPSULPDUHVHRE LQHLPDJLQHDSR]LWLY'HFLvQ FD]XO QRVWUX GXS UHDOL]DUHD VLWHL VHULJUDILFH DFHDVWD VH VXSUDSXQH SHVWHVXSRUWXOGLHOHFWULFúLFXDMXWRUXOXQHLUDFOHWHSDVWDUH]LVWLYHVWHWUHFXWSHVWHVLWLPSULPkQGXVHvQDFHVWIHOSHVXSRUWIRUPDSHOLFXOHORUSHFDUHOHGRULPDOHRE LQH

2 SDVW UH]LVWLY UHVSHFWLY SHOLFXOD UH]LVWLY HVWH FDUDFWHUL]DW GH GRLSDUDPHWULLHVHQ LDOL- ρsUH]LVWLYLWDWHDVXSHUILFLDOGHILQLWDQWHULRU- ps, [W/mm2@SXWHUHDVSHFLILFUHSUH]HQWkQGSXWHUHDFHSRDWHILHYDFXDWFWUH

PHGLXODPELDQWGHXQSWUDWXQLWDWHDGHVXSUDID IXQF LRQkQGvQWUXQPHGLXDPELDQW FX WHPSHUDWXUD HJDO FX FHD QRPLQDO GHFL Ss UHSUH]LQW GH IDSWSXWHUHDQRPLQDODXQHLSHOLFXOHUH]LVWLYHSWUDWH3HOLFXOHOH JURDVH SRW DYHD GLYHUVH IRUPH JHRPHWULFH vQV vQ FD]XO

UH]LVWRDUHORU UHDOL]DWH vQ VHULH VH XWLOL]HD] SUHSRQGHUHQW GRX IRUPHGUHSWXQJKLXODUúLSOULH

)RUPDGUHSWXQJKLXODUHVWHFRQIRUPILJXULL 2 2 1 34 3

l

L

A

A′ 1

4

sec LXQHDAA ′Fig. 2.97URQVRQUH]LVWLYFXSHOLFXOJURDVGUHSWXQJKLXODU

VSHFLILFUH]LVWRDUHORU60' VXSRUW GLHOHFWULF GLQ DOXPLQ SHOLFXO FRQGXFWLY GLQ $J3G SHOLFXO UH]LVWLY VXSUDSXV

SHVWH FHD FRQGXFWLY SHOLFXO UH]LVWLY DFWLY FHD FDUH GHWHUPLQ UH]LVWHQ D

/DED]DGLPHQVLRQULLVWDXUHOD LLOH

l

LKR sfs ρρ == (2.32)

Cap. 2 Rezistoare

22

LlpP s= (2.33)XQGH3HVWHSXWHUHDGLVLSDWHYDFXDWGHUH]LVWRU

'LQUHOD LLOHUH]XOW

Rp

Pl

s

sρ= (2.34)

lR

Lsρ

= (2.35)

sau,

ssp

PRL

ρ= (2.36)

R

Ll sρ= (2.37)

3HQWUX IRUPD GUHSWXQJKLXODU IDFWRUXO GH DVSHFW .f=L/l, ia valori înLQWHUYDOXO«SXWkQGILPDLPLFVDXPDLPDUHGHFkW5HOD LLOHVHXWLOL]HD]SHQWUX.fúLUHOD LLOHSHQWUX.f > 1.

8UPHD] úL OD DFHVW WLS GH UH]LVWRU RSHUD LD GH DMXVWDUH D UH]LVWHQ HL FDUHFRQVWvQvQOWXUDUHDSDU LDODXQHLSHOLFXOH$MXVWDUHDVHIDFHFXSUDIDEUD]LYVDXFX ODVHU ILLQG FRQWURODW vQ WLPSXO DMXVWULL FkQG YDORDUHD UH]LVWHQ HL DMXQJH ODYDORDUHDGRULWDMXVWDUHDHVWHRSULW'XSDMXVWDUHSHOLFXODUH]LVWLYDUHIRUPDGLQfigura 2.10.

