Chương 7 _ Chất bán dẫn và Diode

Trng i Hc Cng Ngh Thng Tin HQG TPHCM

Mn hc: Nhp Mn in T

Tp. HCM - 2012

Cht bn dn v DiodeKhi nim c bn v cht bn dnCht bn dn l g? L nhng cht c c im trung gian gia cht dn in v cht cch in. V phng din ha hc th cht bn dn c 4 in t lp ngoi cng. (Ge) v (Si)

T cc cht bn dn tinh khit ban u, ngi Cht bn dn tinh khit ta to ra hai loi bn dn: bn dn loi N v bn

dn loi P. Sau ghp chng li vi nhau tora cc linh kin transistor hay diode

Cht bn dn v DiodeKhi nim c bn v cht bn dnVng dnCu trc nguyn t ca germanium ; silicon.Wg

Vng cm

Wg

Vng ha trCht cch in

Cht bn dn

Cht dn in

Bn dn pha tp

Cht bn dn v Diode

Cht bn dn loi NKhi ta pha mt lng nh cht c ho tr 5 nh Phospho (P) vo cht bn dn Si thmt nguyn t P lin kt vi 4 nguyn t Si theo lin kt cng ho tr, nguyn t Phospho ch c 4 in t tham gia lin kt v cn d mt in t v tr thnh in t t do => Cht bn dn lc ny tr thnh tha in t ( mang in m) v c gi l bn dn N e e e e e EC EF EFi

Ch : Trong bn dn loi N th nng electron nhiu hn nng l trng. Trong bn dn loi N, electron gi l ht ti a s, cn l trng gi l ht ti thiu s.

h

EV

Phn b mc Fermi ca bn dn loi N

Bn dn pha tp

Cht bn dn v Diode

Cht bn dn loi PNgc li khi ta pha thm mt lng nh cht c ho tr 3 nh Indium (In) hoc Boron (B) vo cht bn dn Si th 1 nguyn t Indium s lin kt vi 4 nguyn t Si theo lin

kt cng ho tr v lin kt b thiu mt in t => tr thnh l trng ( mang in dng) vc gi l cht bn dn P e EC EFi EF EV

Ch : Trong bn dn loi P th nng l trng nhiu hn nng electron.

h

h

h

h

h

Trong bn dn loi P, l trng gi l ht ti a s, cn electron gi l ht ti thiu s.

Phn b mc Fermi ca bn dn loi P

Cht bn dn v DiodeChuyn tip P-NTrc khi tip xcMi khi bn dn trng thi cn bng (tng in tch dng cn bng vi tng in tch m) v nng tp cht trong hai loi bn dn phn b u. EC EF EFi EV Loi N Loi P EC EFi

EF EV

Cht bn dn v DiodeChuyn tip P-NSau khi tip xcDo chnh lch nng (pp>>pn ; nn>>np), sinh ra hin tng khuch tn. L trng khuch tn t P sang N, cn in t (electron) s khuch tn t N sang P dng khuch tn

t P sang N. ng thi, cc ht ti thiu s ca hai bn dn s di chuyn qua lai ln nhau dng tri.

Cht bn dn v DiodeChuyn tip P-NTrng thi cn bng

Chuyn tip P-N

P

N

8

Cht bn dn v DiodeChuyn tip P-NTrng thi cn bngEtx : in trng tip xc

Min ngho

-

+

P

N

Chuyn tip cch in8/2010 9

Cht bn dn v DiodeChuyn tip P-NPhn cc thun Cc dng ni vi cc P cn cc m ni vi cc N (UAK >0) Cc dng ca ngun in p ngoi s y l trng pha bn P di

chuyn sang bn N v ngc li, cc m ca ngun ngoi s y in t bn N di chuyn sang P lm kn mch. Kt qu l trong mch c dng in chy. Dng in ny gi l dng in thun v c gi tr tng theo hm m vi in p ngoi t vo

10

Cht bn dn v DiodeChuyn tip P-NPhn cc thun

P

N

11

Cht bn dn v DiodeChuyn tip P-NPhn cc nghch Cc dng ngun in p ngoi ni vi N cn cc m ni vi P Cc m ngun s ht l trng pha bn P cn cc dng li ht in

t ca bn N. Kt qu l min ngho m rng hn, khng c dng in qua chuyn tip v khng c dng in mch ngoi.

