1Chng 1: Diode bn dn

2Ni dungGii thiu Vt liu bn dn Diode bn dn thng thng Chnh lu Phn tch mch diodeMch xn (clippers) v mch ghim in p

(Clampers) Diode zener Cc loi diode khc nh hng ca nhit v cc thng s k

thut

3K hiu

Gi tr ti im tnh Q (quiescent-point):IEQ, VCEQGi tr mt chiu: IE, VCEGi tr tc thi: iE, vCEGi tr tc thi ca thnh phn thay i

theo thi gian: ie, vce

4K hiu

iE = IE + ie

5Gii thiu

Diode l mt linh kin in t phi tuynn gin nht.Cc loi diode: diode chn khng, diode

kh, diode chnh lu kim loi, diode bndn, v.v.Diode bn dn:Cu to v tnh chtPhng php phn tch mchng dng

6Vt liu bn dn

Cc loi vt liu bn dn thng dng:Silicon (Si)Germanium (Ge)Gallium Arsenide (GaAs)

7Cu trc nguyn t

8Cu trc tinh th

9Vt liu bn dn Cc mc nng lng

10

S dn in trong cht bn dn

Dng khuch tn (diffusion current): Khi c sthay i mt electron (hole)

Dng chy (drift current): Khi c in trngngoi

11

Bn dn loi p

Doping: L qu trnh a vo cht bndn cc cht khc cn thit.

Bn dn loi pCht a vo: cht nhn (acceptor material). V

d: Boron (III)Cu trc tinh th v s mc nng lng

(xem trang sau)Phn t mng in ch yu: L trng (positive):

p-type material

12

Cu trc tinh th v s mc nng lng

13

Bn dn loi n

Cht a vo: cht cho (donor material).V d: Phosphorus (V).

Cu trc tinh th v s mc nnglng (xem trang sau).

Phn t mang in ch yu: Electron(negative) n-type material

14

Cu trc tinh th v s mc nng lng

15

Diode bn dn thng thng

Cu trc v k hiu

Lp tip xc pn (pn junction)

16

S phn cc ca diode

17

Quan h gia dng in v in p cadiode

Diode l tng

vi > 0: iD > 0 v vD = 0 (Diode ngn mch: shortcircuit)vi < 0: vD < 0 v iD = 0 (Diode h mch: opencircuit)

viri

vD

iD+

_

18

c tuyn Volt Ampere (VA) ca Diode

I0: Dng phn cc nghchbo ho (reversesaturation current), A

q = 1,6E-19 C k = 1,38E-23 J/ 0K: Hng

s Boltzmann T: Nhit tuyt i, 0Km: 1 m 2: Hng s thc

nghim 25 mV, ti nhit

phng (27 0C)

)1()1( TDD

mVv

omkTqv

oD eIeIi

Phn cc thun (vD>0): Khi :

Phn cc nghch (vD< 0): Khi :

TD mVv T

DmVv

oD eIi TD mVv

oD Ii

19

Diode thc t v Xp x tuyn tnh ho tngon (piecewise-linear approximation)

20

Phng php phn tch mch diode

i vi mch tn hiu ln Xem nh diode l tng

i vi mch tn hiu b Xem diode nh mt in tr ng

21

Chnh lu

Chnh lu l qu trnh chuyn i tn hiu xoaychiu (ac) thnh tn hiu mt chiu (dc)Lu : Cc v d trong phn ny s dng ctuyn diode l tng.

Chnh lu bn sng (Half-wave rectification)

vi = Vimcos(ot)

ri vD iD

vLRL

+

_

_+

Ideal diode

Nguon (Source) Tai (Load)

1

9

22

Chnh lu bn k (bn sng)

nh lut Kirchhoff v in p (KVL):

vi > 0: vD = 0 (Diode ngn mch), ,

vi < 0: Diode h mch: ,

Li

DiD Rr

vvi

Li

iD Rr

vi

Li

LiDLL Rr

RviRv 0Di 0 DLL iRv

23

in p trn ti vL(chnh lu bn k)

