Tim hiu PSpicePSpice la mt phn mm dung chay m phong cac s mach in. Trc ht Ban hay ve mt mach in vi cac ky hiu ly trong cac th vin cua PSpice, sau khi t xong cac tri s cho cac thanh phn linh kin cua s mach, Ban se cho chay trinh PSpice khao sat:1.iu kin phn cc cua mach. y PSpice se tinhin ap trn cac ng mach, tinh racng dong in chay vao chay ra trn cac chn cua cac linh kinva tinhcng sut tn hao trn cac thanh phn linh kincua mach2.Cho thy cac mc ap hay dong inbin itrn mach theo truc thi gian, khi Ban cho kich thich mach vi cac dang ngun tin hiu co bin thay i.3.Cho thy ap ngbin cua mach theo truc tn s, khi Ban cho kich thich mach vi cac dang ngun co tn s thay i.Sau y la mt thi du c ban: Khao sat hoat ng cua mt tng khuch ai n gian.Cng vic se gm co cac bc sau:Bc 1: Ve s mach in vi trinh Capture CIS.Trc ht hay kich chut m trinh Capture CIS cua OrCAD dung ve cac mach in nguyn ly. Sau khi ly cac ky hiu co trong cac th vin cua PSpice, chung ta ve xong mt s mach in nh hinh sau:

y la mach khuch ai dung mt transistor, vi in tr R1 cp ap phn cc cho chn B, in tr R2 dung inh mc ap cho chn C va cung la in tr ly tin hiu ra trn chn C, trn chn E chung ta t in tr R3 inh dong va ly tin hiu hi tip nghich sa meo.Khi ve hinh nay, tt ca cac ky hiu Ban uphai ly trong cac th vincua PSpice, vi chi trong cac th vin nay, cac ky hiu linh kin mi co lit k cac thngs dung cho cng vic thit k mach. Khi chay PSpice, trinh m phong se ly cac thng s nay tinh ra cac kt qua. Vy nu Ban ly ky hiu trong cac th vin khac, hay ky hiu do Ban t tao ra, no vn chi la mt hinh vema thi, luc o trinhPSpice se bao li.Bc 2: Lin thng vi trinh PSpiceSau khi a ve xong mt s mach in hp l trn trang ve cua Capture CIS cua OrCAD, Ban se cho lin thng vi trinh PSpice dung phn mm nay thit k, tinh toan cac thng s vn hanh cua mach. Qua cac kt qua Ban co th bit c trang thai lam vic cua mach, t o chon tip qua cac bc khac. Thao tac vi trinh PSpice c thc hin trn thanh cng cu nh cac hinh sau:(1) Kich vao tiu hinh nay lin thng vi trinh PSpice

Ban kich vao tiu hinh nay se bung ra mt ca s, y ban se t tn tuy y PSpice lu gi cac kt qua phn tich vao tn nay.(2) t tn ct gi cac kt qua phn tich.

Trong Name: Ban t tn tuy chon, thi du nh: da-hai-nang-ap, t tn xong nhn nut Create la xong(3) Kich vao tiu hinh nay chon kiu phn tich

Trinh PSpice hay tt ca cac phn mm m phong khacthng chi lam co 4 cng vic chinh, o la:1. Tinh toan trang thai phn cctinh cho mach. 2. Khao sat mach hay c tinh cua cac linh kin vi chc nng quet DC. 3. Khaosatbin cua mach theo truc thi gian t 4. Khao sat bin cua mach theo truc tn s f(4)Chon kiu phn tich la Bias Point, xac lp trang thai phn cc tinh

Trong ca s nay Ban chon kiu phn tich mach: 1. Chon Bias Point tinh toan trang thai phn cc cho mach. 2. Chon DC Sweep dung khao sat mach bng ky thut quet 3. Chon Time Domain dung xem bin thayi theo truc thi gian t 4. Chon AC Sweep dung xem bin thay i theo truc tn s fThng thngkhi thit k mt machin, Ban nn lam theotrinh t sau:* u tin ve cac thanh phn linh kin cua mach co lin quan n iu kin phn cc cua mach, trong phn cc DC cac tu in xem nh lam h mach cac cun dy xem nh lam ngn mach, luc tim phn cc DC, Ban khng cn chu y n vai tro cua cac tu in va cac cun cam.* Tip theo Ban cho chay PSpice vi kiu chon la Bias Point, kt qua phn tich, Ban se co mc ap trn cac ng mach, cng dong in chay qua cac linh kin va cng sut tn hao trn cac linh kin cua mach in. Nu iu kin phn cc cha ung, Ban sa i, nh cho thay i tri s cua in tr, thay i kiu mach...cho n khi ly c phn cc mi chuyn qua cac bc khac.* Khi a ly ung iu kinphn cc ri, Ban ly ngun tin hiu cho kich thich mach va xem cac bin i trn mach theo truc thi gian, luc nay Ban chon kiu phn tich la Time Domain.* Khi mach a lam vic tt vi ngun tin hiu ma Ban a vao kich thich mach, by gi Ban chuyn qua khao sat mach vi ngun tin hiu ma tn s cua no thay i khao sat mach lam vic trong mt day tn rng, Ban chon kiu phn tich la AC Sweep.(5) Cho chay PSpice phn tich mach

Sau khi a khai bao xong kiu phn tich, Ban kich vao tiu hinh nay,xem hinh trn, chay trinh PSpice. Numi vic u binh thng, hp l Ban se co kt qua con nunhmach co dinh li thi trinh PSpice se cho hin ra mtvn bannoi ro mach ang bi li gi, luc o Ban se sa li va cho phn tich lai.Bc 3: Xem kt qua va hiu chinh iu kin phn cc. bit mc ap co trn cac ng mach, Ban kich vao tiu hinh co ch V.

Kt qua phn tich cua PSpice cho thy, vi mc ap ngun nui la 9V DC, mc ap trn chn C la khoang 4V, nm khoang gia mc ngun nui la c, mc ap trn chn B la 0.77V la c, vi rao ap cua mi ni B-E a la 0.6V. Nu Ban mun giam mc ap trn chn C xung mt chut, Ban co th tng tri cua R2, hay giam tri cua R1. y vai tro cua R3 it co anh hng n trang thai phn cc cua mach.Chuyn qua xem cng dong in chay vao ra trn cac chn cua cac linh kin

Kt qua phn tich cho thy, dong chay ra trn chn B la khoang 3uA va dong chay ra trn chn C cua transistor la 489uA, va dong chay vao trn chn E la tng cua hai dong nay cng lai. Nu mun bit h s khuch ai dong tinh cua transistor, Ban ly dong ICchia cho dong IB. Vi mach khuch ai lam vic vi bin tinh hiu nho, dong lam vic ICcua transistor ly khoang na mili-amp la c. Dong ICly ln li ln nhng mc ting n cung ln, ly dong ICnho, mach hoat ng rt m, it nhiu nnhng cho li nho.

