Linh Kien Dien Tu_DHCT

8/14/2019 Linh Kien Dien Tu_DHCT

1/163

Gio trnh Linh Kinin T

Li ni u

*********

Linh kin in tl kin thc bc u v cn bn ca ngnh in t.

Gio trnh c bin son tcc bi ging ca tc gi trong nhiu nm qua ti KhoaCng Ngh v Cng Ngh Thng Tin, Trngi hc Cn Thv cc Trung Tm Gio dcthng xuyn ng bng sng Cu Long sau qu trnh sa cha v cp nht.

Gio trnh ch yu dng cho sinh vin chuyn ngnh in TVin Thng v TngHa. Cc sinh vin khi Kthut v nhng ai ham thch in tcng tm thy y nhiu iubch.

Gio trnh bao gm 9 chng:

Tchng 1 n chng 3: Nhc li mt skin thc cn bn vvt l vi m, cc mcnng lng v di nng lng trong cu trc ca kim loi v cht bn dn in v dng n nh

cha kha kho st cc linh kin in t.Tchng 4 n chng 8:y l i tng chnh ca gio trnh. Trong cc chng ny,

ta kho st cu to, cchhotng v cc c tnh ch yu ca cc linh kin in tthngdng. Cc linh kin qu c bit v t thng dngc gii thiu ngn gn m khngi vo

phn gii.

Chng 9: Gii thiu shnh thnh v pht trin ca vi mch.

Ngi vit chn thnh cm n anh Nguyn Trung Lp, Ging vin chnh ca B mn VinThng v Tng Ha, Khoa Cng Ngh Thng Tin, Trngi hc Cn Thc kbntho v cho nhiu kin qu bu.

Cn Th, thng 12 nm 2003

Trng Vn Tm

Trang 1 Bin son: Trng Vn Tm


2/163


Mc lc---------

Chng I..........................................................................................................................................................................................4MC NNG LNG V DI NNG LNG.........................................................................................................................4

I. KHI NIM V C HC NGUYN LNG:.................................................................................................................4

II. PHN BIN TTRONG NGUYN TTHEO NNG LNG:.............................................................................6 III. DI NNG L NG: (ENERGY BANDS) ................... ..................... ...................... ..................... ...................... ............... 8

Chng II ................... ...................... ..................... ..................... ...................... ..................... ..................... ...................... ............. 12SDN IN TRONG KIM LOI...........................................................................................................................................12

I. LINH NG V DN XUT:..................................................................................................................................12 II. PHNG PHP KHO ST CHUYN NG CA HT TBNG NNG LNG:............................................14 III. TH NNG TRONG KIM LOI:.....................................................................................................................................15 IV. SPHN B CA IN TTHEO NNG LNG: ..................... ...................... ...................... ...................... ........... 18V. CNG RA (HM CNG): .................... ...................... ..................... ..................... ...................... ..................... ................. 20VI. IN TH TIP XC (TIP TH): ................... ...................... ..................... ...................... ..................... ...................... ..21

Chng III.....................................................................................................................................................................................22CHT BN DN IN ..................... ..................... ...................... ..................... ...................... .................... ....................... ......... 22

I. CHT BN DN IN THUN HAY NI BM: .................... ...................... ...................... ...................... .................. 22II. CHT BN DN NGOI LAI HAY C CHT PHA: ...................... ...................... ...................... ...................... ........... 24

1. Cht bn dn loi N: (N - type semiconductor) ................... ...................... ...................... ...................... ...................... ....242. Cht bn dn loi P:.........................................................................................................................................................253. Cht bn dn hn hp:.....................................................................................................................................................26

III. DN SUT CA CHT BN DN:...............................................................................................................................27 IV. C CH DN IN TRONG CHT BN DN: ................... ...................... ...................... ...................... ...................... 29V. PHNG TRNH LIN TC: ..................... ...................... ..................... ...................... ..................... .................... ........... 30

Chng IV ...................... ..................... ...................... ..................... ..................... ..................... ...................... ...................... ......... 32NI P-N V DIODE.....................................................................................................................................................................32

I. CU TO CA NI P-N:.................................................................................................................................................32II. DNG IN TRONG NI P-N KHI C PHN CC: .............................................................................................341. Ni P-N c phn cc thun:.........................................................................................................................................35

2. Ni P-N khi c phn cc nghch: ...................... ..................... ...................... ..................... ...................... .................... 38III. NH HNG CA NHIT LN NI P-N:..............................................................................................................40IV. NI TR CA NI P-N. ................... ..................... ..................... ...................... ..................... ...................... .................... 41

1. Ni trtnh: (Static resistance). ...................... ..................... ...................... ..................... ...................... .................... .......412. Ni trng ca ni P-N: (Dynamic Resistance)............................................................................................................42

V. IN DUNG CA NI P-N. .................... ..................... ...................... ..................... ..................... ...................... ............. 441. in dung chuyn tip (in dung ni)...........................................................................................................................44 2. in dung khuch tn. (Difusion capacitance) ..................... ...................... ..................... ...................... ...................... ....45

VI. CC LOI DIODE THNG DNG.................................................................................................................................45 1. Diode chnh lu: .................... ..................... ...................... ..................... ...................... ..................... ...................... ......... 452. Diode tch sng. .................... ..................... ...................... ..................... ...................... ..................... ...................... ......... 533. Diode schottky:................................................................................................................................................................53

4. Diode n p (diode Zenner):............................................................................................................................................545. Diode bin dung: (Varicap Varactor diode)..................................................................................................................576. Diode hm (Tunnel diode)...............................................................................................................................................58

Bi tp cui chng ..................... ..................... ...................... ..................... ...................... .................... ....................... ................ 59

Chng V.......................................................................................................................................................................................61TRANSISTOR LNG CC.....................................................................................................................................................61

I. CU TO C BN CA BJT..........................................................................................................................................61II. TRANSISTOR TRNG THI CHA PHN CC. ................... ...................... ...................... ...................... ............... 61III. C CH HOT NG CA TRANSISTOR LNG CC. ...................... ...................... ...................... ...................... .63IV. CC CCH RP TRANSISTOR V LI DNG IN..........................................................................................64 V. DNG IN R TRONG TRANSISTOR. ..................... ...................... ...................... ...................... ...................... ........... 66VI. C TUYN V-I CA TRANSISTOR............................................................................................................................67

1. Mc theo kiu cc nn chung: .................... ...................... ..................... ...................... ..................... ..................... .......... 682. Mc theo kiu cc pht chung. ................... ...................... ..................... ...................... ..................... ..................... .......... 693. nh hng ca nhit ln cc c tuyn ca BJT. ...................... ...................... ...................... ...................... ............... 72

VII. IM IU HNH NG THNG LY IN MT CHIU...............................................................................73 VIII. KIU MU MT CHIU CA BJT. ................... ...................... ...................... ...................... ...................... .................. 78



3/163


IX. BJT VI TN HIU XOAY CHIU..................................................................................................................................80 1. M hnh ca BJT: ...................... ..................... ..................... ...................... ..................... ..................... ...................... ......802. in dn truyn (transconductance) ...................... ..................... ...................... ..................... ...................... .................... 823. Tng trvo ca transistor: ..................... ..................... ...................... ..................... ..................... ..................... .............. 834. Hiu ng Early (Early effect) ..................... ...................... ..................... ...................... ..................... .................... ........... 855. Mch tng ng xoay chiu ca BJT: ................... ...................... ...................... ...................... ...................... .............. 86

Bi tp cui chng ..................... ..................... ...................... ..................... ...................... .................... ....................... ................ 90

CHNG 6 .................... ..................... ...................... ..................... ..................... ...................... ..................... ...................... ......... 91TRANSISTOR TRNG NG..................................................................................................................................................91

I. CU TO CN BN CA JFET:....................................................................................................................................91II. C CH HOT NG CA JFET: ................... ...................... ..................... ...................... ..................... ...................... ..93III. C TUYN TRUYN CA JFET. ...................... ..................... ...................... ..................... ...................... .................... 99IV. NH HNG CA NHIT TRN JFET. ...................... ...................... ...................... ...................... ..................... ..100V. MOSFET LOI HIM (DEPLETION MOSFET: DE MOSFET)...................................................................................102VI. MOSFET LOI T NG (ENHANCEMENT MOSFET: E-MOSFET) ...................... ...................... ...................... .......... 107VII. XC NH IM IU HNH:...................................................................................................................................111VIII. FET VI TN HIU XOAY CHIU V MCH TNG NG VI TN HIU NH........................................113 IX. IN DN TRUYN (TRANSCONDUCTANCE) CA JFET V DEMOSFET........................................................117X. IN DN TRUYN CA E-MOSFET. ................... ...................... ...................... ...................... ...................... ............ 118XI. TNG TR VO V TNG TR RA CA FET. ...................... ...................... ...................... ...................... ................ 119XII. CMOS TUY N TNH (LINEAR CMOS).......................................................................................................................120XIII. MOSFET CNG SUT: V-MOS V D-MOS..............................................................................................................122

1. V-MOS:.........................................................................................................................................................................1222. D-MOS:.........................................................................................................................................................................123

Bi tp cui chng ..................... ..................... ...................... ..................... ...................... .................... ....................... .............. 125

CHNG VII ................... ...................... ..................... ...................... ..................... ..................... ...................... ...................... ...126LINH KIN C BN LP BN DN PNPN V NHNG LINH KIN KHC ...............................................................126

I. SCR (THYRISTOR SILICON CONTROLLED RECTIFIER)...... ...................... ...................... ...................... ............. 1261. Cu to v c tnh: .................. ...................... ..................... ...................... ..................... ...................... ...................... ...1262. c tuyn Volt-Ampere ca SCR:.................................................................................................................................1283. Cc thng s ca SCR: ..................... ..................... ..................... ...................... ..................... ..................... ................... 1294. SCR hot ng in th xoay chiu............................................................................................................................130 5. Vi ng dng n gin: .................... ..................... ..................... ...................... ..................... ...................... .................. 131

II. TRIAC (TRIOD AC SEMICONDUCTOR SWITCH)........... ...................... ...................... ...................... ...................... ..133III. SCS (SILICON CONTROLLED SWITCH). ................... ...................... ...................... ...................... ...................... .....135IV. DIAC ................... ..................... ...................... ..................... ..................... ...................... ..................... ....................... ......136V. DIOD SHOCKLEY..................... ...................... ..................... ...................... ..................... ..................... ....................... ...137VI. GTO (GATE TURN OFF SWITCH). ................... ...................... ...................... ...................... ...................... ................ 138VII. UJT (UNIJUNCTION TRANSISTOR TRANSISTORC NI). ............................................................................140

1. Cu to v c tnh ca UJT:.........................................................................................................................................1402. Cc thng s k thut ca UJT v vn n nh nhit cho nh: ................................................................................1433. ng dng n gin ca UJT:.........................................................................................................................................144

VIII. PUT (Programmable Unijunction Transistor).................................................................................................................145

CHNG VIII............................................................................................................................................................................148LINH KIN QUANG IN T................................................................................................................................................148

I. NH SNG. ..................... ..................... ...................... ..................... ...................... .................... ....................... .............. 148