24

Phn tch tn hiu chnh lu bn sng

Gi tr trung bnhKhai trin Fourier

Lc (filter) tn hiu chnh lu bn k:Mch lc dng lc b cc hi xoay chiu

(harmonics) nhm gi li thnh phn mt chiuca tn hiu vL(t): Lc thng thp (lowpass filter LPF)

Lm

TLdcL

VdttvT

V )(1,

...4cos15

22cos32

cos211)( tttVtv oooLmL

25

Lc tn hiu chnh lu bn sng Cc mch lc thng thp c bn

Gi s dng mch lc (a) vi RC = 100/0 v R >> RL.Bin in p ng ra ca mch lc ti tn s n0 (n1)l:

vi VLn l bin in p ng vo ca mch lc ti tns n0.

R R R

C

L L

C C C

(a) (b) (c)

nV

RCnVV Ln

o

Lnon 1001 2

26

Lc tn hiu chnh lu bn sng

S dng nguyn l chng chp in p ng ra,

gn sng (Ripple factor): Thnh phn DC: Thnh phn gn sng:Gi tr hiu dng (rms) ca thnh phn gn

sng:

gn sng

...4sin3000

12sin300

1sin

20011)( tttVtv oooLmo

Lm

dcLVV

,

...2sin300

1sin

2001

ttVv ooLmr

280

...

)300(1

)200(1

2)(1)( 22

2/12 LmLm

Trrmsr

VVdttvT

v

011.0280

)(,

dcL

rmsr

Vv

27

Chnh lu ton sng (Full waverectification)

Hot ng v in p ra trn ti vL (chnh lu ton sng)

- +

1

2

3

4

1

4

5

6

8

Ri

1

Ri

1

9

D1

D2

vi viRLRLvL

+

_vL

+

_D1

D2D3

D4

28

Phn tch tn hiu chnh lu ton sng

Gi tr trung bnh: Khai trin Fourier:

Lc tn hiu chnh lu ton sngGi s dng mch lc nh phn chnh lu bn

sng, in p ng ra:

Gi tr hiu dng ca thnh phn gn sng:

gn sng

Lm

dcLVV 2

,

...4cos15

42cos342)( ttVtv ooLmL

...4sin1500

12sin300

22)( ttVtv ooLmo

210)(Lm

rmsr

Vv

0024.04201

29

Mch lc (Filtering)

Hot ng T C c np nhanh n gi tr Vmax ca in p v0(t). Khi v0(t) gim, t C phng in qua RL vi quy lut:

Qu trnh tun hon vi tn s chnh lu fp:fp = 2f0 : Chnh lu ton sngfp = f0 : Chnh lu bn sng

vi f0: tn s ca ngun vi.

1

4

5

6

8

D1

D2

C RLvi vo

+

_

CRt

oLeVtv

max)(

30

Phn tch v tnh ton mch lc

Xp x tn hiu ng ra bng dng sngrng ca (sawtooth wave)T C:

in p gn sng hiu dng:

Chng minh: xem TLTK[1] v [2]

LpRVfVC

max

32)( minmax VVv rmsr

31

Mch nhn i in p (Voltage doublingcircuit)

Bn k m ca vS: C1 np in qua D1 n inp VSmax

Bn k dng ca vS: in p chng chp caC1 v vS np in cho C2 qua D2 n in p2VSmax

1 5

4 8

C1

C2D1

D2Mch nhni in pmt bn chuk

32

Mch nhn i in p (cont)

Bn k dng ca vS: C2 np in qua D1 n in pVSmaxTng in p vS v VSmax trn C1 (c np t bnktrc) t ln ti RL thng qua D1

Bn k m ca vS: C1 np in qua D2 n in pVSmaxTng in p vS v VSmax trn C2 (c np t bn ktrc) t ln ti RL thng qua D2

Mch nhni in phai bn chuk

D1 D2

C1C2

1 5

4 8

RL

+ +vS

33

Nhn tn s (Frequency Multiplication)

Mch chnh lu to ra tn hiu (hi harmonics) ti cc tn s: n0.

S dng mch lc thch hp ly ccthnh phn hi cn thit.