Kt qua phn tich trn cho thy cng sut tn hao trn cac linh kin. T cac con s nay, chung ta se bit cach chon cng sut chiu nong cho cac linh kin. Mach cho thy, chung ta dung cac in tr co cng sut chiu nong khoang 1/8 Watt la qua u ri.Bc 4: Khao sat mach vi ngun tin hiu dang Sin co tn s c inh.Sau khi ly ung phn cc, chung ta chuyn qua khao sat mach trang thai ng, ly cac dang ngun tin hiu cho kich thich mach nga vao ri xem s bin i cua cac thng s trong mach.Bc u Ban vao kho ly ngun VSIN va cho ni tin hiu dang Sin nay vao chn B cua transistor qua tu lin lac C1, tu C1 bt cu cho tin hiu i qua ma khng lam sai phn cc hin co trn chn B cua transistor.Ban kich m ca s chon kiu phn tich va khai bao cac thng s phn tich:

*Vi ngun tin hiu Sin co tn s la 1KHz, chu ky tin hiu se la 1ms, Ban chon Run to time la 4ms nu Ban mun xem 4 chu ky tin hiu hin trn man hinh, Ban chon 10ms nu Ban mun cho hin 10 chu ky tin hiu trn man hinh.* Start saving data afterchon 0, co nghia Ban mun xem kt qua t vi tri khi u, nu Ban chon 1ms, trinh PSpice se bo qua phn 1ms khng cho hin ra trn thi bin-thi.* Maximun Step Size chon 0.01ms, y Ban mun trong 1ms PSpice se tinh 100 im, vy vi khai bao 4ms bn trn, trinh PSpice se tinh 400 im cho ve ra thi bin-thi. Khai bao nay qua it hinh ve ra se th, khai bao nay qua nhiu, vt kha nng phn tich cua PSpice, PSpice se bao li.

Sau khi phn tich xong, trinh PSpice cho hin kt qua trn thi bin-thi. T thi nay Ban bit gi:* Ban thy tin hiu vao trn chn B va ly ra trn chn C co tinh ao pha. Khi mc volt trn chn B tng ln thi mc volt trn chn C se giam xung va ngc lai.* Tin hiu nga vao la dang Sin, tin hiu nga ra cung dang Sin, mach khuch ai khng lam meo tin hiu.* Ban ly bin tin hiu nga ra chia cho bin tin hiu nga vao se tinh c li cua mach khuch ai. Mach khuch ai nay cho li gn 40 ln. thy ro hn mt ln na ti dan vao y hinh tin hiu nga vao va nga ra.

y la mach khuch ai lam vic vi tin hiu bin nho. Vy nu chung ta a bin tin hiu ln vao thi se xy ra chuyn gi?

Chung ta tng bin tin hiu t 10mV ln 200mV. Ban xem hinh, trong khai bao ngun: Voffset la 0V, tn s lam vicFreq la 1KHz va bin tin hiu Vamp la 200mV.

Kt qua phntich cho thy,bin tin hiu nga ra a bi meo nng. Phn trn va phn di u bi "ct ngon". Nguyn do la mc volt nga ra khi tng ln khng th vt cao hn mc ngun nui (luc nay transistor trang thai ngng dn)va khi giam xung khng c thp hn mc ap chn B (luc nay transistor trang thai bao hoa).

khao sat tin hiu chung ta co th chuyn qua dung thi ph tn, dung phn tich Fourier, chung ta thy mt tin hiu thun Sin se chi hin mt vach trn thi ph tn, vi cac tin hiu phi Sin, phn tichchui Fourier se cho thy no la s kt hp cua nhiu thanh phn tin hiu Sin co tn s la bi cua tn s c ban, luc o trn thi ph tn ngoai mt vach chinh con xut hin nhiuvach phu khac, chung ta noi o la cac song haicua tin hiu phi Sin. Vy mt tin hiu thun Sin se khng co hai, mt tin hiu phi Sin, nh song vung se phat sinh nhiu song hai. Ngi ta goi tin hiu song vung la song a hai.Bc 5: Khao sat mach vi ngun tin hiu Sin co bin c inh.By gi khao satmach vi ngun tin hiu dang Sin co bin khng i vi tn s thay i. Chung ta vaokho ly ngun tin hiu VAC, cho mc ngun la 1V d phn tich thi. Ban xem hinh.

Cho m ca s chon kiu phn tich: Ban chon muc AC Sweep va khai bao cac thng s phn tich.

Trong Start Frequency ly 10, co nghia la khi u dung ngun tin hiu 10Hz. End Frequency chon 1 Meg, tn s phn tich cao nht la 1MHz. Trong Points/Decade chon 101, nghia la trong mt bc 10, chung ta yu cu PSpice tinh 101 im. Bc 10 la t 10Hz n 100Hz, t 100Hz n 1KHz...Sau khi chay trinh PSpice, chung at co kt qua hin trn thi bin-tn. ban xem hinh

thicho thy: ng cong nga ra thng u va bin 32. iu nay co nghia la machkhuch ai cho ln 32 ln trong day tn tin hiu t 10Hz n 1MHz.Sau y chung ta th xem nhng thanh phn nao se anh hng n ng cong bin-tn.* Khi u thm tu tao tac dung hi tip nghich, ly tin hiu nga ra trn chn C tra v nga vao trn chn B. Tu C3 co tri la 120pF.

Sau khi chay trinh PSpice vi kiu phn tich AC Sweep, chung ta co kt qua nh hinh sau:

ng cong cho thy, vung tn s thp, tac dung hi tip nghich khng ang k vi tri cua tu C3 nho 120pF, nn ng cong bin tn trong vung nay khng co thay i. Nhng khi tn s cua ngun tng cao thi tac dung hi tip nghich ang k, bin tin hiu vung tn s cao bi giam xung. Do vy chung ta bit nu mun giam bin tin hiu vung tn cao thi dung cac tu nho tao hi tip nghich trn chn C v B.By gi th xem tac dung cua cac tu lin lac co tri s nho.Chung ta dung tu lin lac C1, C2 co tri 1uF

Kt qua phn tich chothy, khi dung cac tulin lac nho, tin hiu vung tn s thp bi giam bin. iu nay d hiu, vi dung khang XCcua cac tu in co sc can dong ln i vi cac tin hiu co tn s thp, no can manh cac tin hiu vao ra mach khuch ai, nnkt qua bin vung tn thp bi giam. Chung ta thng noi, nu dung cac tu lin lac nho se lammt tin hiu vung tn thp.

