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1 Mch khuch i 1.1 Khi nim v mch khuyh i . Mch khuych i c s dng trong hu ht cc thit b in t, nh mch khuych i m tn trong Cassete, mply, Khuych i tn hiu video trong Ti vi mu v.v C ba loi mch khuych i chnh l : * Khuych i v in p : L mch khi ta a mt tn hiu c bin nh vo, u ra ta s thu c mt tn hiu c bin ln hn nhiu ln. * Mch khuych i v dng in : L mch khi ta a mt tn hiu c cng yu vo, u ra ta s thu c mt tn hiu cho cng dng in mnh hn nhiu ln. * Mch khuych i cng xut : L mch khi ta a mt tn hiu c cng xut yu vo , u ra ta thu c tn hiu c cng xut mnh hn nhiu ln, thc ra mch khuych i cng xut l kt hp c hai mch khuych i in p v khuych i dng in lm mt. 1.2 Cc ch hot ng ca mch khuych i. Cc ch hot ng ca mch khuych i l ph thuc vo ch phn cc cho Transistor, tu theo mc ch s dng m mch khuych i c phn cc K ch A, ch B , ch AB hoc ch C a) Mch khuych i ch A. L cc mch khuych i cn ly ra tn hiu hon ton gin vi tn hiu ng vo.

Mch khuych i ch A khuych i c hai bn chu k tn hiu ng vo * Transistor hot ng ch A, ta phi nh thin sao cho in p UCE ~ 60% 70% Vcc. * Mch khuych i ch A c s dng trong cc mch trung gian nh khuych i cao tn, khuych i trung tn, tin khuych i vv.. b) Mach khuych i ch B. Mch khuych i ch B l mch ch khuych i mt na chu k ca tn hiu, nu khuych i bn k dng ta dng transistor NPN, nu khuych i bn k m ta dng transistor PNP, mch khuych i ch B khng c nh thin.

Mch khuych i ch B ch khuych i mt bn chu k ca tn hiu ng vo.

* Mch khuych i ch B thng c s dng trong cc mch khuch i cng xut y ko nh cng xut m tn, cng xut mnh ca Ti vi, trong cc mch cng xut y ko , ngi ta dng hai n NPN v PNP mc ni tip , mi n s khuych i mt bn chu k ca tn hiu, hai n trong mch khuych i y ko phi c cc thng s k thut nh nhau: * Mch khuych i cng xut kt hp c hai ch A v B .

Mch khuych i cng xut mply c : Q1 khuych i ch A, Q2 v Q3 khuych i ch B, Q2 khuych i cho bn chu k dng, Q3 khuych i cho bn chu k m. c) Mch khuych i ch AB. Mch khuych i ch AB l mch tng t khuych i ch B , nhng c nh thin sao cho in p UBE sp s 0,6 V, mch cng ch khuych i mt na chu k tn hiu v khc phc hin tng mo giao im ca mch khuych i ch B, mch ny cng c s dng trong cc mch cng xut y ko . d) Mch khuych i ch C L mch khuych i c in p UBE c phn c ngc vi mc ch ch ly tn hiu u ra l mt phn nh ca tn hiu u vo, mch ny thng s dng trong cc mch tch tn hiu : Th d mch tch xung ng b trong ti vi mu.

ng dng mch khuych i ch C trong mch tch xung ng b Ti vi mu. 2 Cc kiu mc ca Transistor 2.1 Transistor mc theo kiu E chung. Mch mc theo kiu E chung c cc E u trc tip xung mass hoc u qua t xung mass thot thnh phn xoay chiu, tn hiu a vo cc B v ly ra trn cc C, mch c s nh sau :

Mch khuych i in p mc kiu E chung , Tn hiu a vo cc B v ly ra trn cc C Rg : l in tr ghnh , Rt : L in tr nh thin, Rpa : L in tr phn p . c im ca mch khuych i E chung. Mch khuych i E chung thng c nh thin sao cho in p UCE khong 60% 70 % Vcc.