laj

L

lhaj

Fig. 2.103HOLFXOUH]LVWLYDMXVWDW

8WLOL]kQG DMXVWDUHD PULPLOH FH LQWHUYLQ vQ UHOD LLOH GH GLPHQVLRQDUH VHPRGLILF

2SHUD LDGHDMXVWDUHHVWHXWLOL]DWSHQWUXF- GXSGHSXQHUHDVHULJUDILFQXVHSRW RE LQH WROHUDQ HPLFL WROHUDQ DHVWHGH

±10…±30%.- SURFHGHXOVHULJUDILFHVWHUHODWLYVFXPSGDFSHQWUXILHFDUHYDORDUHQRPLQDOVH

XWLOL]HD]QXPDLGHSXQHUHD VHULJUDILFSUH XO UH]LVWRUXOXL DU IL UHODWLY ULGLFDWSULQRSHUD LD GH DMXVWDUH SRUQLQG GH OD R SHOLFXO GUHSWXQJKLXODU GHSXV VHRE LQPDLPXOWHYDORULQRPLQDOHUHGXFkQGXVHSUH XO


23

Pentru un factor de aspect Kf!VHDGRSWIRUPDGLQILJXUDXQGHHVWHSUH]HQWDWQXPDLSHOLFXODDFWLYIUFHDGHFRQWDFWDUHFDUHHVWHDVHPQWRDUHFXFHDGHODIRUPDGUHSWXQJKLXODU

L

h

L1 L2 L1

l

lll

l

laj

L1 L1L2

L

h

a) înainte de ajustare EGXSDMXVWDUHIRUPDLGHDOFig. 2.113HOLFXOUH]LVWLYVXEIRUPGHSOULH

3ULQPHWRGDVHULJUDILFVHGHSXQHRSHOLFXOUH]LVWLYFDFHDGLQILJXUDDFXGLPHQVLXQLOHFRQIRUPILJXULL'XSDMXVWDUHFDUHHVWHREOLJDWRULHvQDFHVWFD]LGHDOL]kQGVHRE LQHRIRUPFDFHDGLQILJXUDE

Pentru GHWHUPLQDUHD GLPHQVLXQLORU GRULQG V RE LQHP XQ UH]LVWRU FXUH]LVWHQ D QRPLQDO 5N úL SXWHUHD QRPLQDO 3N XWLOL]kQG R SDVW FX SDUDPHWULLFXQRVFX Lρs, ps, TN, TMVHSURFHGHD]vQIHOXOXUPWRU

6HSRUQHúWHGHODRUH]LVWHQ GHRULJLQH50,R0=(0,7…0,8) RN (2.38)

6HGHWHUPLQO LPHDO

mmRp

Pl

s

sN 75,00

≥= ρ(2.39)

'DF O HVWHPDLPLF GHFkW PP VH YD OXD O PP VDX VH DOHJH DOWSDVW

3HQWUX FDOFXOXO UH]LVWHQ HL VH DUH vQ YHGHUH F SWUDWHOH GH OD FRO XUL FHOHvQHJULWH vQ ILJXUD E GDWRULW FLUFXOD LHL FXUHQWXOXL DX R UH]LVWHQ UHGXV ODMXPWDWH

ssaj

ssl

lh

l

l

l

LR ρρρρ −+++= 22

2 10 (2.40)

l

hlLR aj

s

22 10 ++=

ρ(2.41)

llL aj 22 += (2.42a)

ajllLLLL ++=+= 222 121 (2.42b)

Cap. 2 Rezistoare

24

(VWH GH UHPDUFDW F VROX LD QX HVWH XQLF GHRDUHFH /2 sau laj se aleg. OYDORDUH X]XDO HVWH Oaj O 6D SUHVXSXV GH DVHPHQHD F UH]LVWRUXO DUH DFHHDúLWHPSHUDWXUQRPLQDOFXFHDDSDVWHLUH]LVWLYH

Sintetizând, pentru proiectarea rezistoarelor cu straturi groase se va utilizaDOJRULWPXOXUPWRU

&HULQ HOHGHSURLHFWDUHVVHSURLHFWH]HXQUH]LVWRUFXYDORDUHDQRPLQDODUH]LVWHQ HL5NúLSXWHUHDQRPLQDO3N.