Th xem vai tro cua cac cun dy trong cac mach khuch ai. Gn cun cam L trn chn C, chung ta c gi?

Chungta bit cun dy co cam khang XLtng theo tn s, tn s cang cao, cam khang cang ln. Kt qua phn tich cho thy: Vi cun dyt trn chn C, bin tin hiu vung tn cao tng manh tao rainh, do o cun dy nay quen goi la peak coil.

Qua phn thi pham trn, ti nghi Ban cung a quen vi cach dung PSpice phn tich cac s mach in. Khng cn bit mach in cua Ban n gian hay phc tap trinh t phn tich cung thng gm co cac bc nh phn trinh bay trn. y cung noi ro hn, OrCAD hay PSpice khng dung cho cac Ban khng phai dn chuyn nganh, trc ht Ban phai la dn in t, co trinh trung cp, bit phn tich kt qua qua cac dang thi, bit lam mt s phep toan s cp, nu co trinh toan cao cp cang tt. Nhng theo ti, nu Ban a"m" mn in t ri thi trc sau gi Ban cung phai lam quen vi phn mm nay, vi no giup cho chung ta rt rt nhiu.By gi chung ta vao ung tai cua bai vit:Dung dao ng a hai tao xung dung cun cam L tao mach nng ap DC.Dao ng a hai la gi?Dao ngla chi loai mach in, khi c cp ngun no t phat ra tin hiu.a haila y noi chung ta co tin hiu dang phi Sin, nh song tam giac, song nhon, song vung..., loai tin hiu nay co nhiu song hai (co th xem cac song hai trn thi ph tn cua PSpice). Vy, cac mach in t tao ra tin hiu dang phi Sin quen goi la mach dao ng a hai.Trong bai nay chung ta dung 2 transistor rap thanh mach dao ng a hai tao ra tin hiu dang xung vung, cac tin hiu ly ra trn cac chn C.

Nguyn ly lam vic cua mach nh sau: Binh thng ca 2 transistor u cho phn cc trang thai bao hoa, khi bi kich thich, tng transistor se ln lt tam chuyn vao trang thai ngng dn, va khi transistor t ngng dn tr lai bao hoa thi lai y transistor kia vao trang thai ngng dn. Chi tit Ban co th tim oc lai cac bai vit trc cua ti.

Ban click chut vao dong nay m xemSau khi dung PSpice phn tich mach, chung ta co kt qua nh hinh sau:

Khi mcap trn chn B bi ghim mc 0.7V thi transistor thi ky bao hoa, luc nay mc ap trnchn C xung thp va khi chn B bi tu C y xung mc volt rt m thi transistor bi y vao ngng dn, mc ap trn chn C tng ln bng mc ngun, nhng do phai ch tu nap nn mc ap trn chn C ln khng thng,, iu nay lam cho doc ln khng thng. Luc nay tu C trn chn B se xa in, hinh ve cho thy ng cong xa in, va khi tu C xa ht in chuyn qua nap in, khi ln n 0.7V thi bi mi n B-E ghim ap va transistor lai chuynvao trang thai bao hoa...S nap xa cua 2 tu in se ln lt lam cho 2 transistor ln lt ngngdn ri bao hoa va chung ta co xung vung trn 2 chn C cua 2 transistor.Khi dung xung kich thich caccun cam L phat ra in ap ng chung tacn co xung vi b ln va b xung phai thng. Vy co cach sa doc ln cua xungnay khng?Sa doc ln cua mt xung vungQua phn tich, chungta bit khi transistor Q2 chuyn vao ngng dn, mc ap trn chn C cua Q2 se phai tng ln bng mc ngun, nhng do tu C2 phai nap lai in nn khin cho doc ln cua xung khng thng, vy tranh anh hng cua tu C2 nap in lam cho doc ln khng thng, chung ta cho tu C2 nap lai in qua R5 va cach ly mc ap trn chnC vi tu C2 qua diode D1, iu nay se lam cho doc ln rt thng. Chung ta thy kt qua qua thi bin-thi cua PSpice.Kt qua phn tich cua PSpice cho thy chung ta dung mach R5, D1 a tao c doc lnc cai thin, doc ln rt thng.

Dung cun cam nng apChung ta bit khi dung xung vungcho kich thich cun dy L, qua trinh se co 2 giai oan:(1)Giai oan bm dong vao cun dy, luc nay cun dy L se tao ra dong in ng co chiu chng lai dong in chay vao cun dy. Chung ta noi y la giai oan nap in nng vao cun dy. Cun dy se cha in nng di dang mt t trng.(2)Giai oan xa in, khi ct dong nap vao cun dy L, lng in nng tich cha trong cun dy L sehoan tra lai mach in di dang xung ng, do bin mc xung ng tuy thuc vao thi gian ngt mach dt, thi gian ngt mach dt cang ngn, cang nhanh thi bin xung ng se rt cao. Chung ta dung c tinh nay cua cun dy L tao mc volt cao chomach nng ap.Trong mach, chung ta dung xung ra trn chn C cua Q2, qua R6, ong m transistor Q3. y transistor Q3 lam vic nh mt khoa in ong m nhanh.* Khi Q3 bao hoa, no se bm dong vao cun cam L1. Luc nay cun dy L thi ky nap in nng. Mc volt trn chn C cua Q3 xung gn bng 0V.* Khi Q3 ngng dn, no ct nhanh dong chay qua cun dy L, cun dy se chuyn qua thi kyhoan train nng, no phat ra in ap ng bin caotrn chn C cua Q3. Bincua xung nay se cng thm vi mc ap Vcc cua ngun nui, qua diode D2 cho nap in vao tu loc C3,trn tu C3 chung ta se ly c mc ap DC cao. Trong mach chung ta dung in tr tai R7 lam tai, vi R7 chung ta se at c s cn bng in nng cua mach. hiu c mach lam vic ra sao, chung ta dung PSpice phn tich mach, kt qua phn tich nh hinh sau: thi trn cho thy, trong thi gian 1ms u tin, in ap trn tu C3 c cho nap dong, mc ap trn tu C3 tng ln n 110V, sau o bin giam dn xung do s xa in qua in tr tai R7 va mc ap nga ra se n inh do s cn bng gia qui trinh nap va xa.Co cachnao tao ra mtmc ap DC n inh trn tu C3khng? Mc ap nay it phu thuc vao in tr tai? Chung ta se xet n vn nay trong mach ksau y.Dung hi tip xac inh in ap nga ra.Trong mach chung ta dung ng hi tip vi diode Zener va transistor Q4 cho tt xung theo mc ap nga ra, mach lam vic nh sau:

Khi mc ap trn tu C3 cha ln u cao thi diode zener D3 khng dn in, transistorQ4 con ngng dn, va mach phat xung ong mcp cho Q3 vn hoat ng. Khi mc ap trn tu C3 ln cao hn mc 30V thi diode zener D3 se dn in va no lam baohoa Q4, Q4 bao hoa se lam tt mach dao ng vangng cp xung ong m cho Q3, vy tu C3 tam thi khng c bm in na. Nhng khi mcap trn tu C3 giam xung do cp dong cho tai, luc nay mc ap xung di mc 30V thi diode zener lai vao trang thai tt, khng dn in nava transistor Q4lai ngng dn va machdao ng se chay lai va lai cp in cho tu C3. Vicach hoat ng nh vy, chung ta thy mc ap trn tu C3 se c gi n inh mc 30V. Ban xem thi cua PSpice se thy,mc ap trn tu C3 qua c ch luc nap luc xa ac gi n inh mc 30V.

Mt mach in tng t:Rap mach nng ap dung ic 555 va cuncam L.Noi n dao ng a hai, mach tao ra tin hiu dang xung vung, chung ta nghi ngay n ic inh thi 555. Trong phn nay ti se rap mach nng ap dung ic 555 lam mach tao xung ong m, va cho nng ap vi cun cam L t trn chn C cua mt transistor ong m nhanh va sau cung cho n ap vi mach hi tip iu khincho tac ng vao chn 4, chn resetcua IC 555. Toan b u cho chay m phong vi trinh PSpicetim kt lun.1. Chay m phong PSpice trn mach dao ng vi ic 555.

Mach dung ic555 rap thanh mach daong tao xung. Tn sxung ly theo tri cua R9, R10 va tu C5. Xung ra trn chn s 3 co b ln va b xung rt tt. hiu nguyn ly vn hanh cua mach dao ng vi ic 555, Ban tim xem lai cac bai trc, ti a co trinh bay vn nay chi tit hn.Ban click chut vao dong nay m xemKt qua phn tich cho thy:* Khi mc volt trn chn 2,6 giam xung n mc 1/3 mc ap ngun thi nga ra trn chn 3 bc nhanh ln mc ap cao, luc nay chn 7 h masse va tao iu kin cho tu C5 nap in, dong nap qua in tr R9, R10, va mc ap trn chn 2,6 ang tng dn ln.* Khi mc ap trn chn 2, 6 tng ln n mc 2/3 mc ap ngun thi nga ra trn chn 3 se giam nhanh xung mc ap thp 0V, luc nay chn 7 cho ni masse va tu C5 chuyn qua giai oan xa in, dong xa qua R10va mc ap trn chn 2/ 6 ang giam dn xung....Qui trinh trn se lp i lp lai va trn chn s 3 chung ta se co xung vung vi doc ln xung rt thng va trn chn 2, 6 chung ta co tin hiu dang rng ca, Ban xem thi.

T thi trn, chung ta co th noi cbin cua tin hiu, chu ky cua tin hiu va tinh ratn s cua tin hiuva noi cdang song cua tin hiu. Trong thc tin, Ban phai dung n may hin songmi co ththy c cac tin hiu trn mach in2. Dung cun cam L tao ra xung ng bin cao nng ap

Trong mach nay chungta dung xung vung ra trn chn 3 cua ic 555lam xung ong m transistor Q3. Va cung giai thich tngt nh cac mach in trn, mi khi transistor Q3 dn in no bm in nng vao cun cam L1 va mi khi Q3 ngng dn, t cun cam L1se "bung ra" xung ng co bin rt cao, chung ta cho nn xung nay vi diode D2 va cho nap in vaotu n ap C3, luc nay trn tu C3 se co mc ap DC cao. Trong mach nay mc ap nga ra se t cn bng theo iu kin tai R7.Sau khi chay trinh PSpice chung ta co kt qua nh thi sau: Ban thy mc ap nga ra t cn bng mc khoang 42V, va mc ap nay se thay i theo tri cua in tr tai.

3. Dung mach hi tip n inh mc ap DC trn nga raCu hoi:Co cach nao inh c trc c mc ap nga ra khng? Va tao ra mc ap n inh it bi anh hng theo tri s cua in tr tai?Cu tra li: Co.Chung ta se dung mach hi tip, cho tac ng vao chn s 4 cua ic 555 gi cho in ap nga ra trn tu C3 ly theo tri Vz cua diode zener. Nguyn ly iu khin nh sau:

* Khi mc ap DC trn tu C3 con thp hn mc ap Vz=30V cua diode zener thi D3 khng dn in, vy Q4 tt va chn 4 cua ic 555 cho mc ap cao va ic 555 se dao ng lin tucphat ra xung ong m mach, cun dy L se lin tuc bm in nng vao tu C3, mc volt DC trn tu C3 tng ln cao.* Khi mc ap DC trn tu C3 ln cao qua mc ap 30V thi diode zener D3 se dn in, no lam cho Q4 bao hoa, chn 4 cua ic 555 se bi t mc 0V, luc nay ic 555 se tam tt dao ng, cun dy L ngng bm in nng vao tuc C3.* Do tu C3 lin tuc xa dong qua in tr tai, nn mc ap DC trn tu C3 se giam dn xung, khi mc ap trn tu C3 giam xung di mc 30V thi diode zener lai ngng dn va Q4 lai tt, chn 4 cua ic 555 lai cho ln mc ap cao va ic 555 lai dao ng tr lai, va nh vy cun dy L1 lai cho bm in nng vao tu C3.Qui trinh trn lp i lp lai va gi cho mc ap DC nga ra trn tu C3 c ninh va inh trc theo mc ap Vz cua diode zener.Dung PSpice cho phn tich mach trn, chung ta thy ng biu din xem trn chn 3 cua ic 555 a noi ln ung nguyn ly hoat ng cua mach, ung theo nhng gi chung ta a bit.