II. QUANG IN TR (PHOTORESISTANCE)................................................................................................................149 III. QUANG DIOD (PHOTODIODE)....................................................................................................................................151IV. QUANG TRANSISTOR (PHOTO TRANSISTOR). ..................... ...................... ...................... ...................... ................ 152V. DIOD PHT QUANG (LED-LIGHT EMITTING DIODE)................. ...................... ...................... ...................... ......... 154VI. NI QUANG....................................................................................................................................................................155

CHNG IX...............................................................................................................................................................................157SLC V IC ..................... ...................... ..................... ...................... ..................... ..................... ...................... .................. 157

I. KHI NIM V IC - SKT T TRONG H THNG IN T..............................................................................157 II. CC LOI IC. ..................... ...................... ..................... ...................... ..................... ..................... ....................... .......... 159

1. IC mng (film IC):.........................................................................................................................................................1592. IC n tnh th (Monolithic IC):....................................................................................................................................1593. IC lai (hibrid IC)............................................................................................................................................................160

III. S LC V QUI TRNH CH TO MT IC N TINH TH. ..................... ...................... ...................... .............. 160IV. IC S (IC DIGITAL) V IC TNG T(IC ANALOG).............................................................................................1621. IC Digital:......................................................................................................................................................................162

2. IC analog: ................... ...................... ..................... ...................... ..................... ...................... ..................... .................. 163Ti liu tham kho ................... ...................... ..................... ...................... ..................... ...................... ..................... .................. 163



4/163


Chng I

MC NNG LNG V DI NNG LNGTrong chng ny ch yu nhc li cc kin thc cbn v chc nguyn lng,

s phn bin t trong nguyn t theo nng lng, t hnh thnh di nng lngtrong tinh th cht bn dn. hc chng ny, sinh vin ch cn c kin thc tng iv vt l v ha hc i cng. Mc tiu cn t c l hiu c ngha ca di dnin, di ha tr v di cm, t phn bit c cc cht dn in, bn dn in v cchin.

I. KHI NIM V CHC NGUYN LNG:

Ta bit rng vt cht c cu to t nhng nguyn t ( l thnh phn nh nht

ca nguyn t m cn gi nguyn tnh cht ca nguyn t). Theo m hnh ca nh vtl Anh Rutherford (1871-1937), nguyn t gm c mt nhn mang in tch dng(Proton mang in tch dng v Neutron trung ho vin) v mt sin t (electron)mang in tch m chuyn ng chung quanh nhn v chu tc ng bi lc ht ca nhn.

Nguyn t lun lun trung ha in tch, s electron quay chung quanh nhn bng sproton cha trong nhn - in tch ca mt proton bng in tch mt electron nhng tridu). in tch ca mt electron l -1,602.10-19Coulomb, iu ny c ngha l c c1 Coulomb in tch phi c 6,242.1018 electron. in tch ca in t c tho c trctip nhng khi lng ca in t khng tho trc tip c. Tuy nhin, ngi ta ctho c t s gia in tch v khi lng (e/m), t suy ra c khi lng ca

in t l:

mo=9,1.10-31Kg

l khi lng ca in t khi n chuyn ng vi vn tc rt nh so vi vn tcnh sng (c=3.108m/s). Khi vn tc in t tng ln, khi lng ca in tc tnhtheo cng thc Lorentz-Einstein:

2

2

o

c

v1

m

=e

m

Mi in t chuyn ng trn mt ng trn v chu mt gia tc xuyn tm. Theothuyt in t th khi chuyn ng c gia tc, in t phi pht ra nng lng. S mtnng lng ny lm cho quo ca in t nh dn v sau mt thi gian ngn, in ts ri vo nhn. Nhng trong thc t, cc h thng ny l mt h thng bn theo thigian. Do , gi thuyt ca Rutherford khng ng vng.

Nh vt l hc an Mch Niels Bohr (1885- 1962) b tc bng cc gi thuytsau:



5/163


C nhng quo t bit, trn in t c th di chuyn m khng pht ra nnglng. Tng ng vi mi quo c mt mc nng lng nht nh. Ta c mt quodng.

Khi in t di chuyn t mt quo tng ng vi mc nng lng w1 sang quo khc tng ng vi mc nng lng w2 th s c hin tng bc x hay hp thu nnglng. Tn s ca bc x (hay hp thu) ny l:

h

wwf 12

=

Trong , h=6,62.10-34 J.s (hng s Planck).

Trong mi quo dng, moment ng lng ca in t bng bi s ca h=2h

Moment ng lng: hn2

h.nr.v.m =

=

r

+e

-e

v

Hnh 1

Vi gi thuyt trn, ngi ta don c cc mc nng lng ca nguyn thydro v gii thch c quang ph vch ca Hydro, nhng khng gii thch c i vinhng nguyn t c nhiu in t. Nhn thy s i tnh gia sng v ht, Louis deBroglie (Nh vt l hc Php) cho rng c th lin kt mi ht in khi lng m, chuyn

ng vi vn tc v mt bc sngmvh= .

Tng hp tt c gi thuyt trn l mn chc nguyn lng, kh dc th gii thchc cc hin tng quan st c cp nguyn t.

Phng trnh cn bn ca mn c hc nguyn lng l phng trnh Schrodingerc vit nh sau:

0)UE(m.2

2

=+

h

l ton t Laplacien



6/163


7/163


Tng L c ti a 8 in t.

Tng M c ti a 18 in t.

Tng N c ti a 32 in t.

Cc tng O,P,Q cng c 4 ph tng v cng c ti a 32 in t.

ng vi mi ph tng c mt mc nng lng v cc mc nng lng c xptheo th t nh sau:

1 2 3 4 5 6 7

1s 2s 3s 4s 5s 6s 7s

2p 3p 4p 5p

6d

7p

3d 4d

5f

6p

7d

4f

5d

6f 7f

Hnh 2

Khi khng b kch thch, cc trng thi nng lng nh bin t chim trc (gnnhn hn) khi ht ch mi sang mc cao hn (xa nhn hn). Th d: nguyn t Na c sin t z=11, c cc ph tng 1s,2s,2p b cc in t chim hon ton nhng ch c 1in t chim ph tng 3s.

Cch biu din:Theo mu ca Bohr Theo mc nng lng

NATRI Na11 1s2 2s2 2p6 3s1

Na 2-8-1

Na+11



8/163


SILICIUM Si14 1s2 2s2 2p6 3s2 3p2

Si 2-8-4

Si+14

GERMANIUM Ge32

1s2

2s2

2p6

3s2

3p6

4s2

3d10

4p2

Ge 2-8-18-4

Ge+32

Hnh 3

Lp bo ha: Mt ph tng bo ha khi c sin t ti a.

Mt tng bo ha khi mi ph tng bo ha. Mt tng bo ha rt bn, khng

nhn thm v cng kh mt in t.

Tng ngoi cng: Trong mt nguyn t, tng ngoi cng khng bao gicha qu 8in t. Nguyn t c 8 in ttng ngoi cng u bn vng (trng hp cc kh tr).

Cc in ttng ngoi cng quyt nh hu ht tnh cht ha hc ca mt nguynt.

III. DI NNG LNG: (ENERGY BANDS)

Nhng cng trnh kho cu tia X chng t rng hu ht cc cht bn dn u dng kt tinh.



9/163


Ta xt mt mng tinh th gm N nguyn t thuc nhm 4A, th d C6. Ta tngtng rng c th thay i c khong cch gia cc nguyn t m khng thay i cuto cn bn ca tinh th. Nu cc nguyn t cch nhau mt khong d1 sao cho tc ngln nhau khng ng k th cc mc nng lng ca chng trng vi cc mc nng lngca mt nguyn t c nht. Hai ph tng ngoi cng c 2 in t s v 2 in t p(C6=1s22s22p2). Do , nu ta khng n cc tng trong, ta c 2N in t chim ttc 2N trng thi s v c cng mc nng lng; Ta cng c 2N in t p chim 2N trngthi p. Vy c 4N trng thi p cha b chim. Gi s khong cch gia cc nguyn tc thu nh hn thnh d2, tc dng ca mt nguyn t bt k ln cc nguyn t ln cntrthnh quan trng.

Nng lng E4N trng thi 6N trng thi pcha b chim Di dn in (2N trng thi b chim)

2p

Di cm EG Di cm

4N trng thi b chim 2s2N trng thi s

Di ha tr b chim

d0 d4 d3 d2 d1

Hnh 4

Ta c mt h thng gm N nguyn t, do cc nguyn t phi tun theo nguyn lPauli. 2N in t s khng th c cng mc nng lng m phi c 2N mc nng lngkhc nhau; khong cch gia hai mc nng kng rt nh nhng v N rt ln nn khongcch gia mc nng lng cao nht v thp nht kh ln, ta c mt di nng lng. 2Ntrng thi ca di nng lng ny u b 2N in t chim. Tng t, bn trn di nnglng ny ta c mt di gm 6N trng thi p nhng ch c 2N trng thi p b chim ch.

Ta rng, gia hai di nng lng m in t chim-c c mt di cm. int khng th c nng lng nm trong di cm, khong cch (di cm) cng thu hp khikhong cch d cng nh (xem hnh). Khi khong cch d=d3, cc di nng lng chngln nhau, 6N trng thi ca di trn ho vi 2N trng thi ca di di cho ta 8N trngthi, nhng ch c 4N trng thi b chim. khong cch ny, mi nguyn t c 4 in ttng ngoi nhng ta khng th phn bit c in t no l in t s v in t no lin t p, khong cch t, tc dng ca cc nguyn t ln nhau rt mnh. S phn



10/163


b cc di nng lng tu thuc vo dng tinh th v nguyn t s. Ngi ta xc nh sphn b ny bng cch gii phng trnh Schrodinger v c kt qu nh hnh v. Ta cmt di ho tr (valence band) gm 4N trng thi hon ton b chim v mt di dn in(conduction band) gm 4N trng thi cha b chim. Gia hai di nng lng ny, c mtdi nng lng cm c nng lng khong 6eV. (eV: ElectronVolt)

1 volt l hiu in th gia hai im ca mt mch in khi nng lng cung cp l1 Joule chuyn mt in tch 1 Coloumb tim ny n im kia.

Vy,Joule

ColoumbQ

WVvolt

=

Vy nng lng m mt in t tip nhn khi vt mt hiu in th 1 volt l:

Q

WV =

19-10.602,1

WV1 =

Joule10.602,1W 19=

Nng lng ny c gi l 1eV (1eV=1,602.10-19J)

Ta kho st trng hp c bit ca tinh th Cacbon. Nu ta kho st mt tinh thbt k, nng lng ca in t cng c chia thnh tng di. Di nng lng cao nht bchim gi l di ha tr, di nng lng thp nht cha b chim gi l di dn in. Ta

c bit ch n hai di nng lng ny.

E Nng lng

Di dn in (Di nng lngthp nht cha b chim)

EG Di cm

Di ho tr (Di nng lng

cao nht b chim)

Hnh 5

* Ta c 3 trng hp:



11/163


Di cm c cao kh ln (EG>5eV). y l trng hp ca cc cht cch in. Thd nh kim cng c EG=7eV, SiO2 EG=9eV.