$OHJHUHD WLSXOXL GH SDVW 'H RELFHL SURGXFWRULL GH SDVWH UH]LVWLYHUHDOL]HD]SDVWHFXUH]LVWHQ DVXSHUILFLDOHJDOFXXQLWDWHDSHQWUXILHFDUHGHFDG(10Ω/ , 100Ω/ , 1kΩ/ , 10KΩ/ HWF ÌQ IXQF LHGH5N úL3N se alege tipul deSDVWDVWIHOFD5N≅(0.5…20)ρsúL3N≅(4…15)ps.

6HFDOFXOHD]IDFWRUXOGHDVSHFW

s

Nf

R

l

LK

ρ== (2.43)

Pentru Kf∈>@ VH DOHJH IRUPD GUHSWXQJKLXODU LDU SHQWUX .f=6…20,IRUPDSOULH)RUPDGUHSWXQJKLXODUSRDWHILFXVDXIUDMXVWDUH

D )U DMXVWDUH DFHDVW YDULDQW HVWH XWLOL]DW vQ JHQHUDO OD FLUFXLWHOHhibride.

ÌQ DFHVW FD] GDF /O VH XWLOL]HD] UHOD LLOH vQ FDUH VHvQORFXLHúWH5FX5N úL3FX3NúLFRQGL LDFD/≥PP'DF/PPVHYDalege L=0,75mm din motive tehnologice.

'DF≤L/l≤VHXWLOL]HD]UHOD LLOHvQFDUHVHvQORFXLHúWH5cu RN úL3FX3NúLFRQGL LDFDO≥PP'DFGLQFDOFXOHUH]XOWOPPVHva alege l=0,75mm din motive tehnologice.

b) Cu ajustare$YkQGvQYHGHUHDEDWHUHDUH]LVWHQ HLUH]XOWDQWHGXSGHSXQHUHDVHULJUDILFúL

IDSWXO F SULQ DMXVWDUH YDORDUHD UH]LVWHQ HL FUHúWH VH YD XWLOL]D vQ FDOFXOH RUH]LVWHQ ]LVGHRULJLQH50,

R0=(0,7…0,8) RN (2.44)3ULQ DMXVWDUH VH UHGXFH O LPHD SHOLFXOHL SH R SRU LXQH GHFL úL SXWHUHD

HYDFXDWGHDFHVWD3HQWUXDQXVXSUDVROLFLWDWHUPLFDFHDVWSRU LXQHHVWHQHFHVDURUHGXFHUHDSXWHULLVSHFLILFHFHWUHEXLHOXDWvQFDOFXOHODRDQXPLWYDORDUHS¶s,

( )ajs

s

llL

Ll

p

p

−=

'(2.45)

5H]XOW

saj

s pl

llp

−=' (2.46)

ÌQSUDFWLFOajOúLVHSRDWHOXDvQFDOFXOHS’s= 0,5ps.

Pentru 0,5<KfVHGHWHUPLQPDLvQWkLGLPHQVLXQHD/


25

mmp

RPL

ss

N 75,02 0 ≥=

ρ(2.47)

'DF/PPVHYDDOHJH/ PP

0R

Ll sρ= (2.48)

Pentru 1≤Kf≤VHGHWHUPLQPDLvQWkLO

mmRp

Pl

s

sN 75,02

0≥= ρ

(2.49)

'DFOPPVHYDDOHJHO PP

lR

Lsρ0= (2.50)

'DF≤ K f ≤VHDGRSWIRUPDSOULHDFUHLGLPHQVLRQDUHVHUHDOL]HD]XWLOL]kQGUHOD LLOH

2EVHUYD LL- În toate cazurile de proiectare a rezistoarelor cu pelicule groase s-a presupusF UH]LVWRUXO DUH DFHHDúL WHPSHUDWXU QRPLQDO FD úL SDVWD UH]LVWLY XWLOL]DW$FHVWDILLQGFD]XOFHOPDLLQGLFDW'DF WRWXúLVHGRUHúWHRWHPSHUDWXUQRPLQDOθNR D UH]LVWRUXOXLGLIHULWGHFHDDSDVWHLθNP vQ WRDWH UHOD LLOH vQ ORFGHSs, se vaXWLOL]DRSXWHUHVSHFLILFPRGLILFDWS’’

s,

NPM

NRMss pp

θθθθ

−−

='' (2.51)