Nhin vao ng biu din ly trn chn s 3 cua ic 555, Ban co th noi c din tin cua mach theo truc thi gian t, noi mt cach inh lng va chinh xac, o chinh la cai "tuyt di" cua trinh PSpice. Vi vy dn in t nha ngh rt thich dung PSpice tim hiu cac mach in la, trc khi co y inh bo tin bo cng ra mua cac linh kin v lp rap cac loai mach in nay.Tam ktTi khngmun vit gi hn na, s bai vit se qua dai, chi mong Ban oc hiu cac phn trn va hay tim cach c thu cho c trinh PSpice noi ring hay trinh OrCAD noi chung, va dung phn mm chuyn nghip cao nay cho cng vic nghin cu in t hang ngay cua Ban. Khi co dip ti se tr lai tai nay vi hng m rng hn, bao la hn. Mong Ban thng xuyn vao xem va gii thiu trang web nha phuclanshop.com cho nhiu Ban khac cung vao xem.Va nu co trich dn cac bai vit trang web mim phi nay,Ban nn ghi thm dong ch cho bit xut x cua bai Vit. Chao thn ai!Khi qut v OrCAD 9.2Capture CIS lin thng vi PSpiceSau khi ci xong OrCAD 9.2, trn a cng ca my, Bn c th mc ORCAD, trong th mc ny s c cc th mc con, nh: CAPTURE, LAYOUT-PLUS, PSPICE.

Cc th mc con ca OrCAD 9.2 trn a cngVo CAPTURE, Bn s thy c cc th mc con khc na, nh hnh sau:

Trong cc thmcny hy ch v tm hiu k th mc th vin LIBRARY ca Capture. Trong th mc ny cha cc tp tin th vin ca nhiu k hiu m sau ny Bn s thng xuyn phi dng n.

Khi Bn nhp chut phmStarts thy c mc: ORCAD release 9.2 trong ca s. Cho chut ch ngay mc ny s hin ra mt ca s nh hnh sau: Lc ny Bn mun m trnh no th nhp chut ngay trn tiu hnh ca trnh .Bn cng c thko dicc tiu hnh t ca s ny ra mn n Desktop sau ny c th nhp chut trn cc tiu hnh ny, m nhanh phn mm Bn mun s dng. Th d: Tiu hnh dng m nhanh trnh Capture CIS v cc s mch in nguyn l. Tiu hnh dng m nhanh trnh Layout Plus v bng mch in.By gi thnhp p chuttrn tiu hnh ca trnh Capture CIS. Bn thy m ra vng lm vic ca trnh v s mch in nguyn l. Lc ny v mt mch in v cho lin thng vi trnh PSpice. Bn hy chn mcFile, ri chn mc New v chn mc Project... Bn s thy hin ra mt ca s New Project nh sau:

Trong ca s ny, Bn hy g vo tn tp tin (trong Name) v chn th mc ct tp tin ny (trong Location).*Nu mun lin thng vi trnh PSpice thnh dutrong trn th nht (Analog or Mixed).*Nu mun lin thng vi trnh Layout Plus v board mch in thnh dutrong trn th hai (PC Board).*Nu mun lin thng vi trnh PLD dng np ch?ng trnh vo cc IC PAL, GALTh nh dutrong trn th ba (Programmable Logic).*V nu ch mun v cc s mch in thi, Bnnh dutrong trn th t (Schematic).Sau khi chn xong phn mm lin thng vi mch in v trong Capture CIS. Bn nhn phm OK. Lc ny trnh Capture CIS m ra mt ca s Create PSpice Project, Bn hy chn mc Create a blank Project trnh Capture m ra mt trang v trng.

nh du trong trnCreate a blank project m trang v trng.

Sau khi nhn phmOK, Bn vo vng lm vic chnh ca Capture CIS.

Trong vng lm vic ny, Bn hy dng cc lnhPlace t cc thnh phn ca mt mch in ln bng v. y, Bn c th dng chut sp xp li bng tiu hnh cng c. bng tiu hnh ny, mi tiu hnh ng vi mt chc nng c th.

ly cc k hiu t cc th vin t vo trang v, Bn chn tiu hnh sau:nhp con tr trn tiu hnh PlacePart).Lc ny Bn thy hin ra mt giao din: Trong giao din ny, mcLibrariescho thy cc tp tin th vin hin dng. Part, Bn g vo tn k hiu m Bn mun ly (Th d: g vo 555), Bn s thy hin ra cc nhm t c s 555. T y Bn hy chn k hiu m Bn mun ly. (Th d: 555B), ngay khi c chn, trong khung trng di s cho hin ra k hiu m Bn mun chn (chc nng Preview). Nu ng Bn nhn phm OK. K hiu Bn ly s dnh vo con tr, Bn tm ni t k hiu. t mt k hiu ln trang v, nhn chut tri. Bn c th nhn tip chut tri t k hiu ny cc v tr khc trn trang v.

Bn chn IC 555B c trong th vin ANL-MISC.OLB, k hiu ny hin ra trong khung Preview, nu y ng l linh kin m Bn mun ly, Bn nhn phmOK xc nhn).

Sau khi t xong cc k hiu ln trang v, Bn s thy trn vng lm vic ca Capture CIS c hnh nh sau (xem hnh). Bn chn mcEditv chn mcPart chuyn qua trang v ph (Edit Part), y Bn c th sp xp li v tr cho cc chn ca IC 555 sao cho hnh v r rng, d hiu hn. Chng ti dng chut ko cc chn ca IC 555 to ra mt k hiu mi ca IC 555 nh hnh sau:

Tm hiu IC 555: IC ny c 8 chn, cng dng ca mi chn nh sau:Chn s 1(GND): Cho ni masse ly dng cp cho IC, dng in t s t masse chy vo IC.Chn s 2(TRIGGER): Ng vo ca mttng so p 2. y mc p chun bng (1/3)Vcc, ly trn cu chia Volt to bi 3 in tr 5K. Khi mc p trn chn 2 xung n mc (1/3)Vcc th chn 3 s chuyn ln mc p cao, lc ny kha in trn chn s 7 trng thi h.Chn s 3(OUTPUT): Ng ra, tn hiu ng ra c dng xung (mc p khng thp th cao). Khi chn 2 xung thp hn mc p chun (1/3)Vcc th chn 3 ln mc p cao v khi chn 6 ln cao hn mc p chun (2/3)Vcc th chn 3 xung mc p thp.Chn s 4(RESET): Chn hinguyn, chn Reset xc lp trng thi ng ra. Khi chn s 4 cho ni masse (t mc p thp) th chn 3 b cht mc p thp, ch khi chn 4 t mc p cao th ng ra mi c t do, in p trn chn 3 mi c th lc ln cao lc xung thp, to ra tn hiu dng xung.Chn s 5(CONTROL VOLTAGE): Chn khin, qua chn ny lm thay i cc mc p chun trn cu chia Volt. Khi mc p chun cp cho cc tng so p 1 v 2 b thay i th tn s tn hiu cng thay i theo. Ngi ta thng a in p tn hiu vo chn 5 thc hin s iu ch tn s.Chn s 6(THRESHOLD): Ng vo ca mttng so p 1. C mc p chun bng (2/3)Vcc, ly trn cu chia Volt to bi 3 in tr 5K. Khi mc p trn chn 6 ln n mc (2/3)Vcc th chn 3 chuyn xung mc p thp, lc ny kha in trn chn s 7 trng thi ng kn.Chn s 7(DISCHARGE): Chn x in, chn ny l ng ra ca mt kha in ng m theo p, kha in ny ng m theo mc p trn chn s 3. Khi chn s 3 mc p cao th kha in ng li v cho dng chy ra, khi chn 3 mc p thp th kha in h v ct dng chy ra trn chn s 7.Chn s 8(Vcc): Chn ngun, ni vo ngun nui Vcc cp in cho IC 555. IC 555 c th lm vic vi mc ngun nui t 3V n 18V.n y Bn hy vo kho linh kin vi lnh Place Part (g phm p m nhanh th vin v vo kho chn ly cc k hiu theo s mch in m Bn mun v).* ly cc in tr, Bn gi ra bng tn R (C trong th vin Analog.olb).* ly cc t in, Bn gi ra bng tn C (C trong th vin Analog.olb).* ly ngun nui, Bn gi ra bng tn VDC (Trong th vin Source.olb).Sau khi tt c cc k hiu ca cc linh kin t xong trn trang v. Bn hy dng n lnhPlace Wire cho ni ng mch qua cc chn ca tt c linh kin.Tiu hnh chn dng lnh ni mch. Bn cng c th chn nhanh lnh ny bng cch g phm k t W (Wire). mode ni mch, du con tr c dng hnh ch thp (+). Bn cho con tr chm vo cc chn ca mt k hiu, r chut, dy ni s ko theo qua cc chn khc, khi dy ni chm vo chn linh kin s xut hin mt chm trn (du hiu ca im ni). Bn nhn phm chut tri kt thc mt ?ng ni, nhn phm Esc thi lnh ni mch.Bn hy chn k hiu ni masse, bng cch g phm k t G (Ground) hay nhp chut trn tiu hnh sau:Tiu hnh dng ly k hiu masse cho ni vo s mch in.Sau khi ni xong cc ?ng masse, Bn nhp p chut trn tr s ca tng k hiu linh kin v son li cc tr s ny, lm xong chng ta s c s mch in nh sau:Hnh cho thy ton phn mt s mch in nm trn trang v ca Capture CIS. ly R1, R2, R3, chng ta c th g phm tt P(M lnh Place Part) m kho linh kin v g tn linh kin l R, chn v tr t k hiu ny trn trang v. ly t C1, C2, chng ta c th g phm tt P (Place Part) m kho linh kin v g tn linh kin l C, chn v tr t k hiu ny trn trang v. ly ngun nui V1 chng ta c th g phm tt P m kho linh kin v g tn linh kin l VDC. ly IC 555, chng ta c th g phm tt P m kho linh kin v g tn linh kin l 555. ly du ni masse, chng ta c th g phm tt G ri chn k hiu masse.n y hy hon chnh mch in bng cch bin son tr s cho cc linh kin trn s mch in . ghi tr s cho cc linh kin trn s , nhp p chut trn mt tr s, Bn s thy hin ra giao din Display Properties nh hnh sau:

Trong Value: g vo tr s ca linh kin.Trong mc Display Format. Nu Bn chn mc Value Only th ch c tr s cho hin ra thi, nu chn mc Do Not Display th tr s linh kin s khng hin ra.Son xong nhn phm OK. ghi cc cu ch thch ch Vit ln bn v, Bn g phm T (m lnh Place Text), v trong ca s Place Text, Bn g vo cc cu ch thch ch Vit thuyt minh s mch in.

Sau khi chn xong cc tr s ca cc linh kin trong mch, ghi cc cu ch thch vo mch, Bn s thy s mch in hon chnh nh hnh sau:Ghi ch: c th sp xp tr s ca cc linh kin trn trang v cc v tr bt k Bn nn chn mode tt tnh dnh l?i. Hy nhp chut trn tiu hnh sau.Tiu hnh dng tt m tnh dnh l?i ca cc thnh phn ca mch in trn l?i ca trang v.n y, Bn hon tt cng vic m t mt s mch in trn trang v ca trnh Capture CIS.Hy th lin thng vi trnh PSpice phn tch s mch in trnTrn y l mt mch dao ng dng IC 555, vi cc mch dao ng Bn phi t vo mchiu kin khi u(lnh IC: Initial Condition). Hy g phm P (gi lnh Place Part) m ca s Place Part v chn th vin Special ri chn tn linh kin l IC1, Bn s ly ra ?c k hiu dng qui ?nh iu kin khi u theo ch ?nh trong IC1. Bn hy nhp p chut trn ch IC= ghi vo mc volt khi u (Th d: cho l 0V). y Bn li dng lnh Place Text (phm tt l T) ghi thm cc vn bn ch thch ln s mch in (Bn xem hnh).

n y l Bn chun b xong mt mch in chy trong phn mm PSpice.Cch m phn mm PSpice phn tch mch in trn.Trn vng lm vic ca Capture CIS, Bn thy c mt thanh cng c nh hnh sau:

Trc ht hy nhp chut tiu hnh New Simulation Profile m trang phn tch mch. Bn thy hin ra ca s New Simulation nh hnh sau:

G vo Name tn ca trang phn tch. (tn ty chn).Th d: g vo pt-555 (t tn ty chn, sao cho d nh l ?c).t tn xong, nhn phm Create m ca s chn kiu dng phn tch. Bn thy hin ra giao din c nhiu th chn nh hnh sau:

Trong giao din ny th Analysis, mc Analysis Type cho thy c 4 cch phn tch chnh. l:Bias Point: dng xc ?nh iu kin phn cc DC ca mt mch in. Tnh ton xong, Bn s c cc mc p DC trn cc ?ng mch v c dng in chy qua cc nhnh ca mch.DC Sweep: dng cch qut thng s DC phn tch cc c tnh ca cc linh kin in t. Nh v cc ?ng cong c tnh ca diode, transistor, scr, triac, cc cng logicKho st mch vi cc mc ngun nui DC khc nhauTime Domain (Transient): dng phn tch cc mc p trn cc im ca mch in ly theo bin thi gian( y trc x ly theo bin thi gian). N c cng dng nh Bn ang dng mt my hin sng nhiu tia xem cc tn hiu trn cc im ni ca mch in.AC Sweep/Noise: dng phn tch cc mc p trn cc ?ng ni ca mch intheo bin tn s v gc pha (trc x ly theo bin tn s hay bin gc pha). N dng v ra ?ng cong p ng bin tn, pha tn ca mch.