Di cm c cao nh (EG5eV Di cm Di dn in

EG


12/163


Chng II

SDN IN TRONG KIM LOINi dung chnh ca chng ny l n li khi nim v linh ng ca in t, dn

sut ca kim loi, t a ra phng php kho st chuyn ng ca ht t bng nnglng. Mc tiu cn t c l hiu r th nng ca in t trong kim loi, s phn bin t theo nng lng, cng ra ca kim loi v tip th.

I. LINH NG V DN XUT:

Trong chng I, hnh nh ca di nng lng trong kim loi c trnh by.Theo s kho st trn, di nng lng do in t chim c th cha y v khng c dicm cho nhng nng lng cao. Ngha l in t c th di chuyn t do trong kim loi

di tc dng ca in trng.

Na

Hnh 1

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

E

Hnh trn v phn bin tch trong tinh th Na. Nhng ch gch cho tiu biu chonhng in tdi ha tr c nng lng thp nht, nhng ch trng cha nhng in tc nng lng cao nm trong di dn in. Chnh nhng in t ny l nhng in tkhng th ni thuc hn vo mt nguyn t nht nh no v c th di chuyn t do tnguyn t ny sang nguyn t khc. Vy kim loi c coi l ni cc ion kt hp chtch vi nhau v xp u n trong 3 chiu trong mt m my in t m trong int c th di chuyn t do.

Hnh nh ny l s m t kim loi trong cht kh in t. Theo thuyt cht kh int kim loi, in t chuyn ng lin tc vi chiu chuyn ng bin i mi ln vachm vi ion dng nng, c xem nhng yn. Khong cch trung bnh gia hai lnva chm c gi l on ng t do trung bnh. V y l chuyn ng tn lon, nn mt thi im no , sin t trung bnh qua mt n v din tch theo bt c chiuno s bng sin t qua n v din tch y theo chiu ngc li. Nh vy , dng intrung bnh trit tiu.



13/163


Gi s, mt in trng Ec thit lp trong mng tinh th kim loi, ta th khost chuyn ng ca mt in t trong t trng ny.

ene1 e2

x

Hnh 2

Hnh trn m t chuyn ng ca in t di tcdng ca in trng E. Quoca in t l mt ng g p khc v in t chm vo cc ion dng v i hngchuyn ng. Trong thi gian t=n ln thi gian t do trung bnh, in t di chuyn c

mt on ng l x. Vn tct

xv = gi l vn tc trung bnh. Vn tc ny t l vi in

trng E. Ev =

Hng s t l gi l linh ng ca in t, tnh bng m2/Vsec.in tch i qua mi n v din tch trong mt n v thi gian c gi l mt dngin J.Ta c: J = n.e.vTrong , n: mt in t, e: in tch ca mt electron

By gi, ta xt mt in tch vi cp S t thng gc vi chiu di chuyn ca in t.Nhng in t ti mt S thi im t=0 (t=0 c chn lm thi im gc) l nhngin t trn mt S cch S mt khong v (vn tc trung bnh ca in t) thi imt=-1. thi im t=+1, nhng in ti qua mt S chnh l nhng in t cha tronghnh tr gii hn bi mt S v S. in tch ca sin t ny l q=n.e.v.s, vi n l mtin t di chuyn. Vy in tch i ngang qua mt n v din tch trong mt n vthi gian l: J=n.e.v t = -1 t = 0

S S

v

Hnh 3

Nhng nnEv = E..e.nJ =

Ngi ta t = .e.n (c l Sigma)

Nn EJ = gi l dn xut ca kim loi

V

=1

gi l in trsut ca kim loi

in trsut tnh bng m v dn sut tnh bng mho/m



14/163


II. PHNG PHP KHO ST CHUYN NG CAHT TBNG NNG LNG:

K A5cm

v0M(x)

0 EC = 2eV -10V

+

Hnh 4

Phng php kho st ny cn c trn nh lut bo ton lng. d hiu, ta xtth d sau y:

Mt diode l tng gm hai mt phng song song bng kim loi cch nhau 5 Cm.Anod A c hiu in th l 10V so vi Catod K. Mt in t ri Catod K vi nnglng ban u Ec=2eV. Tnh khong cch ti a m in t c th ri Catod.

Gi s, in t di chuyn ti im M c honh l x. in th ti im M s t lvi honh x v in trng gia Anod v Catod u.

in th ti mt im c honh x l:+= xV

Khi x=0, (ti Catod) 00V ==

Nn xV =

Ti x=5 Cm (ti Anod A) th V=-10volt 2=

Vy V=-2x (volt) vi x tnh bng CmSuy ra th nng ti im M l:

(Joule)x.e.2QVU +== vi e l in tch ca in t.

Ta c th vit (eV)x.2U =

Nng lng ton phn ti im M l:

Umv21T2 +=



15/163


Nng lng ny khng thay i. Trn th, T c biu din bng ng thngsong song vi trc x.

Hiu 2mv2

1UT = l ng nng ca in t. ng nng ny ti a ti im O

(Catod) ri gim dn v trit tiu ti im P c honh x0. Ngha l ti im x0, in tdng li v di chuyn trv catod K. Vy x0 l khong cch ti a m in t c th rixa Catod.

eV (Nng lng)

P

T

20v.m21

0 x0 = 1cm 5 cm x (cm)

Hnh 5

Ti im M (x=x0) ta c:

T-U=0

M T=+Ec (nng lng ban u)

T=2.e.V

Vy, U=2.x0 (eV)

=> 2-2.x0=0 => x0=1Cm

V phng din nng lng, ta c th ni rng vi nng lng ton phn c sn T,

in t khng th vt qua ro th nng U vo phn c gch cho.Ta thy rng nu bit nng lng ton phn ca ht in v s phn b th nng

trong mi trng ht in, ta c th xc nh c ng di chuyn ca ht in.

Phn sau y, ta p dng phng php trn kho st s chuyn ng ca in ttrong kim loi.

III. TH NNG TRONG KIM LOI:

Nu ta c mt nguyn t duy nht th in th ti mt im cch mt khong rl:



16/163


Cr

kV +=

Nu chn in th ti mt im rt xa lm in th Zero th C=0. Vy mt in tc in tch e cch nhn mt on r s c th nng l:

rkeeVU ==

-e U -e

r

0 r

Hnh 6

Hnh trn l th ca th nng U theo khong cch r. Phn th khng lin tcng vi mt in tbn tri nhn . Nu ta c hai nhn v th trong vng gia hainhn ny th nng ca in t l tng cc th nng do v to ra. Trong kim loi, cc

nhn c sp xp u n theo 3 chiu. Vy, ta c th kho st s phn b ca th nngbng cch xt s phn b dc theo di , v ...



17/163


Hnh trn biu din s phn b.

U in t t do0

EB

U0

in t buc

V0 = 0 EB

Hnh 7

+

Ta thy rng c nhng vng ng th rng nm xen k vi nhng vng in ththay i rt nhanh. Mt ngoi ca mi kim loi khng c xc nh hon ton v cchnhn cui cng mt khong cch nh. V bn phi ca nhn khng cn nhn nn thnng tin ti Zero ch khng gi tnh tun hon nh bn trong kim loi. Do , ta c mtro th nng ti mt ngoi ca kim loi.

Ta xt mt in t ca nhn v c nng lng nh hn U0, in t ny ch c thdi chuyn trong mt vng nh cnh nhn gia hai ro th nng tng ng. l in t

buc v khng tham gia vo s dn in ca kim loi. Tri li, mt in t c nng lngln hn U0 c th di chuyn t nguyn t ny qua nguyn t khc trong khi kim loi

nhng khng th vt ra ngoi khi kim loi c v khi n mt phn cch, in tng vo ro th nng. Cc in t c nng lng ln hn U0c gi l cc in t tdo. Trong cc chng sau, ta t bit ch n cc in t ny.

V hu ht khi kim loi u c cng in th V0 tng ng vi th nng U0=-eV0nn ta c th gi s khi kim loi l mt khi ng th V0. Nhng in th ty thuc vomt hng s cng nn ta c th chn V0 lm in th gc (V0=0V). Gi EB l chiu caoca ro th nng gia bn trong v bn ngoi kim loi. Mt in t bn trong khi kimloi mun vt ra ngoi phi c t nht mt nng lng U=EB, v vy ta cn phi bit s

phn b ca in t theo nng lng.



18/163


III. SPHN B CA IN TTHEO NNG LNG:

Gi nE= l s in t trong mt n v th tch c nng lng t E n E+E.

Theo nh ngha, mt in t trung bnh c nng lng t E n E+E l t sE

n E

.

Gii hn ca t s ny khi gi l mt in t c nng lng E.0E

Ta c: (1)dE

dn

E

nlim)E( EE

0E=

=

Vy, (2)dE).E(dn E =

Do , nu ta bit c hm s )E( ta c th suy ra c sin t c nng lngtrong khong t E n E+dE bng biu thc (2). Ta thy rng (E) chnh l s trng thinng lng E b in t chim. Nu gi n(E) l s trng thi nng lng c nng

lng E m in t c th chim c. Ngi ta chng minh c rng: t s)E(n)E( bng

mt hm s f(E), c dng:

KT

EE F

e1

1

)E(n

)E()E(f

+

=

=

Trong , K=1,381.10-23 J/0K (hng s Boltzman)

K)(V/10.62,8e10.381,1K 05

23 ==

EF nng lng Fermi, ty thuc vo bn cht kim loi.

Mc nng lng ny nm trong di cm.

nhit rt thp (T00K)

Nu EEF, ta c f(E)=0

Vy f(E) chnh l xc sut tm thy in t c nng lng E nhit T.

Hnh sau y l th ca f(E) theo E khi T00K v khi T=2.5000K.

Trang 1 Bin so8 n: Trng Vn Tm

f(E) 1 T=00K

T=25000K

EF E

Hnh 8

(E)T=00K

T=25000K

EF E


19/163


Ta chp nhn rng:

2E.)E(N =1

l hng s t l.

Lc , mt in t c nng lng E l:

)E(f.2

1E.)E(N).E(f)E( ==

Hnh trn l th ca (E) theo E tng ng vi nhit T=00K v T=2.5000K.

Ta thy rng hm (E) bin i rt t theo nhit v ch bin i trong vng cnca nng lng EF. Do , nhit cao (T=2.5000K) c mt s rt t in t c nng

lng ln hn EF, hu ht cc in tu c nng lng nh hn EF. Din tch gii hnbi ng biu din ca (E) v trc E cho ta sin t t do n cha trong mt n vth tch.

===FF E

0

2

3

F2

1E

0

E.3

2dE.E.dE).E(n

( l f(E)=1 v T=0

0

K)Ty ta suy ra nng lng Fermi EF

3

2

F

n.

2

3E

=

Nu ta dng n v th tch l m3 v n v nng lng l eV th c tr s l:

= 6,8.1027

Do , 32

19F n.10.64,3E

=

Nu bit c khi lng ring ca kim loi v sin t t do m mi nguyn tc th nh ra, ta tnh c n v t suy ra EF. Thng thng EF < 10eV.

Th d, khi lng ring ca Tungsten l d = 18,8g/cm3, nguyn t khi l A = 184,bit rng mi nguyn t cho v = 2 in t t do. Tnh nng lng Fermi.