Bin tn hiu ra thu c ln hn bin tn hiu vo nhiu ln, nh vy mch khuych i v in p. Dng in tn hiu ra ln hn dng tn hiu vo nhng khng ng k. Tn hiu u ra ngc pha vi tn hiu u vo : v khi in p tn hiu vo tng => dng IBE tng => dng ICE tng => st p trn Rg tng => kt qu l in p chn C gim, v ngc li khi in p u vo gim th in p chn C li tng => v vy in p u ra ngc pha vi tn hiu u vo. Mch mc theo kiu E chung nh trn c ng dng nhiu nht trong thit b in t. 2.2 Transistor mc theo kiu C chung. Mch mc theo kiu C chung c chn C u vo mass hoc dng ngun (Lu : v phng din xoay chiu th dng ngun tng ng vi mass), Tn hiu c a vo cc B v ly ra trn cc E, mch c s nh sau :

Mch mc kiu C chung , tn hiu a vo cc B v ly ra trn cc E c im ca mch khuych i C chung . Tn hiu a vo cc B v ly ra trn cc E Bin tn hiu ra bng bin tn hiu vo : V mi BE lun lun c gi tr khong 0,6V do khi in p chn B tng bao nhiu th p chn C cng tng by nhiu => v vy bin tn hiu ra bng bin tn hiu vo . Tn hiu ra cng pha vi tn hiu vo : V khi in p vo tng => th in p ra cng tng, in p vo gim th in p ra cng gim.

Cng ca tn hiu ra mnh hn cng ca tn hiu vo nhiu ln : V khi tn hiu vo c bin tng => dng IBE s tng => dng ICE cng tng gp ln dng IBE v ICE = .IBE gi s Transistor c h s khuych i = 50 ln th khi dng IBE tng 1mA => dng ICE s tng 50mA, dng ICE chnh l dng ca tn hiu u ra, nh vy tn hiu u ra c cng dng in mnh hn nhiu ln so vi tn hiu vo. Mch trn c ng dng nhiu trong cc mch khuych i m (Damper), trc khi chia tn hiu lm nhiu nhnh, ngi ta thng dng mch Damper khuych i cho tn hiu kho hn. Ngoi ra mch cn c ng dng rt nhiu trong cc mch n p ngun (ta s tm hiu trong phn sau) 2.3 Transistor mc theo kiu B chung. Mch mc theo kiu B chung c tn hiu a vo chn E v ly ra trn chn C , chn B c thot mass thng qua t. Mach mc kiu B chung rt t khi c s dng trong thc t.

Mch khuych i kiu B chung, khuych i v in p v khng khuych i v dng in. 3 Cc kiu ghp tng 3.1 Ghp tng qua t in. * S mch ghp tng qua t in

Mch khuych i u t c hai tng khuych i c ghp vi nhau qua t in. trn l s mch khuych i u t trong i Cassette, mch gm hai tng khuych i mc theo kiu E chung, cc tng c ghp tn hiu thng qua t in, ngi ta s dng cc t C1 , C3 , C5 lm t ni tng cho tn hiu xoay chiu i qua v ngn p mt chiu li, cc t C2 v C4 c tc dng thot thnh phn xoay chiu t chn E xung mass, C6 l t lc ngun. u im ca mch l n gin, d lp do mch c s dng rt nhiu trong thit b in t, nhc im l khng khai thc c ht kh nng khuych i ca Transistor do h s khuych i khng ln. trn l mch khuych i m tn, do cc t ni tng thng dng t ho c tr s t 1F 10F. Trong cc mch khuych i cao tn th t ni tng c tr s nh khong vi nan Fara. 3.2 Ghp tng qua bin p . * S mch trung tn ting trong Radio s dng bin p ghp tng

Tng Trung tn ting ca Radio s dng bin p ghp tng. trn l s mch trung tn Radio s dng cc bin p ghp tng, tn hiu u ra ca tng ny c ghp qua bin p i vo tng pha sau. u im ca mch l phi hp c tr khng gia cc tng do khai thc c ti u h s khuych i , hn na cun s cp bin p c th u song song vi t cng hng khi mch khuych i mt tn s c nh. Nhc im : nu mch hot ng di tn s rng th gy mo tn s, mch ch to phc tp v chim nhiu din tch. 3.3 Ghp tng trc tip . * Kiu ghp tng trc tip thng c dng trong cc mch khuych i cng xut m tn.

