Mt s mch khuch i tn hiu(1) Khuch i dng cho ng ni dng in dung.

ng ni dng chuyn i sng m thanh ra dng tn hiu in, ng ni dng in dung trong c mt transistor FET, trn chn cng (chn Gate), ngi ta t mn rung tnh in trng, quen gi l mn in chm, khi sng m thanh lm rung mn tnh in, n s lm thay i rng ca knh dn dng nm bn trong transistor FET v to ra tn hiu xut hin trn mt in tr t trn chn dn (chn Drain). Trong mch: X1 l microphone, l ng ni dng in dung, n c phn cc vi chn v cho ni masse v chn cn li qua in tr R5 ni ln ngun dng. Khi Bn ni vo micro, mn tnh in b lm rung, n s lm "co gin" knh dn in trong transistor FET, dng chy ra trn chn Drain qua in tr R5 v ngun, lc ny trn chn Drain s xut hin tn hiu m thanh.

Mch khuch i dng transistor Q1, vi R2 l in tr nh mc p cho chn C v in tr R1 dng cp phn cc cho chn B v in tr R3 dng ly tn hiu cho chn E to tc dng hi tip nghch. mch lm vic trong vng khuch i, mc p trn chn B phi cao hn chn E khong 0.6V (mi ni BE phi cho phn cc thun) v mc p chn C cao hn mc p chn B (mi ni CB phi cho phn cc nghch), thng mc p trn chn C ly khong 1/2 mc p ca ngun nui. Dng lm vic ca transistor ly khong 0.5mA l . Trong mch ny, tn hiu m thanh pht ra t ng ni in dung cho qua t lin lc 1uF a vo chn B v sau khi c khuch i tn hiu ly ra trn chn C v cho qua t lin lc 10uF cp cho ti R6. Trn ng ngun t thm mch lc ngun vi in tr R4 v t C1. (2) Khuch i dng cho ng ni dng in ng

Microphone in ng gm c mt cun dy rt nh gn trn mn run v t bn trong l mt nam chm vnh cu kh mnh. Khi Bn ni vo micro

in ng, mn rung s lm cho cun dy chuyn ng vo ra trn mt nam chm, v theo nh lut Faraday, trn hai u ca cun dy s xut hin in p tn hiu. Vy micro in ng to ra tn hiu m thanh bng s rung ca mt cun dy t gn mt nam chm vnh ca. Tn hiu ny cn rt nh (nh hn loi micro in dung), nn cn khuch i. Trong mch: Q1 l transistor khuch i cho lm vic theo kiu ly chn B lm chn chung, Bn thy chn B cho ni masse qua t C4. Kiu khuch ai ny c cc c im sau: * Tr khng ng vo trn chn E nh, nn rt ph hp vi loi micro in ng, d to c s phi hp ng tr khng, nh vy cng sut tn hiu ly vo s cc i. Tr khng ng ra ln, nn cho li in p cao. * Mch khuch i ly chn B lm chn chung cho li in p, khng cho li dng in. in p tn hiu ly ra trn chn C ln hn in p tn hiu a vo chn E, nhng dng ng vo l IE th gn bng dng ng ra IC nn khng c li v dng in. * Mch khuch i khng o pha. Khi tn hiu lm in p chn E tng thi in p tng ng trn chn C cng tng v ngc li, khi in p trn chn E gim th in p trn chn C cng gim theo. Trong mch: R2, R3 v t C4 cp mc volt phn cc cho chn B. in tr R1 dng nh mc dng lm vic IE cho transistor. in tr R4 dng nh mc p phn cc cho chn C. Tn hiu qua t lin lc C5 a vo chn E v tn hiu ly ra trn chn C qua t lin lc C6 a n chit p RV1. T y tn hiu s cho qua tng khuch i tng bin vi Q2, v tng khuch i m vi Q3. Ghi ch: Do tr khng ng vo trn chn E rt nh, nn tr ca t lin lc trn chn ny, t C5, Bn phi ly ln trnh lm mt cc tn hiu vng tn s thp. Transistor Q2 l tng khuch i ly chn E lm chn chung, nn tn hiu cho vo chn B v tn hiu ly ra trn chn C. Trong mch: R5 l in tr nh mc p trn chn C, R6 l in tr nh mc dng lm vic chy vo