- ÌQIXQF LHGHGLPHQVLXQLOHVXSRUWXOXLGLHOHFWULFDOUH]LVWRUXOXLvQSUDFWLFH[LVWúLDQXPLWHOLPLWULLDOHYDORULORUPD[LPHSHQWUXO/úLK

2.1.5 Zgomotul intern al rezistoarelor

Prin zgomot electric se vQ HOHJHRULFH VHPQDO HOHFWULF SDUD]LW QHGRULW FH VHSRDWHVXSUDSXQHSHVWHVHPQDOXOHOHFWULFXWLOSXUWWRUGHLQIRUPD LHÌQIXQF LHGHYDORDUHDVD]JRPRWXOPRGLILFPDLPXOWVDXPDLSX LQVHPQDOXOXWLOSXWkQG FRQGXFH vQ DQXPLWH VLWXD LL FKLDU OD IXQF LRQDUHD HURQDW D FLUFXLWHORUelectronice. =JRPRWXOXQHLFRPSRQHQWHHOHFWURQLFHVHvPSDUWHvQGRXPDULFDWHJRULL• ]JRPRW LQWHUQ GHSHQGHQW GH WLSXO FRPSRQHQWHL VWUXFWXUD úL WLSXO PDWHULDOHORU

XWLOL]DWH UHSUH]LQW ]JRPRWXO FH DSDUH OD ERUQHOH FRPSRQHQWHL vQ WLPSXOIXQF LRQULL DFHVWHLD VXUVHOH GH ]JRPRW ILLQG vQ LQWHULRUXO FRPSRQHQWHL RULFHFRPSRQHQWHOHFWURQLFSUH]LQWXQDVHPHQHD]JRPRW

• ]JRPRWH[WHUQUHSUH]HQWkQG]JRPRWXOFHSRDWHVDSDUODERUQHOHFRPSRQHQWHLvQ WLPSXO IXQF LRQULL DFHVWHLD GDWRULW XQRU VXUVH H[WHUQH GH ]JRPRW DSDUHSUHGRPLQDQWSULQUHFHS LHHOHFWULFPDJQHWLFúLHOHFWURPDJQHWLFDFkPSXOXLGLQ

Cap. 2 Rezistoare

26

YHFLQWDWH úL SULQ FXSODMH SULQ LPSHGDQ D FRPXQ HVWH SXWHUQLF GHSHQGHQW GHPHGLXO vQ FDUH IXQF LRQHD] FRPSRQHQWD úL GH PRGXO GH LQWHUFRQHFWDUH DFRPSRQHQWHORU GLVFLSOLQD FDUH VH RFXS FX VWXGLXO ]JRPRWHORU H[WHUQH SRDUWQXPHOHFRPSDWLELOLWDWHHOHFWURPDJQHWLF

ÌQDFHVWSDUDJUDIVHDQDOL]HD]]JRPRWXO LQWHUQDOUH]LVWRDUHORUFDUHSRDWHILWHUPLFúLGHFXUHQW

Zgomotul termic.

