- Xanh da trai, xanh la, den, nhO vang.
u' 2m +U3m 2 +U 11m 2 M=
Di~n ap tin hi~u a dtlu va~ m~ch khucch d<;ti thuemg bien d6i tu gia tfi nha nhat U1/hmin den gia tri I6n nhat U1/hmax' Ty so giUa gia tf~ 100 nhat va gia tf~ nha nhat cua di~n ap ella tin hi~u a dau vao cua b(> khuech d<;ti g9i Dili d(>ng cila tin hieu Dlh.
D1/h = U1/hmax/ U1/hmin
Muon khueeh d<;ti tin hi~u nha nhat ciing nhu tin hi~u 100 nhat rna kh6ng co sai l~eh qua mue thl dili d(>ng eua m~eh khuech d~i phai bang ho~c Ian han dai dQng cua tin hi9U. Trong twang hqp dicu ki9n trcn day kh6ng thoa man thi phii thu h9P dui bien thien cua tin hi9U l'!.i.
* Cdc IO{li mh' tmng I11gch khue'eil d~li.
Trong m~lCh khuech d<).i la g~p hai lo~i mea trn hi~u.
+ Mea phi filye/J: La lo~i meo lam cho hlnh dc:~ng tin hi¢u ra sai l~ch so vai dc:)ng tin hic;u vao. Nguyen nhan ehu yeu gay meo la do tinh chat phi tuyen eua cae phfin tit tich clJc nhu tranzito, IC gay ra.
- Trong meo phi tuyen neu tfn hi~u vao Ia hlnh sin thl tin hi¢u ra kh6ng gilr duqc dC).ng hlnh sin nua do ngoai thanh ph an tan so ca ban (0 co bien dQ U! con c6 them die thanh phan tan s6 nco vai dc bien dQ wang ling la U nm.
H~ s6 meo phi tuyen do dng khuyeeh d,-~i g,ly ra duqe bi€u thi bang eong thuc:
u' 2m +U3m 2 +U11m 2 M= M=
Vim
M - 010 biet ti l~ cae song hai (tan s6 nco) chiem bao nhieu % so vai song ca ban. Trcng cae may chat Im;mg eao M eho phcp 1 - 2%
Treng cae may chat lm;mg trung blnh M cho phep 5 - 7 %
Con trong de m~eh khuech d~i rai co tinh chat ch9n 1ge tan s6 - tai lit khung cQng huang can quan Him t6i meo phi tuyen.
+ Meo tan s6: La lo~i meo gay ra khi tang khueeh d~i khuech d~i kh6ng dong deu cae tin hi~u co litn s6 khac nhau. Dti bi~u thi d~ng meo nay ngubi ta dung khai ni~m ve dap tuyen Hin 56 cua tang khueeh d~i. Dola do thi bi€u dien sl! ph,:! thuQc eua h~ so khueeh d~i thee tan so.
Co lo.p meo nay la de cae phan tl'r L, C eua till, eua m~ch va cae phan tl'r ghep kf sinh gay fa
K
Dap (/lyel! tall so' eua lI1(1ch khlleeJ, dgi
II. cAe PHUONG PHAr D1~U KHI~N TRANSISTOR
1. M~ch dieu khi~n el/e goc chung
C, I, C2 ...-l, .,. / , II IJ , [ R, R, E, E, + ,., + III I' • U"
Hillh 2.2: Sa d(j' m(fch dit!u khiln cl/c go(' chung (Be)
OJ
Hlnh 2.2 la sO do fl1<;lch dieu khi~n ci.!c gac chung (con gqi la qrc ba za chung).
RI HI di~n trb J,nh thien cho tranzilo, no s~t hOt di¢n ap ngu6n Ej baa dam
cho cl!c phat (luang hem cl!c gac khoang 0, 1 ~- a,2y.
R2 Iii di¢n Ira tai (ganh).
Tiep giap phat - gac duQ'c phfln cl!c thu~n, con tiep giap gae - gop phan
cl!c nghich.
C1 va C2 Iii 11,l di¢n n6i t;lng gifra Ul.ng truac va tang sau.
Tin hi¢u van dua toi giua hai cl!c phat - gae. Tin hi¢u Hfy fa giiia hai eve goc
- g6p. C1!C goc chung cho ca ffi<;l.ch vao va m~ch fa la gQi lil m~ch cl!c gac chung. Tiep giap goe phut duQ'c pharr cl!c thu~n, nen co dong phat mOl chieu di tir qrc duang ngu6n E I tai qrc phat, roi sang cl!c goc va chia lam hai: m¢t phanla dong gac rat nho di vc cl!c am cua ngu6n El , con phan chu yeu Ia dong gop se vuqt sang cl!c g6p roi ve cl!c am nguon E2. (adsbygoogle = window.adsbygoogle || []).push({});
Dong phit Ie lit dong djnh thien cho m~ch gac chung. Dong phat ph6i hqp voi dong gop 1.: ho~c di~n ap g6p - phat UL-e xac djnh ehe d¢ lam vi~e eua tranzito.
Dua m¢t tin hi~u xoay chieu rai dau van cua m~ch. Trang fllh chu ky duang
cua tin hi~u dng v6i nguon Ell lam cho tiep giap phit - goc phlln egc thu<'!.n
brmg di¢n ap Ian han, dong philt lang len, lam cho dong g6p tang, sl,lt ap tren R2 tang, di~n ap gop Uc' giiim, ughl<1 la duang Jen, nen tin hi~u fa duang len.
Den nlla chu ky am ella tin hi¢u vao, di~n up am cUa tin hi¢u Htm giam di¢n
ap duang cila nguon E, lam cho Uc hOt duang hem so vai egc g6c, ncn Uhc giam lam cho dong cl!c phat Ie giam di, dong C\!C g6p I~ giam thea. SI,II <l.p tren R2
gicim, di~n up gop U" lang len. nghia l~l am han. Do d6 tin hi~u fa am han.
Nhu vi.ly trang m~ch ClyC goe, di~n ap fa dong pha v6i di¢n ap vao.DL!a van
tfnh toan, nguoi ra dIng tfoh duqc tra khang vaa, tra khang fa, h¢ s6 khuech dqi
dbng di~n, h~ ~6 khuech d<,ti di~n ap va h~ s6 khucch d~i cong suat cua tranzito.
Tra khang vao Z" cua m<.lch g6c chung c6 tri s6 khoang (30 -;- 300),0, Zv bien ddi thco z~, ( tra khang ganh - hay tra khang cua m<}ch tai a diiu ra cua m<;lch khuech c1i..li LIng veri nhfrng gia trj dong C\!C g6p Ie nhM djnh thea do thj hinh 2.3a.
Tra khang ra Zm co gia tr~ khoang tu lOOK den 1 M'o, Zr" bien doi thea Z nguon u'ng v6i moi giu lr[ dbng gop nhrit d,nh thea do thi hlnh 2.3b
H~ s6 khucch d<:li dong, di¢n lrong mc..lch C\!C gac chung ia ti so gifra d¢ tang
dona 0 0 oor tren do tan a dona phit: . I:.> I:.> J