trn chn E v R8 l in tr cp mc p phn cc cho chn B. Q3 l tng khuch i m vi tn hiu vo trn chn B v ly ra trn chn E. Kiu mch khuch i ny ly chn C lm chn chung, chn C cho ni vo ng ngun DC, mch khuch i C chung c cc c im sau: * Mch cho li dng in, dng tn hiu ng ra IE ln hn dng tn hiu ng vo IB, khng cho li in p, in p tn hiu ng ra VE gn bng in p tn hiu ng vo VB. * Tr khng ng vo rt ln, tr khng ng ra nh nn kh nng mang ti ca n tt hn. * Mch khuch i khng c tnh o pha. in p tn hiu vo trn chn B tng th in p tn hiu ra trn chn E cng tng theo, v ngc li tn hiu vo gim th tn hiu ng ra cng gim theo. Ngi ta ly tn hiu ra trn chn E ca Q3 trn in tr R7, cho qua t lin lc C9 tip tc i vo cc tng khuch i chn tn hay khuch i cng sut. Trn ng ngun cng t mch lc vi in tr R9 v t C8. (3) Tin khuch i, dng khuch i cc tn hiu nh.

Kiu mch khuch i ny hin rt thng dng, mch dng 2 transistor lin lc thng. Khi Bn phn tch mt mch khuch i, trc ht hy xt n iu kin phn cc tnh. cc transistor lm vic trong vng khuch i, mi ni BE phi cho phn cc thun v mi ni CB phi cho phn cc nghch, lc dng ht ti in phun ra t chn E s chy gn ht vo chn C v chy ra trn chn C, v lc ny, chng ta s dng mc volt bin i trn chn B lm tng gim dng in ny. Trong mch: R1 l in tr nh mc p trn chn C ca Q1, v R2 l in tr nh mc dng chy vo chn E ca Q1. R5 l in tr cp mc p phn cc cho chn B ca Q1. R3 l in tr nh mc p trn chn C ca Q2 v R4 l in tr nh mc dng chy vo chn E ca Q2. Khi kim tra mc p DC trn mch, chng ta thy Q1, Q2 c cho phn cc lm vic trong vng khuch i. Tn hiu cho qua t lin lc C1 vo chn B ca Q1, sau khi c khuch i, tn hiu ly ra trn chn C ca Q2 qua t lin lc C2 n ti.

Trong mch dng t C3 lm tng li ca Q2. trnh hin tng dao ng boating, chng ta t mch lc R6, C4 trn ng ngun. Do 2 tng khuch i rp theo kiu E chung, nn mch ny cho li rt ln, nh vy chng ta c th dng ng hi tip nghch ci thin cht lng ca mch khuch i. (4) Khuch i m sc, cn gi l khuch i chnh Bass - Treble. Tn hiu m thanh tai ngi nghe c nm trong dy tn s t 20Hz n 20000Hz. Ngi ta chia dy tn ny ra lm 3 on: * on t 20Hz n 400Hz gi l m trm, hay Bass * on t 400Hz n 3000Hz gi l m trung, hay Medium * on t 3000Hz n 20000Hz gi l m bng, hay Treble Khi nghe nhc hay khi nghe li thoi, c ngi thch nghe m trm, li c ngi thch nghe m bng, mi ngi mi , do vy ngi ta rp mch khuch i c chc nng iu chnh bin ca cc tn hiu m thanh theo tn s. Mch ph bin nht l dng mch lc Baxandal dng iu chnh bin tn hiu m thanh vng tn s thp, gi l nt chnh Bass v iu chnh tn hiu vng tn s cao, gi l nt chnh Treble. S mch in nh hnh sau:

Trong mch: Q1 l tng khuch i tng bin, rp theo kiu chn E chung, Q1 c phn cc vi in tr R2 dng nh mc p cho chn C, in tr R1 cp mc p phn cc cho chn B v in tr nh dnh R3, cn dng ly tn hiu trn chn E to tc dng hi tip nghch nhm n nh mch khuch i. Tn hiu a vo chn B qua t lin lc C1 v cho ly ra trn chn C qua t C2 vo mch lc, ti y ngi ta t mch lc tn Baxandal. Mch lc gm 2 nhnh: * Nhnh lc ly tn hiu c tn s cao, gm t C4, RV1 v t C5. Cc tn hiu c tn s cao d qua nhnh ny, cc tn hiu tn s thp b "chn li". Nh vy chng ta dng chit p RV1 ch chn bin cho cc tn hiu c tn s cao, RV1 thng gi l nt chnh ting bng. * Nhnh lc ly tn hiu tn s thp, gm R10, RV2, R11 v cc t C6, C7.

Mch cho thy ch c cc tn hiu tn s thp cho qua chit p RV2, cc tn hiu tn s cao u cho "i tt ngang qua" chit p ny. Trong nhnh ny, chng ta dng chit p RV2 ch chn bin cho cc tn hiu c tn s thp, RV2 thng gi l nt chnh ting trm. in tr R12 to phn cch gia cc nhnh lc tn. Sau khi ra khi 2 nhnh lc tn, mt cho tn s cao v mt cho tn s thp, thnh phn tn hiu m trm v m bng c cho "cng li" v cho qua t lin lc C8 a vo chn B ca tng khuch i vi Q2. Transistor Q2 c phn cc vi in tr R5 nh mc p trn chn C, in tr R4 cp p phn cc cho chn B, v in tr R6 to tc ng hi tip nghch trn chn E. Sau cng tn hiu ly ra trn chn C ca Q2 cho qua t lin lc C3 n ti, hay i tip vo cc tng khuch i khc. trnh "nh hng qua li gia cc tng do cng dng chung ng ngun", trn ng ngun DC chng ta t mch lc ngun vi in tr R7 v t C9. Mch lc ny s lc sch cc tn hiu ca cc tng nhim vo ng ngun, trnh c hin tng dao ng ngoi mun. (5) Khuch i cng sut m tn, cp tn hiu bin ln cho ti.

tn hiu c cng sut ln dng cp cho cc loi ti nh cc loa trong ng nghe hay loa in ng, ngi ta lp rp cc mch khuch i cng sut lm vic vi tn hiu bin ln. Sau y l vi mch thng dng, d rp, c hi rp thnh cng cao.(a) Khuch i ng ra dng cho ng nghe

c cng sut tn hiu ln cp cho cc loa nh t trong cc ng nghe, chng ta c th rp mch theo s trn. Trong mch: Q1 l transistor pnp rp theo kiu chn E chung, tn hiu m thanh t ngoi qua t lin lc C1 v in tr gim bin R9 a vo chn B ca Q1 v ly ra trn chn C a thng vo chn B ca Q3, y transistor Q2 dng nh mt ngun cp dng hng, n cp dng phn cc ln cho Q3 nhng li c tr khng AC rt ln, nn khng gy tn tht tn hiu trn chn C ca Q3. Sau cng tn hiu qua t lin lc C4 n cc loa nh t trong ng nghe. Mch c phn cc nh sau: Cc in tr R1, R2, R3 cp p phn cc cho chn B ca Q1. R6 l in tr nh mc dng lm vic cho Q1. T C3, v in tr R3 dng lm mch hi tip t c nhm tng tr khng ng vo