6H FRQVWDW F GDF LHúLUHD XQXL DPSOLILFDWRU H FRQHFWDW OD ERUQHOH XQXLRVFLORVFRS úL LQWUDUHD H VFXUWFLUFXLWDW SH HFUDQXO WXEXOXL YD DSDUH XQ VHPQDOGHWHULRUDWGH]JRPRWXODPSOLILFDWRUXOXL'DFODLQWUDUHVHFRQHFWHD]XQUH]LVWRUVHREVHUY R FUHúWHUH D QLYHOXOXL ]JRPRWXOXL 'HFL UH]LVWRUXO VH IDFH VLP LW úL SULQLQWHUPHGLXOXQHLWHQVLXQLGH]JRPRW([LVWHQ DWHQVLXQLLIOXFWXDQWHSHHFUDQWUHEXLHVILHUH]XOWDWXOXQRUFDX]HGLQLQWHULRUXOUH]LVWRUXOXLGDFFXUHQWXOFHWUHFHSULQUH]LVWRUúL YDORDUHD UH]LVWHQ HL DU IL FRQVWDQWH WHQVLXQHD ]JRPRWXO DU IL QXO $úD vQVFRQFKLGHP F PLFURVFRSLF H[LVW R IOXFWXD LH D PHFDQLVPHORU FH GHWHUPLQFRQGXF LD vQ UH]LVWRU &XUHQWXO H GHWHUPLQDW GH GHSODVDUHD HOHFWURQLORU 6F]kQGWHPSHUDWXUD OD . H SRVLELO FD vQ PHWDO V QX FLUFXOH QLFL XQ HOHFWURQ /D RWHPSHUDWXUPDLPDUHGH.HOHFWURQLLVHPLúFGDWRULWHQHUJLHLWHUPLFH]JRPRWXOrezultat purtând denumirea de zgomot termic. Pentru cuantificarea nivelului de]JRPRWVHXWLOL]HD]YDORDUHDPHGLHSWUDWLFGHRDUHFHYDORDUHDPHGLHSRDWHILQXODWkWGDFvQWUXQLQWHUYDOILQLWGHWLPSVDUFLQLOHVXQWvQUHSDXVFkWúLGDFVDUFLQLOHVHGHSODVHD]HJDOvQVHQVXULFRQWUDUH3XWHUHDGH]JRPRWWHUPLFHVWHGDWGHUHOD LDOXL1\TXLVW

fkT4=Pz ∆g (2.52)

LDUWHQVLXQHDSWUDWLFPHGLHGH]JRPRWYDIL

fkT4=Uz2 ∆Rg (2.53)

unde: - k este constanta lui Boltzmann KJ /10 38,1 23−⋅ ;- 7HVWHWHPSHUDWXUDDEVROXWDUH]LVWRUXOXL- ∆IHVWHLQWHUYDOXOGHIUHFYHQ EDQGDvQFDUHVHIDFHPVXUWRDUHD- 5HVWHYDORDUHDUH]LVWHQ HLExemplu: T=290 K, R=10kΩ, ∆I N+]UH]XOW8zg=1,27 µV.

6H REVHUY F DFHHDúL YDORDUH DU IL IRVW RE LQXW LQGLIHUHQW GH YDORDUHDDEVROXWDIUHFYHQ HLGHFLGDFLQWHUYDOXOGHIUHFYHQ DUILIRVW>N+]N+]@VDX[100 kHz, 110 kHz].,QWURGXFkQGQRWD LD*SHQWUXFRQGXFWDQ * 5VHSRDWHVFULHH[SUHVLDFXUHQWXOXLGH]JRPRWFHVWUEDWHUH]LVWRUXO


27

fGkT4=I2z ∆g (2.54)

6HSRDWHGDSHED]DUHOD LLORUúLXUPWRDUHDHFKLYDODUHDXQXLUH]LVWRUdin punct de vedere al zgomotului,

R

R

R

2

zgU

a)

b) 2zgI

Fig. 2.126FKHPDHFKLYDOHQWDXQXLUH]LVWRUGLQSXQFWGHYHGHUHDO]JRPRWXOXLDFXVXUVGHWHQVLXQHEFXVXUVGHFXUHQW

Zgomotul de curent (1/f).

/D DQXPLWH WLSXUL GH UH]LVWRDUH VH FRQVWDW F OD DSOLFDUHD XQHL WHQVLXQL ODborne, la trecerea unei componente de curent continuu prin rezistor zgomotulDFHVWRUD HFXXQRUGLQGHPULPHPDLPDUHGHFkW ]JRPRWXO WHUPLF$FHVW ]JRPRWGDWRUDW WUHFHULL FXUHQWXOXL SULQ UH]LVWRU SRDUW QXPHOH GH ]JRPRW GH FXUHQW úL HGDWRUDW FRQGXFWLELOLW LL IOXFWXDQWH D FRQWDFWXOXL LQWHUQ LPSHUIHFW GLQWUH ]RQHOHHOHPHQWDUHFRQGXFWRDUHDOHPDWHULDOXOXLUH]LVWLYQHRPRJHQ(VWHGHDúWHSWDWGHFLFODUH]LVWRDUHOHFXVWUXFWXUFRPSR]LWVDSDUXQ]JRPRWGHFXUHQWPDLPDUHGHFkWODFHOH FX SHOLFXO GH PHWDO 'LQ FDWHJRULD FRPSR]LWHORU IDF SDUWH úL UH]LVWRDUHOH FXJOD]XUPHWDOLFÌQIXQF LHGHFDQWLWDWHDGHPHWDOGLQSDVWYDULD]úLUH]LVWLYLWDWHDSDVWHLUH]LVWLYLWDWHDVFDGHFXFUHúWHUHDFDQWLW LLGHPHWDO3HQWUXYDORDUHDSWUDWLFPHGLHDWHQVLXQLLGH]JRPRWGHFXUHQWHVWHYDODELOUHOD LD