Mch khuych i cng xut m tn c n o pha Q1 c ghp trc tip vi hai n cng xut Q2 v Q3. 4 Phng php kim tra mt tng khuch i 4.1 Trong cc mch khuych i ( ch A ) th phn cc nh th no l ng.

Mch khuych i c phn cc ng. Mch khuych i ( ch A) c phn cc ng l mch c UBE ~ 0,6V ; UCE ~ 60% 70% Vcc

Khi mch c phn cc ng ta thy , tn hiu ra c bin ln nht v khng b mo tn hiu . 4.2 Mch khuych i ( ch A ) b phn cc sai.

Mch khuych i b phn cc sai, in p UCE qu thp .

Mch khuych i b phn cc sai, in p UCE qu cao Khi mch b phn cc sai ( tc l UCE qu thp hoc qu cao ) ta thy rng tn hiu ra b mo dng, h s khuych i ca mch b gim mnh.

Hin tng mo dng trn s gy hin tng m thanh b r hay b nght cc mch khuych i m tn. Phng php kim tra mt tng khuych i. Mt tng khuych i nu ta kim tra thy UCE qu thp so vi ngun hoc qu cao sp s bng ngun => th tng khuych i c vn . Nu UCE qu thp th c th do chp CE( hng Transistor) , hoc t Rg. Nu UCE qu cao ~ Vcc th c th t Rt hoc hng Transistor. Mt tng khuych i cn tt thng thng c : UBE ~ 0,6V ; UCE ~ 60% 70% Vcc Ngun: hocnghe.com.vn

Cu phn p dng in tr R

in T ng Dng - in T ng Dng Trong mch in, gi s ta cn in p 6V t ngun cung cp 9v, ta phi s dng n cu chia p.

Gi s gi tr in tr l 1K v 1K, in p im gia 2 in tr s l 4,5v, c xc nh bng cng thc sau: U=UVxR2:(R1+R2) =>U=9x1:(1+1)=4,5V Cch tnh khc:

Cch tnh khc 1. Cng tng tr 1K + 2K = 3K 2. Chia in p cho tng tr 9v/3k = 3 3. Ly tr in tr ln hn nhn vi tr thu c bc 2: 2k x 3 = 6v Vy ch cn 2 con in tr ta c th c c nhng in p khc nhau.

Linh kin bn dn

Mch a Hi dng Transistor BJT thy mi ngi tranh lun v mch ny ri, nhng cha thy c bi vit no ni c th v mch Dao ng a hi ny. Nn e xin mn php post ln. Hi vng s gip dc my em mi hc v xin dc ch gio thm t cc anh tin bi Ch : Bn nn xem li qu trnh np x t in v bit s qua v BJT Gii thiu: B a hi (multivibrator) l mt mch dng thay i 2 trng thi n gin, VD nh: mch to dao ng, timer, Flip-flop N bao gm 2 linh kin khuch i (Transistor, bng n in t ) ni cho nhau qua cc t v tr. Dng thng gp nht l mch a hi (tp trung ni trong bi ny) v mch to dao ng c th to ra cc sng vung. Mch a hi: Mch a hi l loi n gin nht ca 1 b multivibrator, bao gm 2 con BJT mch cho, thm vo cc tr phn cc v 2 t ha thc hin qu trnh np x. Chng ta s tnh c chu k ca n qua R,C (ci ny dc hc cp 3 nhng b mt gc n tn H lun ) Mch bn di l mt mch VD n gin v thng dng gii thch mch a hi. Vi u ra l cc chn C ca BJT.