Gii: Khi lng mi cm3

l d, vy trong mt cm3

ta c mt s nguyn t khi ld/A. Vy trong mi cm3, ta c s nguyn t thc l:



20/163


0A.A

dvi A0 l s Avogadro (A0 = 6,023.10

23)

Mi nguyn t cho v = 2 in t t do, do sin t t do trong mi m3 l:

6

0 10.v.A.A

d

n =

Vi Tungsten, ta c:

10.23,110.2.10.203,6.184

8,18n 29623 = in t/m3

( )32

2919F 10.23,1.10.64,3E

=

eV95,8EF

IV. CNG RA (HM CNG):

Ta thy rng nhit th p (T #00K), nng lng ti a ca in t l EF(E


21/163


KT

E2

0th

w

eTAJ

= Trong , A0 = 6,023.1023 v K = 1,38.10-23 J/0K

y l phng trnh Dushman-Richardson.

Ngi ta dng phng trnh ny o EW v ta c tho c dng in Jth; dng

in ny chnh l dng in bo ha trong mt n hai cc chn khng c tim lm bngkim loi mun kho st.

V. IN TH TIP XC (TIP TH):

Xt mt ni C gia hai kim loi I v II. Nu ta dng mt Volt k nhy o hiuin th gia hai u ca ni (A v B), ta thy hiu sin th ny khng trit tiu, theonh ngha, hiu in th ny gi l tip th. Ta gii thch tip th nh sau:

A B I II

I II A B

V V

Hnh 10

iE

EW1 EW2 Ew1 < Ew2A > VB

+ -

+

+

+

+

+

+

+

+

+

+

+

+

+

+

-

------

-

------

Gi s kim loi I c cng ra EW1 nh hn cng ra EW2 ca kim loi II. Khi ta ni haikim loi vi nhau, in t s di chuyn t (I) sang (II) lm cho c s t tp in t bn(II) v c s xut hin cc Ion dng bn (I). Cch phn bin tch nh trn to ra mtin trng Ei hng t (I) sang (II) lm ngn tr s di chuyn ca in t. Khi Eimnh, cc in t khng di chuyn na, ta c s cn bng nhit ng hc ca h thnghai kim loi ni vi nhau. S hin hu ca in trng Ei chng t c mt hiu in thgia hai kim loi.



22/163


Chng III

CHT BN DN IN(SEMICONDUCTOR)

Trong chng ny ni dung chnh l tm hiu k cu trc v c im ca cht bndn in, cht bn dn loi N, cht bn dn loi P v cht bn dn tng hp. Kho st nhhng ca nhit ln cht bn dn, t hiu c cch dn in trong cht bn dn.y l vt liu cbn dng trong cng ngh ch to linh kin in t, sinh vin cn nmvng c th hc tt cc chng sau.

I. CHT BN DN IN THUN HAY NI BM:

(Pure semiconductor or intrinsic semiconductor)

Hu ht cc cht bn dn u c cc nguyn t sp xp theo cu to tinh th. Haicht bn dn c dng nhiu nht trong k thut ch to linh kin in t l Silicium vGermanium. Mi nguyn t ca hai cht ny u c 4 in tngoi cng kt hp vi 4in t ca 4 nguyn t k cn to thnh 4 lin kt ha tr. V vy tinh th Ge v Si nhit thp l cc cht cch in.

in t trong

di ha tr

Ni ha tr

Hnh 1: Tinh th cht bn dn nhit thp (T = 00K)

Nu ta tng nhit tinh th, nhit nng s lm tng nng lng mt sin t vlm gy mt s ni ha tr. Cc in tcc ni b gy ri xa nhau v c th di chuynd dng trong mng tinh th di tc dng ca in trng. Ti cc ni ha tr b gy tac cc l trng (hole). V phng din nng lng, ta c th ni rng nhit nng lm tngnng lng cc in t trong di ha tr.



23/163


in t t do trong

di dn in

Ni ha trb gy.

L trng trongdi ha tr

Hnh 2: Tinh th cht bn dn nhit cao (T = 3000K)

Khi nng lng ny ln hn nng lng ca di cm (0,7eV i vi Ge v 1,12eVi vi Si), in t c th vt di cm vo di dn in v cha li nhng l trng (trngthi nng lng trng) trong di ha tr). Ta nhn thy sin t trong di dn in bngs l trng trong di ha tr.

Nu ta gi n l mt in t c nng lng trong di dn in v p l mt ltrng c nng lng trong di ha tr. Ta c:n=p=ni

Ngi ta chng minh c rng:

ni2 = A0.T

3. exp(-EG/KT)Trong : A0 : S Avogadro=6,203.10

23

T : Nhit tuyt i ( Kelvin)K : Hng s Bolzman=8,62.10-5 eV/0K

EG : Chiu cao ca di cm.E

Di dn in in t trongdi dn in

Mc fermi

Di ha tr L trng trongDi ha tr

nhit thp (00K) nhit cao (3000K)

Hnh 3

Ta gi cht bn dn c tnh cht n=p l cht bn dn ni bm hay cht bn dnthun. Thng thng ngi ta gp nhiu kh khn ch to cht bn dn loi ny.



24/163


II. CHT BN DN NGOI LAI HAY C CHT PHA:

(Doped/Extrinsic Semiconductor)

1. Cht bn dn loi N: (N - type semiconductor)

Gi s ta pha vo Si thun nhng nguyn t thuc nhm V ca bng phn loi tunhon nh As (Arsenic), Photpho (p), Antimony (Sb). Bn knh nguyn t ca As gn

bng bn knh nguyn t ca Si nn c th thay th mt nguyn t Si trong mng tinh th.Bn in t ca As kt hp vi 4 in t ca Si ln cn to thnh 4 ni ha tr, Cn d limt in t ca As. nhit thp, tt c cc in t ca cc ni ha tru c nnglng trong di ha tr, tr nhng in t tha ca As khng to ni ha tr c nnglng ED nm trong di cm v cch dy dn in mt khang nng lng nh chng

0,05eV.

trong di cm

0,05eV

in t tha ca As

Hnh 4: Tinh th cht bn dn nhit cao (T = 300

Gi s ta tng nhit ca tinh th, mt s ni ha tr b gy, ta c nhng l trngtrong di ha tr v nhng in t trong di dn in ging nh trong trng hp ca cccht bn dn thun. Ngoi ra, cc in t ca As c nng lng ED cng nhn nhit nng trthnh nhng in t c nng lng trong di dn in. V th ta c th coi nh huht cc nguyn t As u b Ion ha (v khang nng lng gia ED v di dn in rtnh), ngha l tt c cc in t lc u c nng lng EDu c tng nng lng trthnh in t t do.


in t tha ca As E

1,12eV Mc fermi tng

0K) nhit T = 00K

Si Si Si

Si As Si

Si Si Si

Di ha tr

E Di dn in

Di ha tr

Hnh 5

Di dn in


25/163


Nu ta gi ND l mt nhng nguyn t As pha vo (cn gi l nhng nguyn tcho donor atom).

Ta c: n = p + ND

Vi n: mt in t trong di dn in.P: mt l trng trong di ha tr.

Ngi ta cng chng minh c: n.p = ni2 (n


26/163


Nu ta gi NA l mt nhng nguyn t In pha vo (cn c gi l nguyn tnhn), ta cng c:

p = n + NAp: mt l trng trong di ha tr.n: mt in t trong di dn in.

Ngi ta cng chng minh c:

n.p = ni2 (p>n)

ni l mt in t hoc l trng trong cht bn dn thun trc khi pha.

Cht bn dn nh trn c s l trng trong di ha tr nhiu hn sin t trong didn in c gi l cht bn dn loi P.

Nh vy, trong cht bn dn loi p, ht ti in a s l l trng v ht ti in thius l in t.

3. Cht bn dn hn hp:

Ta cng c th pha vo Si thun nhng nguyn t cho v nhng nguyn t nhn c cht bn dn hn hp. Hnh sau l s nng lng ca cht bn dn hn hp.


Di dn in

ED ND ED

EA NA EA

Di ha tr

nhit thp nhit cao(T = 00K) (T = 3000K)

Hnh 8


27/163


Trong trng hp cht bn dn hn hp, ta c:

n+NA = p+NDn.p = ni

2

Nu ND > NA => n>p, ta c cht bn dn hn hp loi N.Nu ND < NA => n


28/163


Vy ta c th coi nh dng in trong cht bn dn l s hp thnh ca dng indo nhng in t trong di dn in (a si vi cht bn dn loi N v thiu si vicht bn dn loi P) v nhng l trng trong di ha tr (a si vi cht bn dn loi Pv thiu si vi cht bn dn loi N).

Dng in t trong Dng in t trongdi dn in di dn in

Cht bn dn thun

Dng in t Dng l trngtrong di ha tr

+ - + -V V

Hnh 11

Tng ng vi nhng dng in ny, ta c nhng mt dng in J, Jn, Jp saocho: J = Jn+Jp

Ta chng minh c trong kim loi:

J = n.e.v = n.e..E

Tng t, trong cht bn dn, ta cng c:

Jn=n.e.vn=n.e. n.E (Mt dng in tri ca in t, n l linh ng ca in t,n l mt in t trong di dn in)

Jp=p.e.vp=p.e.p.E (Mt dng in tri ca l trng, p l linh ng ca ltrng, p l mt l trng trong di ha tr)

Nh vy: J=e.(n.n+p.p).E

Theo nh lut Ohm, ta c:

J = .E=> = e.(n.n+p.p)c gi l dn sut ca cht bn dn.



29/163


Trong cht bn dn loi N, ta c n>>p nn n = n.n.eTrong cht bn dn loi P, ta c p>>n nn p = n.p.e

IV. CCH DN IN TRONG CHT BN DN:

Di tc dng ca in trng, cc in t v l trng di chuyn vi vn tc trungbnh vn=n.E v vp=p.E.

Sin t v l trng di chuyn thay i theo mi thi im, v ti mi thi im cmt sin t v l trng c sinh ra di tc dng ca nhit nng. Sin t sinh ratrong mi n v thi gian gi l tc sinh to g. Nhng in t ny c i sng trung

bnh n v trong khi di chuyn in t c th gp mt l trng c cng nng lng v tihp vi l trng ny. Nu gi n l mt in t, trong mt n v thi gian sin t bmt i v s ti hp l n/n. Ngoi ra, trong cht bn dn, s phn b ca mt in tv l trng c th khng u, do c s khuch tn ca in t t vng c nhiu in t

sang vng c t in t.Xt mt mu bn dn khng u c mt in tc phn b nh hnh v. Ti

mt im M trn tit din A, sin ti ngang qua tit din ny (do s khuch tn) t lvi dn/dx, vi din tch ca in t v vi tit din A.

M vkt

xHnh 12

Dng in khuch tn ca in ti qua A l:0A

dx

dn.e.DIn nkt =

V mt dng in khuch tn ca l trng l:



30/163


dx

dp.D.eJp pkt =

Ngi ta chng minh c rng:

600.11

TV

e

KTDDT

n

n

p

p ===

=

Vi: K l hng s Boltzman = 1,382.10-23J/0KT l nhit tuyt i.