cho Q1. Cc diode D1, D2 v in tr nh dng R7 dng to ra mc in p c nh gi cho mc p trn chn B ca Q2 khng thay i v dng Q2 lm ngun cp dng hng vi R8 l in tr nh mc dng hng. Q3 l tng khuch i ng ra, ly thng tn hiu trn chn C ca Q1, y in tr R4 dng tng h s n nh nhit cho Q3. T C4 l t ng ra, vi R10 l in tr dng n nh hot ng ca t C4, trnh cho mt chn ca t C4 khng b trng khi mch khng cm ng nghe. trnh nh hng qua li gia cc tng khuch i do dng ng ngun chung, chng ta cng t mch lc nhiu R5, C2 trn ng ngun DC. (b) Khuch i ng ra dng cho Loa C rt nhiu kin mch khuch i cng sut m tn. Sau y chng ta th rp mt kiu mch Ampli rt ph dng.

Mch c rp vi 6 transistor, cng dng ca mi transistor nh sau: * Q1 l transistor pnp, dng lm tng khuch i ng vo. Ngi ta dng 2 in tr R1, R2 ly p cp cho chn B phn cc, chn E nh dng lm vic vi in tr R5, lc ngun dng in tr R4 v t C2. Tn hiu cho

qua t lin lc C1 vo chn B ca Q1, tn hiu ly ra trn chn C cho ghp thng vo tng khuch i thc Q2. Trn chn E t t C3 v in tr R11 dng ly tn hiu hi tip nghch nhm nh li ton phn ca mch tng m. * Q2 l transistor npn, dng lm tng thc, n c thit k cho lm vic theo dng cng sut nh hng A. Tn hiu cho vo chn B, chn E cho ni masse ly dng. Trn chn C t 2 diode 1N4148 ly ra mc p DC cp phn cc cho cc tng ko y, trnh tc dng ca ro p, nhm sa mo ti giao im tn hiu. R6, R7 l 2 in tr nh mc dng lm vic cho Q2, mc p phn cc trn chn C ca Q2 ly khong na mc p ngun nui. T C4 ly tn hiu ng ra hi tip t c v tng thc nhm lm cn bng bin tn hiu trn v di ng ra. Dng t nh C6 to hi tip nghch ch i vi cc tn hiu vng tn s cao nhm trnh cho mch khng pht sinh dao ng t kch. Khi mch dao ng t kch vng tn s cao, cc transistor cng sut s b rt nng v b h. * Q3, Q4 l 2 transistor h b npn v pnp dng lm tng khuch ai ko y. Cp transistor ny c mi tham s u ging nhau, n ch khc l mt npn v mt kia l pnp. Vi cp transistor h b ngi ta khng cn dng thm mch o pha. Khi tn hiu ra trn chn C ca Q2 tng ln, n s lm cho Q3 dn in v lc ny Q4 tt, v ngc li khi tn hiu ra trn chn C ca Q2 gim xung, n s lm cho Q4 dn in v lc ny Q3 tt. R8 v R9 l 2 in tr c tr s bng nhau v dng lm tng h s n nh nhit cho tng cng sut rp theo kiu phc hp. * Q5, Q6 l 2 transistor npn dng lm tng cng sut. c dng in tn hiu mnh ngi ta dng transistor cng sut Q5 cho ghp phc hp vi Q3 v dng transistor cng sut Q6 cho ghp phc hp vi Q4. Khi Q3 dn, Q5 s dn mnh hn v to iu kin cho t ra loa C5 np dng in ca ngun nui, dng ny c th dng ko mn loa vo. Khi n Q4 dn, Q6 s dn mnh hn v to iu kin cho t ra loa C5 x dng in qua loa, dng ny s y mn loa ra. T C5 l t cp dng ko y cho loa, t ny phi ly t ha c tr in dung ln. Ngang loa ngi ta t mch lc zobel n nh tr khng ca loa trong dy tn tn hiu m thanh nhm trnh dng mo cng sut.