Trong th d trn, Bn th chn cch phn tch l Transient (Trc x ly theo bin thi gian). dng phn tch ny Bn ch cn g s vo cc trng (Xem hnh):Trong :Run to time, g vo khong thi gian phn tch (Th d: g vo 4ms th).Trong :Start saving data after, xc ?nh thi im bt u cho hin tn hiu.Trong :Maximum step size, chn ?nh b?c in (Th d: g vo 0.01ms).Ghi ch: nu Bn chn b?c in cng nh, tn hiu in ra s cng nt, hnh cng p nhng tp tin d liu ghi li trn a s ln v thi gian phn tch s ko di hn.Sau khi chn xong, nhn phm OK tr li trang v. y Bn chn tiu hnh cho chy trnh PSpice phn tch mch.Nhp chut trn tiu hnh ny chy PSpice cho phn tch mch.Sau khi phn tch xong Bn s thy kt qu hin ra trong trang th. (Bn xem hnh).

Trong trang th ny, chng ta thy tn hiu ly ra trn chn s 3 ca IC 555 c dng xung vung. Lc ny nu mun xem tn hiu trn im no ca mch in, Bn ch cn t ng d ngay trn im .Th d: Cng lc Bn t ng d trn chn 2, chn 6 v trn chn 3. Chng ta s thy dng tn hiu trn chn 3 l dng xung vung v trn chn 2, 6 l dng tn hiu rng ca, c hai cng hin trn cng mt th.

Bn c th thay i tr s ca cc linh kin trn mch in ri cho phn tch li, Bn s c kt qu khc. y, Bn thay i tr s ca t C1, ly tr s ca t nh hn l 0.0047F. Sau khi phn tch li, Bn s thy kt qu hin ra nh sau: (Tn s ca tn hiu tng ln).

Tm li, trong OrCAD 9.2 Bn c th m t mt mch in vi rt nhiu loi linh kin khc nhau, mch c th ?n gin hay phc tp, mch c th cho kt hp cc linh kin loi Analog hay cc linh kin loi Digital. Sau khi phn tch xong. Bn xem kt qu trn cc trang th, qua cc kt qu ny Bn s bit ?c nhng c tnh ca mch in. Thao tc thc hnh gm cc b?c sau:Bc 1: M trang v ca trnh Capture CIS, v cc s mch in hon chnh trong trang v ny.*Dng lnh Place Part vo kho ly ra cc k hiu t ln bn v.*Dng lnh Place Wire ko cc ?ng ni qua cc chn ca linh kin.*Dng lnh Place Ground t ?ng masse ln s mch in.*M ca s Display Properties ghi tr s cc linh kin.*Vi cc mch dao ng, t iu kin u (IC) d phn tch.Bc 2: Cho lin thng vi trnh PSpice phn tch hot ng ca mch.*Nhy chut trn thanh cng c lin thng vi trnh PSpice.*M ca s Simulation Setting xc lp cc iu kin phn tch.*Chn tiu hnh RUN cho chy trnh PSpice dng phn tch mch.*Sau cng xem cc kt qu trn trang th. Bn c kt qu nh hnh sau:

Mt th d: Dng PSpice tnh ton mt mch khuch i tn hiu nh vi s mch in v trong trang Capture CIS. Bi thc hnh s lm theo cc b?c sau:Bc 1: V s mch in trong Capture CIS v chy kiu phn tch Bias PointLy linh kin t ln bn v vi lnh Place Part.Cho ni mch qua cc chn ca linh kin vi lnh Place Wire.Bin son tr s ca cc linh kin (nhp chut 2 nhp nhanh trn cc tr s).*Hon chnh s mch in.Khi thit k mt tng khuch i, tr?c ht hy xc ?nh iu kin phn cc DC ca mch.Phn cc DCl s sp xp cc mc p DC v chn ?nh mc dng chy qua cc nhnh ca mch in. iu kin phn cc DC, cc t in cha c vai tr trong mch. Vy s mch in ch gm cc in tr, transistor v ?c v nh sau: (Bn xem hnh).

Sau khi v xong mch trn trang v Capture CIS, Bn cho chy trnh PSpice. Hy cho nhp chut vo tiu hnh New Simulation lin thng vi PSpice v t tn cho trang phn tch.Tiu hnh m trang New Simulation t tn cho trang phn tch.Sau khi t tn xong (tn t ty ), Bn s thy m ra mt ca s chn kiu dng phn tch (Bn xem hnh trang 12). Bn chn kiu phn tch lBias Point, xem kt qu phn cc tnh ca mch in. Chn xong nhn phm OK.

Tr li vng lm vic ca Capture CIS, Bn nhn tiu hnh

cho chy trnh PSpice. Sau mt lc, khi phn tch xong, trn vng lm vic ca Capture CIS, Bn c th xem kt qu bng cch nhn vo cc phm tiu hnh sau:Chn xem cc mc p phn cc DC trn cc ?ng ni ca mch in.