H thc ny c gi l h thc Einstein. nhit bnh thng (3000K): VT=0,026V=26mV

V. PHNG TRNH LIN TC:

Xt mt hnh hp c tit din A, chiu di dx t trong mt mu bn dn c dngin l trng Ip i qua. Ti mt im c honh x, cng dng in l Ip. Ti mtc honh l x+dx, cng dng in l Ip+dIp. Gi P l mt l trng trong hnh

hp, p l i sng trung bnh ca l trng. Trong mi giy cp

p

l trng b mt i do s

ti hp. Vy mi giy, in tch bn trong hp gim i mt lng l:

p1

p.dx.A.eG

= (do ti hp)

ng thi in tch trong hp cng mt i mt lng:G2=dIp (do khuch tn).

Gi g l mt l trng c sinh ra do tc dng nhit, trong mi giy, in tch trong hptng ln mt lng l:

dx

A

Ip Ip+dIp

x+dx

x x

Ip

Hnh 13

T1=e.A.dx.gVy in tch trong hp bin thin mt lng l:

dIpp

.dx.A.eg.dx.A.e)GG(Tp

211 =+

bin thin bng:dt

dp.dx.A.e

Vy ta c phng trnh:

A.e

1.

dx

dIppg

dt

dp

p

= (1)

Nu mu bn dn trng thi cn bng nhit v khng c dng in i qua, ta c:



31/163


;0dt

dp= dIp=0; P=P0=hng s

Phng trnh (1) cho ta:

pp

gg0

=

=

Vi P l mt l trng trng thi cn bng nhit. Thay tr s ca g vo phng trnh

0Pp

0

(1) v rng p v IP vn ty ian v khong cch x, phng trnh (1) trthnh:thuc vo thi g

eA.

xt p

0

=

1Ippp p (2)

Gi l phng trnh lin tc.

n, ta c:T in t Ing t vi dng

eA

1.

Innn n0

(3)xt n

=

ii ph tr h lin tc trong trdng in Ip l dng in khuch tn c

Ta c:

TD: ta g ng n ng hp p khng ph thuc vo thi gian va l trng.

dx

dp.eA.DI p0dt

dp= v p =

Do ,2

2

p dx

pd.eA.D

dIp=

dxPhng trng (2) trthnh:

pL.Ddx 2pp2

PPPPpd2 00 ==

Trong , ta tppp

.DL =

Nghim h (4) l:s ca phng trn

x

+ ppL

x

L e.AeA

ng nn A1 = 0

Do :

P-P0P(x0)-P0

x

Hnh 14

P-P0

P(x0)-P0

x0 x

Hnh 15

x0

= 10 .PP 2V mt l trng khng th tng khi x t

= pL

x

20 e.APP ti x = x0.

Mt l trng l p(x0),

Do :

=pL

x

200 e.AP)x(P Suy ra, nghim ca phng trnh (4) l:

[ ]

= p0

L

xx

000 e.P)x(PP)x(P



32/163


33/163


cng, ngi ta ph kim loi ln cc vng p v n+ v hn dy ni ra ngoi. Ta c mtni P-N c mt ni gia vng p v n+ thng.

Khi ni PN c thnh lp, cc l trng trong vng P khuch tn sang vng N vngc li, cc in t trong vng N khuch tn sang vng P. Trong khi di chuyn, ccin t v l trng c th ti hp vi nhau. Do , c s xut hin ca mt vng hai

bn mi ni trong ch c nhng ion m ca nhng nguyn t nhn trong vng P vnhng ion dng ca nguyn t cho trong vng N. cc ion dng v m ny to ra mtin trng Ej chng li s khuch tn ca cc ht in, ngha l in trng Ei s to ramt dng in tri ngc chiu vi dng in khuch tn sao cho dng in trung bnhtng hp trit tiu. Lc , ta c trng thi cn bng nhit. Trn phng din thng k, tac th coi vng c nhng ion cnh l vng khng c ht in di chuyn (khng c int t do vng N v l trng vng P). Ta gi vng ny l vng khim khuyt hay vnghim (Depletion region). Tng ng vi in trng Ei, ta c mt in th V0hai bnmt ni, V0c gi l ro in th.

P NV0

- +

x1 Ei x2

V0= Ro in thTi mi ni

x1 0 x2

Hnh 2

-

-

-

+

+

+

+

+

---

-

++

Tnh V0: ta n dng in khuch tn ca l trng:

0dx

.D.eJ ppkt >= dp

v dng in tri c trng:

, ta c:

a l0E..p.eJ ipptr


34/163


Hay l: ipp E..p.edxdp

.D.e =

dx.Ep

dp.

Dp ip

=

e

KT

V

DTM p

p

==

Vdx

dVE i

=

Do :p

dp.VdV T=

Ly tch phn 2 v x1n x2 v rng ti x1in thc chn l 0volt, mt l g mt Ppovng P lc cn bng. Ti x2, in th l V0 v mt l trngl Pno n N lc cn bng.

ttrn lv g

=on

oP

0V P

PT p

dpVdV

0

M: APD

in NPvN

Poo

2n

Nn:

=

o

o

n

P

T0 P

PlogVV

Hoc: 2i

0 ne

= ADNN

logKT

V

Tng t nh trn, ta cng c th tm V0 t dng in khuch tn ca in t vdng in tri ca in t.

0.... =+ inn Enedx

De

Thn volt7,0V

dn

g thng nu ni P-N l Sivolt nu ni P-N l Ge

Vi cc h p cht ca Gallium nh GaAs (Gallium Arsenide), GaP (GalliumPhos

II. DNG IN TRONG NI P-N KHI C PHN

cch:

0

3,0V0

pho), GaAsP (Gallium Arsenide Phospho), V0 thay i t 1,2 volt n 1,8 volt.Thng ngi ta ly tr trung bnh l 1,6 volt.

CC:

Ta c th phn cc ni P-N theo hai



35/163


- Tc dng mt hiu in th gia hai cc ca ni sao cho in th vng P ln hnvng N mt tr s V. Trng h p ny ta ni ni P-N c phn cc thun (ForwardBias).

Nu in th vng N ln hn in th vng P, ta ni ni P-N c phn ccnghch (Reverse Bias).

1. Ni P-N c phn cc thun:

o ra dng inIp. in t khuch tn t vng N sang vng P to ra dng in In. Dng in I qua ni P-

N l

o thi gian v v tr ca tit din A v ta c mttrng thi thng xuyn nh in In v Ip ph thuc vo v tr ca tit din.

Trong vng P xa vng him, l trng tri di tc dng ca in trng to nndng c in t tvng ng vng ny

+ V0 -R I(Gii hn dng

in)

-

- V +Dng in t

N Vng him P

- VS +

V V

P

VB Jnp Jnn

NJpp Jnn

V V0

x1 x x1 x2 x

Hnh 3

Khi cha c phn cc, ngang mi ni ta c mt ro in th V0. Khi phn ccthun bng hiu in th V th ro in th gim mt lng V v trthnh VB = V0-V, do ni P-N mt thng bng. L trng khuch tn t vng P sang vng N t

: np III +=

Dng in I khng ph thuc vng dng

Jpp. Khi cc l trng ny n gn vng him, mt s b ti hp vi cN khuch tn sang. V vng him rt mng v khng c in t nn tro



36/163


cc l trng k ng b mt v tip tc khuch tn sangvng N nhng b mt ln v c s ti hp vi cc in t trong vng ny.

Tng t, s khuch tn ca in t t vng N sang vng P cng tun theo qui chtrn. Ta l cc th nhn m c i xng v tng s cc dng in l trng vdng in t phi bng mt hng s

n 1 nn 2

J = Jpp(x1) + Jnp (x1) = Jpn(x2) + Jnn(x2)

Dng in Jpn l dng khuch tn cc l trng, nn c tr s ti tit din x l:

huch tn thng ngang qua m kh

t tr.

Ta c: Jpp (x1) = Jpn(x2)J ) = J (x )p (x

Dng in J ti mt tit din bt k l hng s. Vy ti x1 hoc x2 ta c:

dx)x(dP.D.e)x(J = nppn

h Pn(x)Trong , Pn(x) l mt l trng trong vng N ti im x. Ta tnTa dng phng trnh lin tc:

A.e

1.

x

IPPP nnn 0t p

p

V dng n Jpn khng ph thuc vo thi gian nn phng trnh trthnh:

=

i

2p

nn2n

2

L PPdxPd0= Trong ppp .DL =

[ ] pLxx

nnnn ePxPPxP

2

00.)()( 2

= V c nghi l:m s

[ ]0

2

n2np

p

xx

np2pn P)x(PL

D.e

dx

dPD.e)x(J ==

=

Suy ra,

p

dpVdv T=Ta chp nhn khi c dng in qua m i ni, ta vn c biu thc: nh trong

tr bng.

Ly tch phn hai v t x1n x2 ta c:

ng hp ni cn

=pp

T

p)x(pp

Vdv )x(pV

0

2n

01

B dp

Ta c:

M: VP

PlogVVVV

0n

0pT0B

==

Suy ra:

=

0n

2nT P

)x(PlogVV



37/163


V

T

0

Vn2n e.P)x(P = Nn:

[ ]0n2pn

Jp

p2 P)x(PL

1.D.e)x( = Do :

D V

L0

p = 1e.P..e)x(J TV

n

p

2pn

Tng t, ta c:

[ ]0p1p

nn1np n)x(nL

1.D.e)x(J =

= 1en.

L

D.e)x(J T

0

V

V

pn

n1np

Suy ra, mt dng in J trong mi ni P-N l:)x(J)x(JJ 1np2pn +=

+= 1e.n.Dp.DeJ

TV

V

pon

noP

LL nPNh vy, dng in qua mi ni P-N l:

+=D

p.D

e.AI noP

1e.n.

LLTV

V

pon nP

t:

DD

=P

P0 .L

.e.AI

Ta

+ pon

nno n.L

p

c:

e0

1TV

V

hng trnh ny i l phng trnh Schockley

=I I

P c g

Trong :n

DDkT nppe

VT =

==

l hng s Boltzman

VT=0,026 volt. Khi mi ni chuyn vn bnhth i t 0,3 V n 0,7 V ty theo mi l Ge hay Si,

Vi K/J10.381,1k 023=

coulomb10.602,1e = , l in tch ca electronT l nhit tuyt i.

19

nhit bnh thng, T=273

0

K,1e10

V

VTV

V

T

>>> ng, V thay

TV

V

Vy, 0

Ghi ch: Cng thc trn chng trong trng hp dng in qua mi ni kh ln(vng c tuyn V-I thng, xem phn sau); vi dng in I tng i nh (vi mA trxung), ngi ta chng minh c dng in qua mi ni l:

e.II



38/163


= 1eII TVV

0

Vi = 1 khi mi ni l Ge = 2 khi mi ni l Si

2. N c phn cc nghch:

i P-N c phn cc nghch, ro in th tng mt lng V. L trng v int khng th khuch tn ngang qua mi ni. Tuy nhin, di tc dng ca nhit, mt s tin t v l u t vng Nsang t nh, thng chngvi c

rong trng hp ni P-N phn cc nghch vi hiuin th V


39/163


40/163


III. NH HNG CA NHIT LN NI P-N:

Thng thng ta thy rng I0 s tng ln gp i khi nhit mi ni tng ln 100C

I Ge Si

V0,3V 0,7V

Vi chc A

n c nghch Phn cc thun

P N P N

- V - V>0 +

I0

Hnh 6

Si Ge

Ph c


41/163


p dng:10

2).C25(I)Ct(I

t00 =

25

00

102

.nA2525100

=

181.nA25=

1( A525,4)C00I 00 =

t c a ni P-N khi phn cc thun cng thay i theo nhit .

t ca ni P-N tng, in th thm a mi n m ( d dn inhn). Ngi ta thv gim 2,02mV dikhi nhit tng ln 10C.