Trong mch ny, c 2 h thc Bn cn nh: * H thc dng nh li ton mch:

Trong : KF l li ton phn. R5 l in tr nh dng trn chn E ca Q1, R11 l in tr ly tn hiu hi tip nghch * H thc dng tnh cng sut ly c trn loa:

Trong : Vcc l mc p ngun nui. RL l tr khng ca loa. (c) Khuch i cng sut m tn dng mch tch hp IC. Trn phng dn thc dng, khi cn c cc mch tng m cng sut ln, ngy nay ngi ta t dng transistor v cc linh kin phn lp rp mch. V sao? V trn th trng hin c v s cc IC cng sut m tn, dng cc IC ny cng vic lp rp mch tng m s rt nhanh, gn nh. Di y ti gii thiu vi mch in Bn tham kho v lm thc hnh cho quen tay.

Mch rp vi mt ic tng m nh, c kch c nh ic 555, nhng trong ic c 2 mch tng m c lp c th rp dng mch tng m stereo hay rp theo kiu mch mono BTL. Khi rp mt ic tng m, Bn c th lm theo 3 bc: Bc 1: Tm chn cp ngun. Thng c mt chn ni masse, mt chn ni vi ngun dng v thng khi cn c mt chn dng mc t lc cho tng ngun tin khuch ai. Bc 2: Tm chn ng vo v ng ra. Trn chn ng vo Bn dng chit p iu chnh mc tn hiu. C nhiu IC ng vo phi dng t lin lc bo ton mc volt phn cc DC, c IC cho ni thng, v mc p phn cc ng cho mc 0V. Tm chn ng ra, ng ra thng c mc p phn cc

cho bng na mc p ngun nui. Tn hiu cp cho Loa thng qua mt t in ha hc ln. Bc 3: Ch n cc mch hi tip, cc mch in ph khc, thng c cc mch sau: * Mch hi tip nghch, tn hiu ng ra tr tr li ng vo o. Tr in tr ly tn hiu hi tip nghch cng dng nh li cho ton mch.size=3]* Mch hi tip t c. Dng t hi tip t c ly tn hiu ng ra tr v tng thc c th lm cn bng bin tn hiu ln xung ng ra.

* Dng t tr nh hi tip b pha hay hi tip nghch gi cho mch khng t pht sinh dao ng t kch. * Dng mch lc zobel n nh tr khng ca loa trnh hin tng mo cng sut do tr khng ca loa thay i theo tn s. Trong mch: * C1 l t lin lc ng vo, RV1 l chit p dng lm nt chnh mc m lng, tn hiu a vo chn 4 cho knh 1 v chn 6 cho knh 2. * Tn hiu ra trn chn 1 cho knh 1 v chn 3 cho knh 2, ti y tn hiu cho qua t ra loa C4 cp dng in ko y lm rung mn loa. T C5 v in tr R3 dng lm mch lc zobel n nh tr khng ca loa nhm trnh hin tng sai cng sut. Mc p phn cc trn cc chn ng ra phi bng 1/2 mc p ngun nui Vcc. * Ngi ta dng cu chia volt vi in tr R2 v R3 ly mt phn tn hiu ng ra qua t lin lc C2 cho hi tip nghch v chn s 8 cho knh 1 v chn s 5 cho knh 2. ng hi tip nghch c tc dng ci thin cht lng ca tn hiu m thanh. * IC lm vic vi chn s 4 ni masse v chn s 8 noi vo ngun nui Vcc. IC c th lm vic vi mc ngun nui t 3V n 12V.