Rff

IK=U 202

2z ∆

kg (2.55)

unde,I0 esteFXUHQWXOFRQWLQXXSULQUH]LVWRUIHVWHIUHFYHQ DFHQWUDODEHQ]LL∆f, ∆f esteEDQGD GH IUHFYHQ vQ FDUH VH IDFH PVXUDUHD 5 HVWH YDORDUHD UH]LVWHQ HL . RFRQVWDQW

Cap. 2 Rezistoare

28

&RQVWDQWD. VH GHWHUPLQ H[SHULPHQWDO úL GHSLQGH SXWHUQLF GH FRPSR]L LDSHOLFXOHLUH]LVWLYHGHUDSRUWXOGLQWUHSDUWLFXOHOHFRQGXFWRDUHúLFHOHQHFRQGXFWRDUH

La conectarea în serie sau în paralel a rezistoarelor, zgomotul rezistoruluiHFKLYDOHQW FUHúWH vQVXPkQGXVH 6H FRQVLGHU GRX UH]LVWRDUH FX YDORULOH

UH]LVWHQ HORU 51, respectiv R2 úL WHQVLXQLOH SWUDWLFH PHGLL GH ]JRPRW 2

1zgU ,

respectiv 2

2zgU FHVHFRQHFWHD]vQVHULH5H]XOWVFKHPDHFKLYDOHQWGLQSXQFWGH

vedere al zgomotului din figura 2.13

∼ ∼ ∼ R1 2

1zgU 2zgsU

R2 2

2zgU RS

Fig. 2.136FKHPDHFKLYDOHQWGLQSXQFWGHYHGHUHDO]JRPRWXOXLODFRQHFWDUHDVHULH

7HQVLXQLOHGH]JRPRWILLQGLQGHSHQGHQWHUH]XOW

RS= R1+R2, 22

21

2zgzgzgs UUU += (2.56)

3HQWUXQUH]LVWRDUHFRQHFWDWHvQVHULHWHQVLXQHDSWUDWLFPHGLHGH]JRPRWDrezistorului echivalent va fi

∑=

=n

izgizgs uu

1

22 (2.57)

/D FRQHFWDUHD vQ SDUDOHO D FHORU GRX UH]LVWRDUH FH SUH]LQW FXUHQ LL GH

zgomot 21zgi , respectiv 2 2zgi UH]XOWVFKHPDHFKLYDOHQWGLQILJXUD

≡R1 R2 Rp 2

1zgi 22zgi

2zgpi

Fig. 2.146FKHPDHFKLYDOHQWGLQSXQFWGHYHGHUHDO]JRPRWXOXLODFRQHFWDUHDîn paralel a rezistoarelor .

&XUHQ LL GH ]JRPRW VXQW PULPL LQGHSHQGHQWH UH]XOWkQG SHQWUX UH]LVWRUXOechivalent,

21

21

RR

RRRp +

= (2.58)

22

21

2zgzgzgp iii += (2.59)

La conectarea în paralel a n rezistoare, zgomotul va fi,

∑=

=n

izgizgp ii

1

22 (2.60)


29

&RQIRUP UHOD LLORU DYkQG vQ YHGHUH FUHúWHUHD ]JRPRWXOXL ODconectarea în serie sau în paralel, aceste variante nu sunt indicate în circuitele înFDUH]JRPRWXOHVWHHVHQ LDO

ÎnFRQFOX]LHRULFHWLSGHUH]LVWRUILHSUH]LQWXQ]JRPRWWHUPLFúLvQSOXVvQIXQF LHGHVWUXFWXUDHOHPHQWXOXLUH]LVWLYSRDWHSUH]HQWDúL]JRPRWGHFXUHQW