2. Tnh ch

Khi nhi c i gi niy rng, khi nhit tng ln 10C in th thm gim 1,8mV diode Si

ode Ge. Mt cch tng qut c th coi nhin th thm gim 2mV

C/mV2tV 0

D =

. hit c ni P-N cng quyt nh in th sp . Nu nhit tng ln nmt tr no th in th sp s gim xung rt nh v mi ni P-N khng cn sdng c na. Nhit ny l 1500C i vi Si v 850C i vi Ge.

IV. N

i ta thng ch n hai loi ni trca ni P-

1. Ni trtnh: (Static resistance).

Ni tr tnh l in trni ca ni P-N trong mch in mt chiu. Ngi ta nhngha

I(mA) 450C350C250C

0 0,66 0,68 0,7 V

Hnh 8

3 N a

I TRCA NI P-N.

Ng N

in trmt chiu mt im phn cc l t s V/I im .

I (mA)

0 V V(Volt)

Hnh 9

P

N

I Q


V

Rs

Vs

I


42/163


Ni tr a ni ti im Q l:c

IV

RD =

Khi ni P-N phn c khng

c thun cng mnh, dng in I cng ln trong lc in th Vgn nh i nn ni trcng nh.

2. Ni trng ca ni P-N: (Dynamic Resistance)

Gi s dng dng in ngang qua ni P-N l IQ tng ng vi mt in th phncc t

h t lng V t tr s VQ th I cng bin thin mt lng tng

ng I t tr s . T s

hun VQ.

K i V bin thin m

IQ VIb

ng vi d ca tip tuyn ti im Q v uyn ca

ni P-N

c i c t

.

t:dr

= ;r1IV gi l in i P-N khi phn n.

tn hiu u nh, ta c:

dc trng ca n cc thu

V i

Qd dI

dVIV

r =

=

Vi

= 1e.II TVV

0

Suy ra:

~

V

I

w

P

N

Rs

Vs I

I Q

V V

Hnh 10



43/163


= V

V

T0 e.V

1I

dVdI

T

Ngoi ra,

0V

0V

0 Ie.I1e.IITT =

= VV

Hay TVV

00 e.III=+

Do ,T

0

VII

dVdI

+

=

V in trng l:

0IIdV +

Thng thng, 0II >> nn

Td

VdIr

==

I

V

rT

d

= nhit bnh thng (250C), VT = 26mV, in trng l:

)mA(ImV26.

r

= d

Vi dng in I kh l , =1, in trng rd c thc tnh theo cng thc:n

)mA(I

nhit bnh thng, nu I

mV26rd =

hdn P

h c, thng thng khong vi chc .

ng chnh l kiu mu ca Diode vi tn hiu nh ng in trng khi phn cc nghch

Q = 100mA th rd = 0,26. Trong mt ni P-N t c, vc tip tr gia cc mi ni, in tr gia hai vng bn v N nn in trngthc s ln hn nhiu so vi tr s tn

in trni

y c . Ngi ta c nh ngha

=

in tr in trvng N = rb+rd

Hnh 11

rac = rp+rn+rdvng P

rac=rorp rnrd

Qr dI

dVr =



44/163


V dc ca ti p tuyn ti Q khi ni P-N phn cc nghch rt nh nn in trng rrrt ln, hng M.

V. IN DUNG CA NI P-N.

1. in dung chuyn tip (in dung ni)Khi ni P-N c phn cc nghch, vng him c ni rng do c s gia tng in

tch trong vng ny. Vi mt s bin thin V ca hiu in th phn cc nghch, intch trong vng him tng mt lng Q. Vng him c tc dng nh mt tin gi lin dung chuyn tip CT.

dT W

A.VQ

C

=

=

Trong , l hng sin mi ca cht bn dn, A l in tch ca ni P-N v Wdl rng ca vng him.

vng him thay i nn indung chuyn tip CT cng thay i. Ngi ta chng minh c CT c tr s:

Khi in th phn cc nghch thay i, rng ca

( )nR0T

VVC

+=

K

Trong , K l hng s ty thuc vo cht bn dn v k thut ch to. V0 l roin th ca ni P-N (Si l 0,7V v Ge l 0,3V). VR l in th phn cc nghch.

31

n = trong trng hp ni P-N l dc li (linearly graded juntion) v21

n = trong trng

h c ng (brupt juntion).p ni P-N thuc loi d

Nu gi Cj(0) l tr s ca CTo c khi VR=0, ta c:

n

0

R

jT

V

V1

)0(CC

+

=

P - + NVR# VS

N N

- VS +

Ni P-N khi phn cc nghch Dc li Dc ng

Hnh 12

RL P P

-

+

++

++-

--

-



45/163


Trong c thng, CT c tr s t 5pF n 100pF

2. in dung khuch tn. (Difusion capacitance)

Khi ni P-N c phn cc thun, l c khuch tn t vng P sang vng Nv i n t khuch tn t vng N sang vng P. S phn b cc ht ti in thiu shai

bn vng him to nn mt in dung gi l in dung khuch tn CD.. Ngi ta chngminh c in dung khuch tn CDt l vi dng in qua ni P-N theo cng thc:

c ni P-N thng

trng


TD V

IC

=

rong ,TP

PP D

== , l i sng trung bnh ca l trng; = 2 i vi ni P-N l

Si, 1 i vi

hng thng, CD c tr s t 2000pF n 15000pF.

VI. CC LOI DIODE THNG DNG

iode cbn l mt ni P-N. Th nhng, ty theo mt cht tp pha vo cht bndn thun ban u, ty theo s phn c a diode v mt s yu t h a cnhiu loi diode khc nhau v tm ng d ca chng cng khc nha

iode chnh lu:

diode thng dng nht, dng i in xoay chiu thng l in th 50Hzn 60Hz sang in th mt chiu. Diode ny ty loi c th chu ng c dng t vitrm mA n loi cng sut cao c th chu c n vi trm ampere. Diode chnh luch y u l loi Si. Hai c tnh k thut cbn ca Diode chnh lu l dng thun ti av i p ngc ti a (in p sp ). Hai c tnh ny do nh sn xut cho bit.

P

Hnh 13

2L

= ni P-N l Ge.

T

D c c

ngk

u.c na m t

1. D

L

n

Anod CatodA

K K hiuNP N


46/163


47/163


Kiu mu in th ngng (Knee-Voltage model)

Trong kiu mu ny, in th ngang qua diode khi c phn cc thun l mt hngs v c gi l in th ngng VK (khong 0,3V i vi diode Ge v 0,7 volt i vidiode Si).

Nh vy, khi phn cc thun, diode tng ng vi mt diode l tng ni tip

vi n

Kiu mu diode vi in trng:

hi in th phn cc thun vt qu in th ngng VK, dng in qua diode tngnhanh trong lc in th qua hai u diode V cng tng (tuy chm) ch khng phi lhng hi ch n gimth q

gun in th VK, khi phn cc nghch cng tng ng vi mt ngt in h.

KD

s nh kiu mu trn. chnh xc hn, lc ny ngi ta pua hai u in trng r0.

+VS

R

+

VS-

R

+VD = -VS

-

0ID =

VD

ID

0

c tuynV-I

Phn cc nghchHnh 15

-

ID

VDVK+ VK-

ID

VD

+ VK-

0VDVK



48/163


0 iuhnh Q(ID VD) khi n c dng trong mch hnh bn.

+ VD

Th d:

Tc tuyn V-I ca diode 1N917(Si), xc nh in trng r v tm imv

Gii:

Bc 1: dng kiu in th ngng:

mAVV

I KS 77,47,015

' =KR

D 3

=

=

ID -

I

V V0

I

Q

V00 V

D Diode thc D

K D D

D

D0

I

V1

==

doco

V0: in th offset

r

+ VD

ID -

+ VD

Diode l tng

ID - + r0 - + V0 ID

VD= V0+r0IDHnh 18 - 19

4321

65 ID=4,77mA

ID (mA)

QID=4,67mA

Vs=15V

R=3K

+VD=?

-

ID=?

0,2 0,4 0,6 0,8 0,9 V (volt)0 D

Hnh 20

Vs=15V

R=3K

+VD=0-

,7V

ID=?

Hnh 21



49/163


Bc 2: vi ID =4,77mA, ta xc nh c im Q (VD=0,9V)

c 3: v tip tuyn ti Q vi c tuyn tm in th offset V0.V0=0,74V

c 4: Xc nh r t cng thc:

B

B 0

= 16,074,09,0V

== 32r D

c 5: Dng ki u vi in trng r0.

77,477,4DID0

B u m

A00467,0323000

74,015

rR

VVI

0

0SD =+

=

+

=

ID=4,67mA

VD=V0+r0ID=0,74+0,00467x32=0,89V

h :

rong trng hp diode ng vi tn hiu nh, in trng r0 chnh l intrng rd m ta thy ph ng vi in trca hai vng bn v N.

r0=rac=rp+rn+rd=rB+rd

vi rd=

+VS=15V

-

R

+VK=0,74V

-

Hnh 22

r0=32

ID

V

C

T c dn trc c dn P

mAI

mV26

D

V d: Xem mch dng diode 1N917 vi tn hi VS(t)=50 Sint (mV).

m in th VD(t) ngang qua diode, bit rng in trrB ca hai vng bn dn P-N l0.

ii:

u nh

T1

Vs=15V

R=3KVs(t)+ -

+

VD(t)?-Hnh 23

50mV

-50mV

G

Theo v d trc, vi kiu mu in th ngng ta c VD=0,7V v ID=4,77mA.T ta tm c in trni rd:

=== 45,5mA77,4ID

r

mV26mV26rd

Mch tng ng xoay chiu:ac=10 + 0,45=10,45



50/163


in thnh Vdm ngang qua diode l 50.45,15

VR

rV acdm == 300045,15r mac ++

u mu tn hiu rng v hiu ng tn s.

y m t mt diode c dng vi tn hiu hnh sin c bin ln.

Hnh 24

Vdm=0,256 Sint (mV).Vy in th tng cng ngang qua diode l:VD(t) = 700mV + 0,256 Sin t (mV).