12

Cht bn dn v DiodeChuyn tip P-NPhn cc nghch

P

N

13

Cht bn dn v DiodeDIODE

Cu to v k hiu Nguyn tc lm vic ca diode c tuyn Vn-Ampe ca diode

Phn loi v ng dng

14

Cht bn dn v DiodeDIODECu to v k hiu Diode bn dn l linh kin in t gm 1 chuyn tip P-NA K

Cc ni vi bn dn P gi l cc Catot cn cc ni vi bn dn N gi l

cc anot. K hiu

15

DIODE

Cht bn dn v Diode

Nguyn tc hot ng Diode lm vic da trn tnh cht dn in mt chiu ca chuyn tip P-N. Khi c phn cc thun (UAK > 0): diode dn in, trong mch c dng

in chy qua. Khi ny c th coi diode nh mt kha in t ng (ngn mch) nu UAK > UDUAK > UD

UAK < UD

16

Cht bn dn v DiodeDIODENguyn tc hot ng Diode lm vic da trn tnh cht dn in mt chiu ca chuyn tip P-N. Khi phn cc ngc (UAK < 0): diode khng dn in, trong mch ch c

dng in ngc rt nh chy qua. Khi ny c th coi diode nh mt kha in t m (h mch).

17

Cht bn dn v DiodeDIODEc tuyn V-A:I D(mA)

Phn thun ca c tuyn (UAK > 0) UD : in p ngng ca diode. UD 0,3V (Ge) UD 0,7V (Si) Ithmax l dng in thun cc i cho php ca diode in p ng vi gi tr Ithmax c gi l Ubh, c gi tr 0,8V ( Ge), 1,2V (Si). Vng phn cc thun c c trng l dng ln (mA), in p nh v in tr nhUAK(V)

UBR UD 1V V ng phn cc ngc V ng phn cc thun

Phn ngc ca c tuyn (UAK < 0) Dng ngc bo ha c gi tr rt nh IS c nA Khi UAK = Udt (in p nh thng) th dng in ngc tng vt, gi l hin tng nh thng chuyn tip P - N Udt 12V i vi diode tch sng v khong vi chc V ti 1kV vi diode nn in. 18

Cht bn dn v DiodeDIODEPhn loi

Diode chnh lu Diode n p (Zener) Diode bin dung (Varicap)

Diode pht quang (LED), thu quang (Photo diode) Diode xuyn hm (tunnel), cao tn, xung

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Cht bn dn v DiodeDIODEDiode chnh lu (nn in) K hiu v hnh dng thc t

Cch xc nh cc ca diode: theo k hiu hoc dng Vn k. ng dng Mch chnh lu Mch hn bin Mch dch mc20

Cht bn dn v DiodeDIODEMch chnh lu Mch chnh lu na chu k

Mch chnh lu c chu k

21

Cht bn dn v DiodeDIODEMch hn bin

Mch hn bin trn

Mch hn bin di

22

Cht bn dn v DiodeDIODEDiode Zener Diode Zener c cu to tng i

c bit ch n c nng pha tp cht rt cao, c v bng thy tinh trong sut v kch thc kh nh.

Diode Zener lm vic trn on c tuyn ngc, li dng ch nh thng v in ca chuyn tip P-N n nh in p. Ngha l khi b phn cc ngc v lm vic trong vng nh thng th n khng b hng nh cc diode khc. in p nh thng ca diode Zener thng kh nh (vi chc Vn tr xung) .

23

on c tuyn ngc ca diode Zene6 4 2 0 20 40

V

60

I

80100 120 140

Dng in ngc(mA)

V

in p st trn diode gn nh khng i

Cht bn dn v DiodeDIODEMt s tham s ca diode zener in p n nh UZ in tr trong Ri Cng sut nh mc PZ, n l cng sut tiu tn trn diode khi c dng IZ

chy quaP Z = U Z . IZ Imin l tr s dng in nh nht ti im m hin tng nh thng n nh

Imax l tr s dng in cc i qua diode c xc nh bi cng sut tiu

tn cc i diode (nu I > Imax diode s b chy)

25

Diode bin dung (Varicap)

Gi tr in dung ca diode c tnh bng cng thc: Trong : : hng s in mi ca cht bn dn S: din tch mt ct ngang ca chuyn tip P N dtx: b dy ca chuyn tip P-N

Cv

S d tx

Gi tr ca Cv thng rt nh, khong t 2pF n 100pF. iu chnh gi tr ny ngi ta thay i gi tr ca dtx bng cch iu khin in p ngc t vo diode26

Cht bn dn v DiodeDIODEDiode pht quang (LED)

LED

Khi c phn cc thun s pht ra nh sng

Cht bn dn v DiodeDIODEDiode thu quang (photodiode)

RS

Power supply

VS Photodiode

Photodiode c phn cc ngc v dn in khi c nh sng chiu vo28

Cht bn dn v DiodePhng php o kim tra Diode t ng h thang x 1 , t hai que o vo hai u Diode, nu :

o chiu thun que en vo Ant, que vo Katt => kim ln, o chiu o kim khng ln l => Diode tt Nu o c hai chiu kim ln = 0 => l Diode b chp.

Nu o thun chiu m kim khng ln =>l Diode b t.