34

Phn tch mch diode

Lu : Cc v d trong phn ny s dng ctuyn Diode thc

Mch Diode n gin ng ti mt chiu(DC Load Line)

vi

rivD

RL vL vT

RT vD

iD iD+++

_ _

_Diode hoccc phnt phituyn

Mch tng ngThevenin ca phn tuyntnh

35

Phng php phn tch mch diode

Phng php thPhn t phi tuyn c th hin bng c tuyn VA:Phn cn li (tuyn tnh) c thay th bng mch

tng ng Thevenin: hay:(DCLL)

Tm hiu hot ng (im tnh Q quiescentpoint)

)( DD vfi

TDTD Rivv T

TD

TD R

vv

Ri 1

36

Phng php phn tch mch (cont)

in p tng ng Thevenin vT thay i (Vd: vT = VTmsint)

37

Phn tch tn hiu nh - in tr ng Tn hiu nh

Thnh phn thay i (ac) ca tn hiu l rt nh so vithnh phn dc.

vi Vim

38

Phn tch tn hiu nh Chuyn trc to v Q: ,

Tn hiu nh: xem ab l on thng i qua Q vc phng trnh:

in tr ng (dynamic resistance):

DQDd Iii DQDd Vvv

d

dd

r

vi

QDD

d iv

r

39

Tnh gi tr in tr ng T phng trnh: , gi tr in tr ng:

vi: IDQ: Dng in tnh im qua Diode Mch tng ng

Mch (a): Tm im tnh Q (IDQ v VDQ), s dng phng php th

Mch (b): Tm p ng tn hiu nh (id v vd), s dng in trng v cc nh lut Kirchhoff

Dng nguyn l xp chng tm tng p ng

T

DmVv

oD eIi

DQDQT

QDD

QDD

d ImVm

ImV

iv

iv

r)(25

(a) (b)

Vdc

RT RTrd

vi

VDQ

IDQ

+ _

id

40

Mch in c thnh phn in khng Reactive elements (L,C) V d:

Gi s: 1/C

41

ng ti xoay chiu ACLL Xt v d trn

gi s: 1/C

42

Phn tch th

Phn tch tn hiu ln - s mo dng v dch chuynim tnh (xem TLTK[1])

Phn tch tuyn tnh ho tng on v mch tngng (xem TLTK[1])

43

Mch xn v mch ghim in pMch xn dng loi b in p nm di hay

trn mt mc chun (reference level)V d 1: (gi s diode l tng)

V d 2: (gi s diode l tng)

R

vi vo

VB

44

Mch xn v mch ghim in p (cont) V d 3: (gi s diode l tng)

Mch ghim in p (Clampers)Mch ghim in p thc hin vic di chuyn tn hiu(shifting operation) theo trc Y vi dch chuyn phthuc vo dng sng ng vo sao cho tn hiu ng ra lunc ghim (clamped) ti mt gi tr c nhV d: Gi s Diode l tng, RC >> T v Vm > VB

Rvi vo

VB

C

VC = Vm -VB

R

vi voVB1 VB2

45

Diode Zener Diode Zener: Hot ng ch yu trong vng phn cc

nghch K hiu v c tuyn VAPhn cc thun: nh Diode thng thngPhn cc nghch: , vZ = VZ = constantminmax ZZZ IiI

VZ: in p Zener IZmax: Dng phn cc nghch

ti a ca Diode Zener IZmin: Dng phn cc nghch

ti thiu vZ = VZ, thngIZmin = 0.1IZmax

PZmax = VZ IZmax: Cng sutti a tiu tn trn DiodeZener

46

Mch n p dng diode Zener

Mc ch: Thit k mch sao cho Diode Zener hot ngtrong vng n p (vng gy breakdown region): IZmax iZ IZmin , vZ = VZ

Phn tch:

IZmax iZ IZmin vi mi gi tr ca vS v iL: min(iZ) IZmin v max(iZ) IZmaxv

vS

Ri

RL

iL

iZ

iR

VZ+

_

vS v iL: khng n nh

LZ

ZS

R

ZSi ii

Vvi

VvR L

i

ZSZ iR

Vvi

minmaxmin)min( ZL

i

ZSZ IIR

VVi maxmin

max)max( ZLi

ZSZ IIR

VVi

47

Mch n p dng diode Zener (cont)