VD(t) 0,256mV

t

Ki

Hnh sau

+

-

Vs(t)

+

-

R=3K

700mV

rac Vd(t)

Vs(t)

+

-

+VL(t)

-RL

vS(t)

-30V

30V

Vs(t)

+

-

+RL

--30V

+30V

Bn k dng Diode dn

+30V

-30V

+30V Bn k m

Vs(t)

+

-

+RL

-VL(t)=0

Diode ngng

vS(t)

vL(t)

0

Diode dn

Diode ngng

0

Hnh 25



51/163


Khi diode c dng vi ngun tn hiu xoay chiu tn hiu bin ln, kiu mutn hi

t qu l na chu k dng ca tn h diode dn v xem nh mt ngt inng mch. na chu k m k tip, diode b n cc nghch v c vai tr nh mt ngtin hmch. Tc d g ny ca diode c g i l chnh lu na sng (mch chnh lusc kho st kgio trnh mch in t).

p ng trn chng khi tn s ca ngun xoay chiu VS(t) thp-th d nhin50/60Hz, tc chu k T=20m 6,7ms-khi tn s ca ngun tn hiu ln cao (chu k hng nano giy) th ta phi quan tm n thi gian chuyn tip t bn k dng sang bnk m ca tn hiu.

hi tn s ca tn hiu cao, in th ng ra ngoi bn k dng (khi diode cphn cc thun), bn k m ca tn hiu c c mt phn v c dng nh hnhv. C l tn s ca ngun tn hiu cng cao th thnh phn bn k m xu hin ngra cng ln.

iu ng ny do in dung khuch tn CD ca ni P-N kh ln khi c phn ccthun (CD c tr t 2000pF n 15000pF). Tc dng ca in dung ny lm cho diodekhng th thay i tc thi t trng thi dn sang trng thi ngng dn m phi mt imt thi gia ng c gi l thi gian hi ph u m i kn tcdng ca in dung c

vS(t)

u nh khng th p dng c. v vy, ngi ta dng kiu mu mt chiu tuyntnh.

K iu,ph

n

s/1

Kng qua

h t


vS(t)

vL(t) vL(t)

t(ms)

s)

t(ms)

t(ms)t(m

Hnh 26

H

n (th c, ki u diode pha ni.

rB rd rB rr

CD CT

K K

c Phn ghch

Hnh 27

A A

Phn c thun cc n


52/163


53/163


vS(t)T=2tr t

t

id(t)

0

0

2. Diode tch sng.

Cng lm nhim v nh diod

Hnh 29

Tn hiu tns cao

vS(t) T=10trt

t

id(t)

0

0

Tn hiu tns thp

e chnh lu nhng thng vi tn hiu c bin nhv tn s cao. Diode tch sng thng c ch to c dng thun nh v c th l Gehay S

ca diode schottky.

a thy trong diode schottky, th i ta dng nh ay th cht bn dnloi P v cht bn dn loi N l Si. Do nhm l mt kim loi nn ro in th trong diodeschottky gim n ng ca diode schottky khong 0,2V n 0,3V. l diode schott ho ngc ln hn th sp cngnh h n diode Si.

o th i gian hi phc rt nh ( i trng n diode schottky c dngrt ph bin trong k thut s v iu khin.

i nhng diode Ge c dng nhiu hn v in th ngng VKnh.

3. Diode schottky:

Ta thy nh hng ca thi gian hi phc (tc thi gian chuyn mch) ln dngsng ng ra ca mch chnh lu. rt ngn thi gian hi phc. Cc ht ti in phi dichuyn nhanh, vng him phi hp. Ngoi ra, cn phi to iu kin cho s ti hp gial trng v in t d dng v nhanh chng hn. l nguyn tc ca diode schottky.

M hnh sau y cho bit cu to cn bn

P-thnN.Si

Ro in th Schottky

SiO2 NhmAnod Catod

Tip xc Ohm

Anod Catod

Hnh 30

T ng ng m th

h nn in th ngky c in th bo diode Si v in

D thi nhanh) n



54/163


Hnh 31

VD (Volt)

SiDiodeSchottky

Id (mA)

0 0,2 0,4 0,6 0,7

DiodeSchottkySi

ne

Nh kho st ph c, khi in th phn cc nghch ca diode ln, nhnght t in sinh ra di tc nhit bin trng mnh trong vng h ng vn tcv ph vcc ni ho tr trong cht bn dn. Cch ny c chng cht v cng ta cdng in ngc rt ln. Ta ni diode ang trong vng b ph hu theo hin tng

tu h hng ni P-N.

Ta cng c mt loi ph hu khc do s ph hu trc tip cc ni ho tr di tcdng ca in trng. S ph hu ny c tnh hon nghch, ngha l kh ng httc dng th cc n c lp li, ta gi hin tng n r.

Hiu ng ny c ng dng cc diode Zener. Bng cch thay i nng ch t pha, ngi ta c th ch to c cc diode Zener c in th Zener khong vivolt n vi hng trm volt. l khi phn cc thun, c tuyn ca diode Zener ginght d yn c dng ca diode Zener l khi phn

cc ngh

4. Diode n p (diode Ze r):

n tri dng im t

sau

yt v gy

i in tri ho tr y l hiu ng Zene

ch to

iode thng (diode chnh lu). c tu

ch vng Zener, in th ngang qua diode gn nh khng thay i trong khidng in qua n bin thin mt khong rng.



55/163


* nh hng ca nhit :

Khi nhit thay i, cc ht ti in sinh ra cng thay i theo:

Vi cc diode Zener c in th Zener VZ < 5V th khi nhit tng, in th Zener

i l diode tuyt -diodeavalanche) li c h s nhit dng (VZ tng khi nhit tng).

5V gn nh VZ khng thay i theo nhit.

Kiu mu l t

rong kiu mu l tng, diode Zener ch d n in khi in th phn cc nghch lnhay b ng in th VZ. in th ngang qua diode Zener khng thay i v bng in th

gim. Vi cc diode c in th Zener VZ>5V (cn c g

Vi cc diode Zener c VZ nm xung quanh

* ng ca diode Zener:

T

ID (mA) + VD -

IDVng phn cc nghch

VD (Volt)

VK=0,7V

Vng phn c thunc

I=-ID=IZ

V=-VD=VZ- +

erVZ=Vzen0

Hnh 32

Hnh 33

-4 -3 -2 -1 0

-5-10-15-20-25-30-35-40-45

VD(Volt)ID (mA)

-40 -30 -20 -10 0

-5-10-15-20-25-30-35-40-45

VD(Volt)A)ID (m

250 600C 600C 250C

) Diode c VZ5V(a

C



56/163


VZ th VZ, diode Zener khng dnin (ID=0).

4,3V dng diode zener 1N749 nh sau:

hi cha mc ti vo, th d ngun VS=15V, th dng qua zener l

. Khi in th phn cc nghch nh hn hay bng in

+ V -Z

Do tnh cht trn, diode zener thng c dng ch to in th chun.

Th d: mch tao in th chun

Hnh 34

IZV =-V

K :

mA8,22470

3,415

R

VVI ZS =

=

=

hc t, trong vng zener, khi dng in qua diode tng, in th qua zener cngtng cht t ch khng phi cnh nh kiu mu l tng.

gi ta nh ngh in trng c a diode l:

* Kiu mu ca diode zeneri vi in trng:

T

N a

ZT

in th in th ngang qua hai

ZOZTZ I

VVZr

==

ron : VZO l nghch bt u dng in tng.VZT l u diode dng in s dng IZT.

T g

VS=615VX Ti

R=470

IN749 I4,3V

Hnh 35

VS=615VX Ti

R=470

+ IVZ=4,3V

-

D Z

ID=-IZDiode l tng

ID

0 VD

-VZ

+ V -Z



57/163


5. Diode bin dung: (Varicap Varacto

Phn trn ta thy, s phn bin tch dng v m trong vng him thay ikhi n th phn cc nghch th ia ha diode mt in dung:

r diode)

i ay i, to ra g i u

dWV

in dung chuyn tip C

T

AQC =

=

t ng dng ca diode l dng n n t tin thay i. Th d nh mun thayi t cng hng ca mt mch, ngi ta thay i in th phn cc nghch ca mt

diode bin dung.

Hnh 36

T t l nghch vi rng ca vng him, tc t l nghchvi in th phn cc.

c tnh trn c ng dng ch to diode bin dung m tr sin dung s thay

i theo in th phn cc nghch nn cn c gi l VVC diode (voltage-variablecapacitance diode). in dung ny c th thay i t 5pF n 100pF khi in th phncc nghch thay i t 3 n 25V.

M h mn s

+ VZ -

IZ

ZZ + VZ0 -

Diode l tng

IZT

0

IZ

VZVZ0 VZT

6040

20

C(pF)

80

VR(Volt)0 -2 -4 -6 -8 -10 -12 -14

c tuyn ca in dung theoin th c dng nh sau:

Hnh 37



58/163


6. Diode hm (Tunnel diode)

c ch to ln u tin vo nm 1958 bi Leo-Esaki nn cn c gi l diodeEsaki. y l mt loi diode i nhiu loi diode khc. Diodehm c nng pha cht ngoi lai l t nhiu (c vng P ln vng

N)

ng nh sau:

Khi phn cc nghch, dng in tng theo in th. Khi phn cc thun, in th p, dng in tng theo in th nhng khi ln n nh A (VP IP), dng in li t

ng gim trong khi in th tng. S bin thin nghch ny n thung lng B (VV IV).au , dng in tng theo in th nh diode thng c cng cht bn dn cu to. cnh c th ca diode hm ty thuc vo cht bn dn cu to Ge, Si, GaAs (galium

senic), GaSb (galium Atimonic) Vng AB l vng in trm (thay i t khong0 n 500 mV). Diode c dng trong vng in trm ny. V tp cht cao nn vngim ca diode hm qu h p (thng khong 1/100 ln rng vng him ca diodeng), nn cc ht ti in c th xuyn qua mi ni theo hin tng chui hm nn

T s Ip/Iv rt quan trng trong ng. T s ny khong 10:1 i vi Ge v 20:1i vi GaAs.

Mch tng ng ca diode hm trong vng in trm nh sau:

c bit c dng khc vn hn diode thng r

c tuyn V-I c d

thSt

A5hth

c gi l diode hm.

ng d

LL

CiR

U Diodebin dung

Hnh 38

I(mA)

V(volt)

Anod Catod

IP

IV

VP 0,25 0,5V

B Thung lng

nh A

Diode thng

Diode hm

0

Hnh 39



59/163


Ls: Biu thin cm ca diode, c tr s t 1nH n 12nH.RD: in trchung ca vng P v N.CD: in dung khuch tn ca vng him.

Th d, diode hm Ge 1N2939: Ls=6nH, CD=5pF,Rd=-152, RD=1,5

Diode c vng him hp nn thi gian hi phc nh, dng tt tn s cao. Nhcim ca diode hm l vng in trm phi tuyn, vng in trm li in th thpnn kh dng vi in th cao, nng cht pha cao nn mun gim nh phi ch tomng manh. Do , diode hm dn dn b diode schottky thay th.

ng dng thng dng ca diode hm l lm mch dao ng tn s cao.

Bi tp cui chng

1. Dng kiu mu l tng v in th ngng ca diode tnh dng in I1, I2, ID2 trong

mch in sau:

2. Tnh dng in I1 v V in th ngng cadiode)

VO

D /Si

2D /Si

R1=1K

-12V

R2=3K

+12V

1

I

I2

RDLs

Cd

-Rd

Hnh 40

O trong mch sau (dng kiu mu l tng v

I1 I2

ID21

R1=1K

R2=350D /Si

10V

D /Ge2



60/163


ng mch in sau khi R2 = 50 v khi R2 = 200. Cho bit Zener s dng

Z = 8V.

