tieu luan mach dien tu 2

7/31/2019 Tieu Luan Mach Dien Tu 2

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KHOA IN T LP HT4ATLT

BI TIU LUN MN HC: MCH IN T 2 Ti: KHO ST P TUYN TN S CA MCH L

TNG T Gio vin hng dn:

LU TH VINH Sinh vin thc hin:

L NG NGC 10318961V MNH H 10322371L NG TR CU 10305361NGUYN HONG MINH 10305301PHM QUYT THNG 10305811


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I. GII THIU Mch lcl mt b phn rtquan trngtrong k thut

mch in t. Mch lcc tc dngcho tn hiu nmtrongmt di tn s iqua v chncc tn hiutrong di tn s cn li. Do vy, mch lc cdng chn lc tn shayloi b tn s cacc tn hiu in.

Phn loi: Theo chc nng: Thng thp Thng cao Thng di Thng chn di Theo cu to: Mch lc th ng Mch lctch cc


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S mch lcthng thpRC:

p ng tn s ca mch lcthng thpRC:

p ngbin ca mch lcthng thpRC:


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p tuyn tn s ca mch lc thng thp

Tn s ct ca mch lcthng thpRC:

p ng pha c a m ch lc thng th p RC:

Pha caCR j 1

1 chnh l pha c a 1 tr i pha ca 1+j CR .

Ta c = 0 - arctg CR = - arctg CR

tn s thp f 0 nn 0 = - arctg 0 = 0 o

tn s cao f nn = - arctg = - 90 o

tn s ct f = f c , = C th = - arctg 1 = - 45 o


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S mch lcthng thp LC:

p ng bin ca mch lcthng thp LC:

1.2. Mch lcthng cao Mch lcthng cao chcho cc tn hiuc tn scao i qua

mch lc. Cc tn hiuc tn s thp th khng qua c mch lc.

Khiu mch lcthng cao

(HPF : High pass filter)


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S mch lcthng cao RC:

p ng tn s ca mch lcthng cao RC:

p ng bin ca mch lcthng cao:


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Ta c = 0 arctg(-1/ CR )= arctg 1/ CR tn s thp f 0 nn 0 =arctg 1/0 = arctg =

90o

tn s cao f nn =arctg = arctg 0 = 0 o tn s ct f = f c , = C th =arctg 1 = 45 o

Nh vytn hiura b smpha so vitn hiuvo . tn s cao mc smpha nh, tn s thp mc smpha ln hn v tn s ct th mc smpha l 45 o. Trong nhiu trng hp, s smpha ny s lm cho tn hiura bmo dngso

vitn hiuvo


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S mch lcthng cao RL:

p ng bin ca mch lcthng cao RL:

S mch lcthng cao LC:


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p ng bin ca mch lcthng cao LC:

1.3 Mch lcthng di Mch lcthng dicho cc tn hiu nm trong mt

khong tn s no qua c mch lc, cc tn hiuc tn s nmngoi khong tn s th khng qua c mch lc.

K hiu ca mch lcthng di:

Hoc

(BPF: Band pass filter)


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1.4 Mch lc chn di Mch lc chn di ngncc tn hiu nmtrong mt

khong tn sno iqua mch lc, cc tn hiuc tn s nmngoi khong tn s th qua c mch lc.

Khiu ca mch lc chn di:

p tuyn tn s ca mch lc chn di:

c1 t n s ct d i ; fc 2 t n s c t trn


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C 4 loi mchchnh: - Mch lcthng thp.

- Mch lcthng cao. - Mch lcthng di. - Mch lc ct di.

1. Mch lcthng thp (Low pass Filter-LPF)

- Mch lcthng thp cn bn:

Dng mch


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Ngita thng chnRf =R gimdng offset

- Mch lcthng thp -40dB/dec:

Trong nhiu ng dng, ta cn phi gimnhanh li ca mchkhi tn s vtqu tn s ct, c nghal dc ca bng tn phi ln hn na. l mc ch cacc mch lc bccao.


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Dng mch

Nu chnC2=2C1, ta c:


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mchny khuch i s gim i 40dB khi tn s tng ln 10 ln( li gim i100 lnkhi tn s tng ln 10 ln).


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- Mch lcthng thp -60dB/dec:

t c dc hn na-gn vil tng-ngita dng mch lc-20dB/dec mc ni tip vi mch lc-40dB/dec c dc-60dB/dec ( li gim i 60dB khi tn s tng ln 10 ln-gc pha ti tn s ct l -1350).


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Dng mch cn bn nhhnh sau


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http://diavatly.com/media/kunena/attachments/66/11_2012-01-15.JPG


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- Mch lcthng cao 40dB/dec:

Dng mch

Do l mchvoltage follower nn in th 2 uR1 chnh l v0.Ta c:


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- Mch lcthng cao 60dB/dec:

Ngita dng 2 mch40dB/dec v 20dB/dec ni tipnhau t c dc60dB/dec.

ChnC1=C2=C3=C;
http://diavatly.com/media/kunena/attachments/66/14_2012-01-15.JPG


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Vi mchny in th ng ra v 0max t n tr s ti a mt tn sno gil tn s cng hng r. Khi tn skhc vi tn s cng hng, khuch i gim dn. Tn s thp hn r lm li gim i cn 0.707v 0max gil tn s ngt thp L v tn scao hn r lm li gimcn 0.707v 0max gil tn s ngtcao h.Bngthng c nh ngha: B=H - L Khi B0.1r c gil mch lc dithng bng tn rng.


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- Mch lc di thng bng tn hp Dng mch


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Ti tn s cng hng r:


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T phngtrnh (1) ta tm c:
http://diavatly.com/media/kunena/attachments/66/h5.JPG


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tieu luan mach dien tu 2

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