Trong mch: Chit p R1 dng lm nt chnh Volume, C1 l t lin lc ng vo, tn hiu a vo IC qua chn s 1. Tn hiu cho ra trn chn s 4 qua t ha ln C3 cp dng in ko y lm rung mn loa. Ngang loa dng mch lc zobel trnh hin tng mo cng sut do tr khng ca loa thay i theo tn s. Dng cu chia volt R2, R3 ly mt phn tn hiu ng ra qua t lin lc C2 cho hi tip nghch v chn s 2 ci thin cht lng ca m thanh. IC lm vic vi chn s 3 cho ni masse v chn s 5 ni vo ng ngun Vcc. IC c th lm vic vi mc ngun thay i t 6V n 18V, chng ta bit cp mc ngun nui cng cao cng sut ly ra cng ln. Ch : Khi kim tra mch, o mc p phn cc trn chn s 4 ca IC phi c mc p trung im, ngha l bng na mc p ca ngun nui. Tr ca in tr R3 dng nh mc hi tip nghch, ly tr R3 cng nh, mc hi tip nghch cng t, li s ln, cng sut ra ln nhng cht lng m

thanh km hn, khi ly tr R3 ln, ngc li cng sut ra yu hn nhng cht lng m thanh s nghe hay hn.

Trn xe hi Bn c th dng ic HA13118 rp mch tng m 2 knh ra 2 loa hay kiu mch mono BTL ra 1 loa ly cng sut ra ln khi IC lm vic vi mc ngun nui thp. Trong mch: Tn hiu m thanh c ly ra trn nt chnh mc m lng cho qua t lin lc C10 a vo chn s 3, y gn t nh C11 lc b nhiu tn s cao. Trn ng vo o cho gn t lc C1 ly li ln. Tn hiu knh 1 cho ra trn chn s 15, trong IC c ng cp tn hiu cho knh 2 v tn hiu cho ra ca knh 2 trn chn s 8. Chng ta gn loa ly tn hiu ra dng BTL trn chn s 15 v chn 8. T C5 v C6 l cc t hi tip t c dng cn bng bin ko y ng ra, n ly tn hiu ng ra cho hi tip v chn 14 v chn 10. ng ra cng t cc mch lc zobel vi t C7, R1 v t C8, R2, cng dng ca mch lc zobel l n nh tr

khng ca loa, trnh hin tng mo cng sut do tr khng ca loa thay i theo tn s. IC lm vic vi chn 12 cho ni masse, chn 13 ni vo ng ngun Vcc, t 8V n 18V. Trn cc chn 2, chn 5 gn t lc C4 v C3. Trn chn s 4 ca ng vo knh 2 cho ni masse v chn 6 gn t ni masse C2. Trong mch IC phi cho gn trn ming nhm lm ngui gi cho IC khng qu nng.

S trn cho thy cc dng IC TDA7209 rp mch tng m c cng sut ra 50W. IC ny lm vic vi dng ng ngun i xng. c ngun nui dng i xng, Bn dng bin p ngun trn cun th cp phi c ra dy gia dng lm dy masse, k dng cu nn dng vi 4 diode c ng ngun V+ v ng ngun V-. n nh cc mc volt ngun ra, chng ta gn cc t ha ln dng lm kho cha in v n p. IC TDA7209 lm vic vi cc chn 7, 13 ni vo ng ngun dng, cc chn 1, 8, 15 cho ni vo ng ngun m v chn s 4 cho ni vo ng masse. Tn hiu qua chit p chnh bin cho qua t lin lc C1 v in tr gim bin R1 sa mo ting a vo chn s 3. in tr R2 dng n nh tr khng ng vo v t nh C2 dng lc b tn hiu nhiu tn s cao. Tn hiu ly ra trn chn s 14 cho cp thng vo loa, chng ta bit khi dng kiu mch tng m chy ngun nui i xng th trn ng ra khng cn dng t ha lm t xut m. y t C6 dng ly tn hiu hi tip t c lm cn bng bin tn hiu ko y ng ra. in tr R3, R4 v t C3 dng ly mt phn tn hiu ng ra cho ng hi tip nghch sa mo ting v ci thin cht lng m thanh. IC ny c chn s 10 dng tm lm cm loa v chn s 9 cho IC vo trng thi tt ch.Theo phuclanshop