Gii thch hot ng ca mch: Tng tng BJT nh l 1 cng tc, trong 1 thi im (ngha l 1 trng thi ch c 1 BJT m) (c ht bi th bn hy suy ngh ti sao, by h c mch nh l nh vy ) V vy chng ta gi s ban u Q1 m, v Q2 ng. Trng thi 1: - in p ti Out1 ~ GND, bi v Q1 m m. - Side bn phi ca C1 (v Cc B ca Q2) bt u c np in t 0 cho n 0.6V. - R3 ko dng ti cc B ca Q1 ln. Nhng mi ni PN ti 2 cc B-E ngn cn in p ti ko qu 0.6V. - Dng in qua R4 np vo side phi ca C2 cho n khi bng V ngun. V R4 < R2 nn C2 np in nhanh hn C1. Khi cc B ca Q2 t ti 0.6V th Q2 bt u m, v xy ra dng hi tip dng: - Q2 lp tc a th ti side phi ca C2 v 0 (v Q2 m m) - V in p trong t in khng thay i nhanh c, cho nn p ti side tri ca C2 s thnh gn V ngun rt nhanh (v trc C2 np y l +V m), chnh xc l ch di 0V. - Q1 s tt v in p ti B ca Q1 bin mt (v C2). - R1 v R2 bt u lm cho dng np qua C1 thnh +V ngun Ri sau qua trng thi 2, ngc li vi lc u, y Q1 tt v Q2 m, nguyn l hot ng ging nh trng thi 1. Dng qua R1 np nhanh vo side tri C1 +V, cn dng qua R3 t t np side tri C2 ln 0.6V Q1 m Tnh ton tn s hot ng ca mch: T = t1 + t2 = ln(2)R2 C1 + ln(2)R3 C2 Chng ta thng quy nh khi lm mch nh sau: - t1 = t2 (50% duty cycle) - R2 = R3 - C1 = C2

V y l mch khi m phng:

Cp ngun v nh thin cho TransistorNi dung : ng dng ca Transistor, Cp ngun cho Transistor, nh thin ( phn cc ) cho Transistor hot ng, Mch phn cc c hi tip. 1. ng dng ca Transistor. Thc ra mt thit b khng c Transistor th cha phi l thit b in t, v vy Transistor c th xem l mt linh kin quan trng nht trong cc thit b in t, cc loi IC thc cht l cc mch tch hp nhiu Transistor trong mt linh kin duy nht, trong mch in , Transistor c dng khuych i tn hiu Analog, chuyn trng thi ca mch Digital, s dng lm cc cng tc in t, lm cc b to dao ng v v... 2. Cp in cho Transistor ( Vcc - in p cung cp ) s dng Transistor trong mch ta cn phi cp cho n mt ngun in, tu theo mc ch s dng m ngun in c cp trc tip vo Transistor hay i qua in tr, cun dy v v... ngun in Vcc cho Transistor c quy c l ngun cp cho cc CE. Cp ngun Vcc cho Transistor ngc v thun Ta thy rng : Nu Transistor l ngc NPN th Vcc phi l ngun dng (+), nu Transistor l thun PNP th Vcc l ngun m (-)

3. nh thin ( phn cc ) cho Transistor . * nh thin : l cp mt ngun in vo chn B ( qua tr nh thin) t Transistor vo trng thi sn sng hot ng, sn sng khuych i cc tn hiu cho d rt nh. * Ti sao phi nh thin cho Transistor n mi sn sng hot ng ? : hiu c iu ny ta hy xt hai s trn : trn l hai mch s dng transistor khuych i tn hiu, mt mch chn B khng c nh thin v mt mch chn B c nh thin thng qua Rt. Cc ngun tn hiu a vo khuych i thng c bin rt nh ( t 0,05V n 0,5V ) khi a vo chn B ( n cha c nh thin) cc tn hiu ny khng to ra dng IBE ( c im mi P-N phi c 0,6V mi c dng chy qua ) => v vy cng khng c dng ICE => st p trn Rg = 0V v in p ra chn C = Vcc s th 2 , Transistor c Rt nh thin => c dng IBE, khi a tn hiu nh vo chn B => lm cho dng IBE tng hoc gim => dng ICE cng tng hoc gim , st p trn Rg cng thay i => v kt qu u ra ta thu c mt tn hiu tng t u vo nhng c bin ln hn. => Kt lun : nh thin ( hay phn cc) ngha l to mt dng in IBE ban u, mt st p trn Rg ban u khi c mt ngun tn hiu yu i vo cc B , dng IBE s tng hoc gim => dng ICE cng tng hoc gim => dn n st p trn Rg cng tng hoc gim => v st p ny chnh l tn hiu ta cn ly ra . 3. Mt s mch nh thin khc . * Mch nh thin dng hai ngun in khc nhau . Mch nh thin dng hai ngun in khc nhau * Mach nh thin c in tr phn p c th khuch i c nhiu ngun tn hiu mnh yu khc nhau, th mch nh thin thng s dng thm in tr phn p Rpa u t B xung Mass. Mch nh thin c in tr phn p Rpa * Mch nh thin c hi tip . L mch c in tr nh thin u t u ra (cc C ) n u vo ( cc B) mch ny c tc dng tng n nh cho mch khuych i khi hot ng. Su tm