5H]LVWRDUHOHFXRVWUXFWXUFULVWDOLQPHWDOLFFXPVXQWFHOHERELQDWHúLFXSHOLFXOPHWDOLF YRU DYHDXQ ]JRPRW UHGXV DYkQGSUHGRPLQDQW ]JRPRW WHUPLF&HOH FX R VWUXFWXU FRPSR]LW FXP VXQW FHOH FX FDUERQ GDU PDL DOHV FHOH FXJOD]XUPHWDOLF úL FXR[L]LPHWDOLFL YRUSUH]HQWDXQ]JRPRWPDLPDUH GDWRULWzgomotului de curent.

În datele de catalog, în general zgomotul este prezentat pe baza factorului dezgomot, pe care-l vom nota cu F, reprezentând raportul dintre tensiunea de zgomotFHDSDUHODERUQHOHUH]LVWRUXOXLúLWHQVLXQHDFRQWLQXDSOLFDW6HH[SULPvQµv/Vsau în dB (decibeli).

În HOHFWULFLWDWH UDSRDUWHOH GLIHULWHORU PDúLQL HOHFWULFH QX VXQW UHSUH]HQWDWHGLUHFW FL ORJDULWPDW 8WLOL]DUHD ORJDULWPLORU UDSRDUWHORU G SRVLELOLWDWHDUHSUH]HQWULLJUDILFHFRQFHQWUDWHDXQRUUDSRDUWHDOHXQRUPULPLFDUHYDULD]vQWUXQ GRPHQLX ODUJ GH FkWHYD GHFDGH vQ FD]XO QRVWUX UH]LVWHQ D 7HQVLXQHD GH]JRPRWvQG%HVWHFRQIRUPUHOD LHL

[ ]VV

VVudBu

zgzg /1

/lg20

µµ

= (2.61a)

6HXWLOL]HD]FDWHQVLXQHGHUHIHULQ µV.Trecerea de la dB la µ9VHIDFHFRQIRUPUHOD LHL

( )( )

2010/

dBU

zg

zg

VVU =µ (2.61b)

ÌQWDEHOXOHVWHGDWFRUHVSRQGHQ DG%µV pentru câteva valori uzuale.

Tabelul 2.8 CRUHVSRQGHQ DG%µV.dB 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40µV/V 10 5,6 3,2 1,8 1 0,56 0,32 0,18 0,1 0,056 0,032 0,018 0,01

=JRPRWXO WHUPLFDUHXQVSHFWUXFRQWLQXXGHIUHFYHQ GHFLYDIL UHJVLW ODRULFHIUHFYHQ ODFDUHOXFUHD]UH]LVWRUXO=JRPRWXOGHFXUHQWQXDUHXQVSHFWUXGHIUHFYHQ FRQWLQXX$PSOLWXGLQHD ]JRPRWXOXL GH FXUHQW HVWH LQYHUV SURSRU LRQDOFX IUHFYHQ D ÌQ IXQF LH GH WLSXO UH]LVWRUXOXL úL GH YDORDUHD UH]LVWHQ HL VH SRDWHDSUR[LPDFDPSOLWXGLQHD]JRPRWXOXLGHFXUHQWGHYLQHHJDOFXFHDD]JRPRWXOXLWHUPLFODRIUHFYHQ GHN+]'HFL]JRPRWXOGHFXUHQWHVWHLPSRUWDQWQXPDLvQGRPHQLXOGHDXGLRIUHFYHQ ODvQDOWIUHFYHQ GHYLQHPXOWPDLPLFGHFkWFHOWHUPLFDVWIHOvQFkWvQDFHVWGRPHQLXGHIUHFYHQ UH]LVWRDUHOHSUH]LQWXQ]JRPRWfoarte redus.

Documents

CAPITOLUL 2 REZISTOARE - CETTI · Conform celor expuse anterior rezistorul liniar fix, pe care-l vom numi ‡UH]LVWRU· UHSUH]LQW XQUH]LVWRUOLQLDUFXUH]LVWHQ DIL[5 FHQXSRDWHIL PRGLILFDW