VII. MACH TAO XUNG VUONG
Trang khi do, dau vao dao I~ co di¢n lip lang dan len tir av, di¢n ap tang do
tl.1 C n'olp qua R thea quy lu~t ham mil vai cae hang so thai gian T = RC.
Khi tl.) fi<;lP va co Von' < Vin+ thl m<;lch khucch d~i thU11 toan van 6 tr~ng
theE bao hoa duong. Khi tl.1 C n<;tp den mue di9fi ap Vin ' > V,/ thl m~ch
khuech d;:ti thu~t toan d6i thanh tf<;lng th,ii baa hoa am, dau fa co Vo = - Vcr:_ Luc nay, du pha.n ap Rl-R2 dua di¢n ap am ve dau vao thu~n 1,,- voi mue di¢n ap 13.:
(Vi,: < OV)
Trang khi d6, b dau VaG dao In" van con dang b mue di~n ap dUC1ng vai tf! s6 Vill -> + Vee. RJ (R , + R2), do tl.1 C con n~p di¢n. Nhu v~y, khueeh d~i thu~t toan se ehuy~n sang tr~ng thai baa hoa am nhanh, eho qnh xung vuong th~ng dung. TI.1 C bay gio se phong di~n ap duang dang n~p tren tl,l qua di¢n tra R, va teU a dau ra xu6ng mat.
Khi tl,l C phong di¢n lip duong dang co thl VII\+ van b mue di¢n ap am nen khueeh d~i thu~t toan van b tr'!.ng thai baa hoa am. Khi tl.1 C da phong het di¢n ap duang thl se n~p di¢n qua R d~ eo di¢n ap urn dang eo, do diu ra dang b tr~ng thai baa hoa am. Chieu n~p di¢n bay gia nguqe vai ehieu dong
n~p tren.
Khi lI.J C n~p di¢n ap am den mue Vin-< Vi/ (di~n ap dau vao dio nha han di¢n ap dau vao thu~n) thl khueeh d~i thu~t toan l<.ti d6i thanh tr<.tng thai baa hoaduang vadau ra co Vo = +VCco
M~eh tra l'!.i gii thiet ban d<1u vu qua trlnh tren tiep tl.1e dien ra m¢t each tuan hoan.
v v t
t
+Vcc
t
-Vee
Hinh 4.19. D(}I1g di¢n ap tin hi¢u m(}ch dao d¢ng tich thodt
Muc gi6i h<;ln di~n ap dau fa Hi: VOMAX >:::: +Vcc va VOM1N >:::: -Vee. Milc giai h<;ln di¢n ap b hai dau van la:
D<;lng di¢n ap b dau vao dao lin· eo d<;lng tam giac. Thai gian di¢n ap b vao dau vao dolo lin· tang tir VB len V A ia khuech d~i thu~t toan b tr:;tng thai bao hoa
duong, thOi gian di¢n ap dau vao dao lin· giiim tu VA xu6ng VB la khuech d:;ti
thu~t toan b triplg thai bao hoa am. D<p1g di~n ap b dau vao thu~n lin + va dau ra la xung vuong d6i x-ung. Chu ky eua tin hi¢u duqc tjnh theo cong thuc:
T ~ 2RC In R, + 2R,
R,
TflIO'ng hqp d~c bi~t: R, = 2 R, --> T = 2 R. C.ln 2 = 2 .R. C. 0,69 --> f = 1/2.0,69. R. C = 1/1 .4.R. C R, =R,-->T=2R.C.ln3=2.R.C.I,1 --> f = 1/2.2 R. C (In 2 = 0,69) (ln3= 1,1)
Cac m~ch dao d¢ng duqc su dl:Jng lam ca.tZ m~ch t~o ra tin hi¢u song mang trong cac h~ thong thu phat tin hi~u, cac m~ch t~o tin hi~u quet trong cac thiet
bi t~o man sang ...
Cau hoi