Hng dn cu hnh tn min

Bn ng k tn min ti mt cng ty khc. Bn thit k website hoc s dng dch v lu tr web (hosting) ti BLUESKY. website ca bn c th hot ng trn Internet. 1. Bn lin lc vi chng ti c h tr (support) ti thng tin trn a ch website : www.bluesky.vn 2. Bn truy cp lin kt ti qun tr tn min m bn c cung cp ti cng ty bn ng k tn min. VD : http://access.enom.com, http://dotvn.dotvndns.vn/login.php, http://domain.vinadots.net/ + Cu hnh DNS : DNS domain (Name Server) ca bn cn c tr n ns1.hostbs.com v ns2.hostbs.com + Cch 2 cu hnh IP : Tr cc record ca domain (www, @, mail, ftp, mx) n web server IP: 210.211.110.132 Sau khi cu hnh, nu bn tr IP th sau 10-30 pht s c hiu lc v website ca bn s bt u hot ng trn mng. Nu tr DNS bn s cn ch khong 12 ting hoc lu hn 48 ting c hiu lc. Mt s thng tin cn bit khi qun l tn min : Cc cch lin kt 1 tn min vi dch v lu tr web (hosting): + Tr DNS (Tn min c th tr trc tip ti Name server ni my ch chia s gi dch v lu tr web. V d : ns1.hostbs.com, ns2.hostbs.com) + Tr IP (Mi nh cung cp tn min u c my ch v Name server ring, h s cung cp Tool qun tr tn min cho khch hng cu hnh tn min tr v my ch m khch hng thu ca mt cng ty khc) + URL Frame (Trong trng hp khch hng c website hot ng trn mt tn min c lp, tn min mi ng k c th s dng vic tr URL Frame nhn ti tn min hot ng. Dch v URL Frame s to ra 1 Frame lin kt vi hosting. Khi ngi s dng duyt qua cc trang Web, a ch URL ca trnh duyt Web s vn gi nguyn l tn tn min ca bn, m bo tnh chuyn nghip cho Website) + URL Forwarding (Dch v URL Forwarding s t ng chuyn trnh duyt Web ca bn ti 1 Website no c sn khi ngi s dng truy cp ti tn min ca bn.) Hng dn nhanh A (Address) - Host + Record Name: mail, @, (@ thay cho gi tr rng) + Gi tr: [Nhp IP] (V d: 203.162.163.44) CNAME (Alias) + Record Name: www, ftp, @ (@ thay cho gi tr rng) + Gi tr: [Nhp tn host] (V d: tenmien.vn, mail.tenmien.vn, )

MX Mail Exchange + Record Name: @ (@ thay cho gi tr rng) + Gi tr: [Nhp tn host] (V d: tenmien.vn, mail.tenmien.vn, ) Email Forwarding + Record Name: admin, webmaster, (chnh l tn hp mail) + Gi tr: [Nhp a ch mail c tht] (V d: v d: mylove@yahoo.com) URL Frame + Record Name: @, www, www2 (@ thay cho gi tr rng) + Gi tr: [Nhp a ch trang web] (v d: http://www.tenmien.com) URL Redirect + Record Name: @, www, www2 (@ thay cho gi tr rng) + Gi tr: [Nhp a ch trang web] (v d: http://www.tenmien.com) SPF Sender Policy Framework + Loi: TXT + Record Name: @, smtp, (@ thay cho gi tr rng) + Gi tr: v=spf1 -all v=spf1 mx -all v=spf1 mx ptr -all v=spf1 a:[tenmien cua ban] mx ptr -all (v d: v=spf1 a:tenmien.vn mx ptr -all) v=spf1 a mx ptr -all