PSpice tnh ton xong v cho thy cc mc p DC trn cc ?ng ni ca mch in. xem dng in chy vo ra trn chn ca cc linh kin v dng in chy qua cc nhnh ca mch, Bn chn tiu hnh sau:Chn xem cc dng in phn cc DC chy qua cc nhnh ca mch in.PSpice tnh ton xong v cho thy cc dng in DC chy trn cc nhnh ca mch in.T cc kt qu trn Bn bit ?c iu kin phn cc tnh ca mch c ng yu cu khng. Nu mch phn cc ng. Nh vy c th chuyn qua b?c 2.Bc 2: Chy trnh PSpice phn tch mch in theo bin tn sChy lnh AC Sweep kho st c tnh bin tn v pha tn ca mch khuch i trn.Khi mch khuch i trn ly ?c phn cc tt. By gi hy cho tn hiu vo kch thch mch. Lc ny cc t in s c vai tr quan trng trong mch.Chng ta dng cc t ha lm t lin lc (bt cu cho tn hiu i qua) v dng lm t lc. S mch in v thm nh sau:

Ghi ch: v s ny. Bn dng lnh Place Part (g phm tt P) m kho ly ra cc t in cho ni vo mch.Khi ang sp xp cc linh kin trn mch. Bn c th dng cc phm tt sau xoay h?ng cc linh kin.G phm H (Horizontal) lt ngang k hiu linh kin ang chn.G phm V (Vertical) lt dc k hiu linh kin ang chn.G phm R (Rotation) quay k hiu linh kin ang chn.Nh vy, trn mch in chng ta cho mt ngun tn hiu dng Sin, c bin gi khng i l 1VAC (Tn s ca tn hiu thay i v s khai bo sau). Ngun tn hiu ny s kch thch mch, dng PSpice kho st cc mc p t?ng ng ng ra. kiu phn tch ny, bin ca trc ngang (trc honh, trc X) s l tn s.Bn hy a chut n nhp trn tiu hnh m trang chn kiu phn tch mch. Bn s thy hin ra ca s Simulation Settings nh hnh sau:Trong ca s Simulation Settings, Bn chn kiu phn tch AC Sweep/Noise.Lc ny hy xc ?nh di tn s m Bn mun cho phn tch mch.

Trong Start Frequency: Bn g vo con s cho bit mun bt u phn tch tn s no (g s 10, c ngha l tn s bt u l 10Hz).Trong End Frequency: Bn g vo con s cho bit s kt thc phn tch tn s no (g vo s 1Meg, c ngha l tn s kt thc l 1Mega-Hz ).Trong Points/Decade: Bn g vo con s xc ?nh s im phn tch trong mt b?c 10 (g vo s 100, c ngha l trong mt khong 100, hy tnh 100 im).Sau khi chn ?nh xong, nhn OK ng ca s v tr v vng lm vic ca Capture CIS. By gi hy ni vo mch mt ng d (in p) xem kt qu. Bn c th t ng d ng ra trn ?ng ni gia t C2 v in tr R6 (Bn xem hnh ).By gi, Bn hy nhp trn tiu hnh Run PSpice cho phn tch mch.Sau khi PSpice phn tch xong. Bn s c kt qu hin ra trn trang th (xem hnh).

?ng cong cho thy p ng bin tn ca mch khuch i (vi cc tn hiu c tn s trn 100KHz th bin bt u gim xung).v Bn cng c th xem ?ng cong pha tn. Hy m ca s Add Trace (Bn xem hnh).Trong ca s Function or Macro, Bn chn hm phase P(), tc xem pha ca tn hiu.Trong thanh Trace Expression, t bin V(6:2) vo hm Phase.Kt qu : ?ng cong pha tn nh hnh sau. ( tn s 100KHz, gc pha ca tn hiu tr gn 32).

Bc 3: Chy trnh PSpice phn tch mch in vi bin thi gianChy lnh Transient xem dng tn hiu trn cc im ni ca mch in.Khi mch khuch i c iu kin phn cc tt. By gi hy t mt tn hiu vo kch thch mch. Tn hiu c dng hnh Sin, tn s ly khng i (Th d: 1KHz), bin thay i theo dng sng Sin (Th d: 10mV). c ngun tn hiu ny kch thch mch, Bn khai bo thm trong ngun V2, dng khai bo nh sau:Sin 0 10mv 1KHz(Bn xem hnh).

Sau khi khai bo xong, hy m ca s Stimulation Settings v chn kiu phn tch l Transient.

Bn m ca s Analysis type v chn kiu phn tch l Time Domain (Transient).

Trong Run to time: Bn g vo khong thi gian phn tch. Vi tn hiu c tn s 1KHz th chu k s l 1ms, vy Bn phi chn khong thi gian phn tch di hn chu k c th xem ?c nhiu chu k tn hiu (Th d: g vo 3ms).Trong Start saving data after: Bn g vo con s xc ?nh thi im bt u cho hin tn hiu trn trang th (Th d: g vo s 0, tn hiu s hin ra t v tr 0s).Trong Maximum step size: Bn g vo con s ?nh b?c tnh (Th d: g vo s 0.01ms, c ngha l b?c ghi tn hiu l 0.01ms, ch : con s ny cng nh tn hiu s cng p, nhng tp tin d liu s ln).Sau khi chn xong, nhn nt OK ng ca s li v tr v vng lm vic ca Capture CIS. By gi hy chy Run c kt qu.

Tn hiu ng ra c dng hnh Sin, hy kho st mc mo ca tn hiu. Trong trang th, Bn nhp trn tiu hnh FFT (Phn tch chui Fourier, xem th dng ph tn):M xem th ph tn.Bn thy kt qu hin ra nh sau:

Ngoi vch tn hiu chnh cn xut hin nhiu vch tn hiu ph, iu ny cho thy tn hiu ng ra khng c dng thun Sin, ni cch khc tn hiu qua tng khuch i b lm mo (khng cn dng thun Sin nh tn hiu ng vo).Chng ta hy quan st tn hiu dng thun Sin ng vo. Hy t ng d ng vo. Bn s thy tn hiu hin ra trn trang th (Bn xem hnh).Tn hiu ng vo c dng thun Sin.Bin 10mv v tn s l 1KHz.

Kho st tn hiu thun Sin trn trang th ph tn. Bn thy:Mt tn hiu thun dng Sin s ch hin mt vch ?ng trn trang th ph tn.Bn hy xem tn hiu trn chn C ca Q1 bng cch t ng d trn chn ny. Bn s c kt qu nh hnh sau:Qua dng sng, Bn c th thy tn hiu ly ra trn chn C ca Q1 (hay trn chn B ca Q2), b mo phi tuyn trm trng.Tuy nhin khi tn hiu ny qua tng khuch i Q2, ng ra ca Q2 mc mo gim i, l u im ca mch khuch i 2 transistor ni tip, tng sau c th sa mo phi tuyn gy ra ca tng tr?c. Nh c c im ny m kiu mch khuch i ny hin rt thng dng (trong cc phn sau, chng ta cn phn tch chi