3. Tnh IZ, VO troc VZ = 6V.

100

4. Tnh I, VO trong mch sau, cho bit Zener c V

IZ R212V

+20VR1=1K

IR2=3K



61/163


Chng V

TRANSISTOR LNG CC

I. CU TO CBN CA BJT

m 1947bi hai nh bc hc W.H.Britain v J.Braden, c c o trn cng mt mu bn dnGerm nium hay Silicium

nh sau y m t cu trc ca hai loi transistor lng cc PNP v NPN.

a nh vng pht E c pha m (n i lai nhiu), vngnn B c pha t v vng thu C li c pha t hn na. Vng nn c kch thc rt hp

(nh nht trong 3 vng bn dn), k n l vng pht v vng thu l vng rng nht.Transistor NPN c p ng tn istor PNP. Phn sau tp trung kho sttrn transistor NPN nhng i vi transistor PNP, cc c tnh cng tng t.

II. TRANSISTORTRNG THI CHA PHN CC.

t rng khi pha cht cho (donor) vo thanh bn dn tinh khit, ta c cht bndn loi N. Cc in t t do (cn tha c t cho) c mc nng lng trung bnh gn di dn in (mc nng lng Ferm nng ln). Tng t, nu cht pha l chtnhn (acceptor), ta c cht bn dn loi P. Cc l trng ca cht nhn c mc nng lng

trung bnh nm gn di ho tr hn (mc nng lng Fermi gim xung).

(BIPOLAR JUNCTION TRANSISTOR-BJT)

Transistor lng cc gm c hai mi P-N ni tip nhau, c pht minh nh t

a .

H

Cc phtE

Emitter

B Cc nn (Base)

n+ p n-Cc thu

CCollecter

E C

B

Transistor PNP

CcE

Emitter

B Cc nn (Base)

nCc th

CCollec

p-u

ter

E C

B

Transistor NPN

Hnh 1

phtp+

T n thy rng, ng cht ngo

s cao tt hn trans

Ta bia ch

i c



62/163


Khi ni P-N c xc lp, mt ro in th sc to ra ti ni. Cc in t t dtrong vng N s khuch tn sang vng P v ngc li, cc l trng trong vng P khuchtn sang v

o

ng N. Kt qu l ti hai bn mi ni, bn vng N l cc ion dng, bn vngP l cc ion m. Chng

ca transistor. Quan st vng him, tathy r

to ra ro in th.

Hin tng ny cng c thy ti hai ning kch thc ca vng him l mt hm s theo nng cht pha. N rng

vng cht pha nh v hp vng cht pha m.

Hnh sau y m t vng him trong transistor NPN, s tng quan gia mc nnglng Fermi, di dn in, di ho tr trong 3 vng, pht nn, thu ca transistor.

n+Vng pht

pVng nn

n-Vng thu

Mc Fermi tng cao

Vng him

M ermi gim Mc

n+ Vng pht p Vng nn n- Vng thu

Di dn in

Di ho tr

E(eV)

c F Fermi tng nh

Di dn in (Conductance band)

Mc Fermi xp thng

Di ho tr (valence band)

Hnh 2



63/163


64/163


Dng IB r (hng microat nh mpere) nn ta c th coi nh: IE # IC

IV. CC CCH RP TRANSISTOR V LI DNGI

Khi s dng, transistorc rp theo mt trong 3 cch cn bn sau:

p theo kiu cc thu chung (3)

c chung chnh l cc c ni mass v dng chung cho chai ng vo v ng ra.

p, ngi ta nh ngha li dng in mt chiu nh sau:

N.

Rp theo kiu cc nn chung (1) Rp theo kiu cc pht chung (2) R

I

Trong 3 cch rp trn, c

Trong mi cch r

vaongoienDong

rangoienDong enng = idolio

li dng in ca transistor thng c dng l li trong cch rp cc phtchung v cc nn chung. li dng in trong cch rp cc pht chung c cho bi:

E IC

vo ra

Kiu cc nn chung

IEIB

vo ra

Kiu cc thu chung

IBIC

vora

Kiu cc pht chung

Hnh 4



65/163


B

CDCFE I

Ih =

Nh v

li dng in trong cch rp cc nn chung c cho bi: li dng in trong cch rp cc nn chung c cho bi:

y: IC = DC.IBy: IC = DC.IBNhng: IE = IC + IB = DC.IB+IB

IE = (DC + 1).IB

Nhng: IE = IC + IB = DC.IB+IB IE = (DC + 1).IB

E

CDCFB I

Ih =

c tr s tDC vi chc n vi trm, thm ch c th ln n hng ngn. DC c trt 0, n 0,999 tu theo loi transistor. Hai thng sDC v DCc nh sn xutcho bit.

phng trnh cn bn:

IE = IC + IBTa c: IC = IE IBChia hai v

95

T

c cho IC, ta c:

B

C

E

CC

B

C

E

I

I1

I

I1

I

I

I

I1 = =

Nh vy:DCDC

111

=

Gii phng trnh ny tm hay , ta c:DC DC

DC

DCDC 1

= vDC

DCDC 1 +

=

* Ghi ch: cc cn c trn l tng qut, ngh l vn stor PNP.

in c chy trong hai transistor PNP v NPN c chiu nh sau:

h d:t transistor NPN, Si c phn cc sau cho IC = 1mA v IB = 10A.

g th a ng vi transi

Ta ch dng th

IE

IC

IE

IB

NPN

ICIB

PNP

Hnh 5

TMTnh DC, IE, DC.

Gii: t phng trnh:

BI

C

DC

I= , Ta c: 100

A10dc phng trnh:

mA1==

T



66/163


IE = c: IE = 1mA + 0,01mA = 1,01mAIC + IB, ta

99,0mA01,1

mA1V t phng trnh:

IEDC

IC= ==

r Si PNP c DC = 50 khi IE = 1,5mA. Xc nh IC.Gii:Mt transisto

9,0DC 850150

1 DC

DC =+

=+

=

IC = DC.IE = 0,98 x 1,5 = 1,47mA

V. D RANSISTOR.

dng in r ngc(bo ho ngh c phn cc nghch.Dng in r u l ICBO, c nh sn xut cho bit, c m t

bng

. Hnh v sau y chodng in ICBO.

NG IN R TRONG T

V ni thu nn hng c phn cc nghch nn cng c mti qua mi ni nh trong trng h p diode t

ch) ngc ny c k hi

hnh v sau:

y l dng in i t cc thu qua cc nn khi cc pht hta thy thnh phn cc dng in chy trong transistor bao gm c

IE = 0

ICBOICBO

VCC

RC

h

Current

Base (

Opene

Collector (cc thu)

(dng in)

Hnh 6

cc nn)

mitter (cc pht h)Cc E

n+ p n-

Hnh 7

IE

IC = DCIE + ICBO

VEE VCC

E C

DCIEICBO

IE

IB

R R



67/163


Nh vy, ta c: IC = DCIE + ICBONu I xp x 0, xem nh khng ng k.

Suy ra, IC = DC(IC + IB) + ICBO

Ta tm thy:

CBO

Ta c: ICDCIE l cng thc l tng m ta thy phn trn. Ngoi ta, t phng trnh

dng in cn bn:

IE = IB + IC

IC = DCIC + DC IB + ICBO

DC

CBOB

DC

DCC 1

II

1I

+

=

Nhng:DC

DCDC 1

= 1

1 DC

DDC +

=1+ C

DCDC

DCDCDC

1

1

11

+=+

hay vo phng trnh trn, ta tm IC = DCIB + (DC + 1)ICBO

gi ta t: ICEO = (DC + 1)ICBO v ph h trn c vit li:IC = DCIB + ICEO

CEO nh l dng in chy t cc C qua cc Eca t cng c nh sn xut cho bit.

c t t nhy t

VI. C TUYN V-I CA TRANSISTO

Ngi ta thng ch n 3 loi c tuyn ca transistor:n ng vo.n ng ra

Mch n

1=

T c:

N ng trn

Nh vy, ta c th hiu dng in r Iransistor khi cc B h. Tr s ca ICEO

C hng sDC, DC, ICBO, ICEO r vi nhi .

R.

c tuy c tuy c tuyn truyn

t g qut xc nh 3 c tuyn trn c biu din bng m hnh sau:

RC

Hnh 8

ICEO

VCC

c nn h

ICEO

Current (dng in)

Emitter (cc pht)

Openbase (cc nn h)

Collector (cc thu

IB = 0

)C

I1 I2BJT

V2V1 Ng ra V22V11 Ng vo

R1 R2



68/163


im cn ch : tu theo loi transistor v cc cch rp m ngun V11, V22 phi mcng cc (sao cho ni thu nn phn ni pht nn phn cc thun). CcAmpe k c volt k V1 v V2 c ng chiu.

Chng ta kho st hai cch mc cn bn:L

1. Mc theo kiu cc nn chung:

Mch sau:

c tuyn ng vo (input curves).

L c tuyn biu din s thay i ca dng in I theo in th ng vo V viVCB

c tuyn c dng nh sau:

hn xt:

cc nghch vng phi mc I1, I2, c

in nh

I1 I2

V2V1VEE

RE RC


E BE

c chn lm thng s.

N

VCC

Hnh 10

IE IC+

VBE VCB

+

+

VCB = 01V

VCB = 00V

V h

+

VCB = 20V

VCB = 10V

CB

0,6 VBE (Volt)0,40,20

IE (mA)

Hnh 11


69/163


Khi ni thu nn h, c tuyn c dng nhc tuyn ca diode khi phn ccthun.

in th ngng (knee voltage) ca c tuyn gim khi VCB tng.c tuyn ng ra (output curves)

L c tuyn biu din s thay i ca dng in cc thu IC theo in th thu nn

VCB i dng in cc pht IE lm thng s.

sau: Ta ch n ba vng hot ng ca transistor.

ng thng song song v cch u. Trong cc ng dngthng thng, transistorc phn cc trong vng tc ng.

ng ngng: ni nn pht phn cc nghch (IE=0), ni thu nn phn cc nghch.Trong vng ny transistor khng hot ng.

Vng bo ho: ni pht nn phn cc thun, ni thu nn phn cc thun. Trong ccng d ng c bit, transistor mi c phn cc trong vng ny.

2. Mc theo kiu cc pht chung.

y l cch mc thng dng nht trong cc ng dng ca transistor. Mch in nh sau:

v

c tuyn c dng nh

Vng tc ng: Ni nn pht phn cc thun, ni thu nn phn cc nghch. Trongvng ny c tuyn l nhng

V

0

1

2

3

4

5

6

2 4 6 8

I = 0mA

1 mA

2 mA

3 mA

A

5 mA

6 mA

VCB (V)

IC (mA)

Vng ngng

ngVng tc

4 m

V

ngboha

Hnh 12

ICBO E



70/163


+ I1I2

V2V1 VCCVBB

RBRC

Hnh 13

IBIC

+

VBE VCB

++

c tuyn ng vo:

iu din s thay i ca dng in IB theo in th ng vo VBE. Trong hiu ththu pht VCE chn lm thng s.

c tuyn nh sau:

c tuyn ng ra:

iu din dng in cc thu IC theo in th ng ra VCE vi dng in ng vo IBc chn lm thng s.

Dng c tuyn nh sau:

B

IB (A)

B

0

VBE (V)

0,2 0,4 0,6 0,8

VCE = 0V

VCE = 10V

VCE = 1V100

40

80

60

20

Hnh 14



71/163


o ho, vng tc ng v

in rICEO.

c tuyn truyn: (Transfer characteristic curve)

T

Linh Kien Dien Tu_DHCT

Documents

Transcript of Linh Kien Dien Tu_DHCT