Vi yu cu v ngun (vS) v ti (iL) cho trc, chnc Ri cn phi c

, thng chn IZmin = 0.1 IZmax

Chn Diode Zener :v: v:Thit k: Lm theo th t ngc li xc nh IZmaxca Diode Zener v Ri

maxmin

max

minmax

min

ZL

ZSi

ZL

ZSII

VVRIIVV

maxmin

max

minmax

min

ZL

ZS

ZL

ZSII

VVIIVV

maxmin

minminmaxmaxmax 1.09.0

)()(SZS

ZSLZSLZ VVV

VVIVVII

maxmax LZ II minmaxminmaxmin 101.0 LZLZZ IIIII

48

Thit k mch diode Zener v d 1 Thit k mch n p dng Diode Zener: VZ = 10 V vS : 14 20 V v iL: 100 200 mA

v vChn IZmax = 0.533A Ri = 15.8 Cn xt n cng sut tiu tn cc i trn Ri v DiodeZener:Trn Ri: PRimax = (VSmax VZ)2 / Ri = 6.33 WTrn Diode Zener: PDiode = IzmaxVZ = 5.33 W

vS : 10.2 14 V v iL: 20 200 mA

Khng thit k c !!!

AVVV

VVIVVIISZS

ZSLZSLZ 533.01.09.0

)()(maxmin

minminmaxmaxmax

AII LZ 2.0maxmax AII LZ 110 minmax

AVVV

VVIVVIISZS

ZSLZSLZ 41.09.0

)()(maxmin

minminmaxmaxmax

49

Thit k mch diode Zener V d 2

VZ = 7.2 V; vS = Vdc = 12 V; iL: 12 100 mA; TmRiVSmax = VSmin = Vdc = 12V

v v

Chn IZmax = 100 mA 43.5 Ri 40: Chn Ri = 43.5Cng sut tiu tn cc i:Trn Ri: PRimax = (Vdc VZ)2/ Ri = 0.53WTrn Diode Zener: PDiode = IzmaxVZ = 0.72 W

mAVVV

VVIVVIISZS

ZSLZSLZ 8.971.09.0

)()(maxmin

minminmaxmaxmax

mAII LZ 100maxmax mAII LZ 12010 minmax

50

Diode Zener thc t

Diode Zener thc t (xem TLTK[1])c tuyn VA

Dng phng php th phn tch mch

51

thay i in p (percent regulation) V d: xt v d 1a) trong phn trc. Gi s Izmin=

0.1IZmax = 0.053ADiode Zener thc t c gi tr in tr ng: rd = 2Mch tng ng:

in p ra: Vomax = 10 + 0.532 = 11.1VVomin = 10 + 0.0532 = 10.1V

thay i in p:%Reg = (Vomax Vomin) / V0 danh nh (nominal)%Reg = (11.1 10.1) / 10 = 10%

Ri

rd

iL

vo

+

_

VZiZ

DiodeZener ltng

52

Cc loi diode khc

53

nh hng ca nhit nh hng ln c tuyn VA

in p ngng V (turn-on voltage)

k = 2.5 mV/ oC Dng phn cc ngc I0

K = 0.07 / 0C Quan h gia cng sut v nhit Diode nh lut Ohm

21: in tr nhit (thermal resistance) gia 2 v 1 (0C / W)P: Cng sut tiu tn (power dissipation) ti 2 (W)

)()()( 11 oo TTkTVTVV

)(12

12)()( TTKoo eTITI

PTT 2112

54

nh hng ca nhit (cont)

ng suy gim cng sut (Derating Curve)

TcPj

Tj

Ta

jc

ca

Tj Tjmax: Cho trc bi nh sn xutjc: Hng s, cho trc bi nh sn xutca: C th thay i c, s dng tn nhit (heat sink), nu gim ca

Gim Tj vi cng cng sut Pj (Ta = constant)

55

Thng s k thut

Diode thng thngin p ngc cc i (PIV Peak Inverse

Voltage)Dng phn cc ngc cc i ti PIVin p phn cc thun cc iGi tr trung bnh ca chnh lu bn sngNhit cc i ti tip gip pn Tjmaxng suy gim cng sut

Diode Zener (xem TLTK[1])