Kiu 1Kiu 1: Khuch i cng sut m thanh, tng tin khuch i lin lc qua
t (Mch lm vic vi bin tn hiu ln)Q1 l tng tin khuch i vi R1-R2 l cu
chia volt, ly p phn cc cho chn B ca Q1. R4 l in tr nh dng lm vic
cho Q1. R5 l in tr ly tn hiu hi tip nghch v R3 l in tr nh p cho chn
C. Tn hiu qua t lin lc ng vo C1 vo trn chn B v qua t lin lc ng ra
C3 ra trn chn C. C4 l t ha ln dng lc b tn hiu trn R4 lm mt tc dng
hi tip nghch gy ra do R4. Tng tin khuch i c cp ngun nui qua in tr
gim p R6 v t lc C2.Q2 l tng thc, n l tng khuch i cng sut nh hng A,
nn dng lm vic IC ly khong 10mA. R13 l in tr ly mc p trung im cp phn
cc cho chn B ca Q2. R14 l in tr lm tng n nh nhit cho Q2. R7 v R8
dng nh p chn C v cng dng nh dng cho Q2. Cc diode D1, D2, D3 dng ly
p phn cc DC cp cho cc transistor tng cng sut sa mo ti giao im ca tn
hiu. Tn hiu ly ra trn chn C cp cho tng ko y rp vi Q3, Q4. T C5 to
tc dng hi tip t c dng lm cn bng bin ca tn hiu ng ra (bin tn hiu phn
ln v phn xung bng nhau ).Q3, Q4 l 2 transistor h b (h tng b tc cho
nhau). Q3 l loi transistor npn v Q4 l loi transistor pnp. Nh vy khi
tn hiu ra trn chn C ca Q2 tng ln s lm Q3 dn in th Q4 ngng dn v ngc
li, khi tn hiu trn chn C ca Q2 gim xung, th Q4 dn in v Q3 ngng
dn.Q5 ghp phc hp vi Q3 v Q6 ghp phc hp vi Q4. Vi cc transistor ghp
phc hp thng c n nh nhit km, do ngi ta dng cc in tr R9 v R10 gia tng
h s n nh nhit cho Q5, Q6. R11 v R12 l cc in tr nh c cng dng cn bng
dng ko y qua loa. C7 l t ra loa, C7 phi ly tr ln v loa vn c tr khng
nh. Ngang loa mc mch lc zobel n nh tr khng ca loa trong dy tn tn
hiu m thanh.Cch ly phn cc DC: Vn cp cc mc volt phn cc.Ch : Vi mch
khuch i ko y ny, mc p ng ra trung im phi ly bng na mc p ngun. Chng
ta bit mc p trung im ph thuc vo mc p trn chn C ca Q2, vy khi iu
chnh tr ca in tr R13 cng s lm thay i mc p trung im. Trong mch vi
ngui nui l 30V, mc p trung im phi l 15V.* Dng lm vic ca Q1 ly khong
1mA.* Dng lm vic ca tng thc ly khong 10mA. trng thi tnh cc
transistor tng cng sut ko y c cho phn cc gn nh ngng dn, v tng cng
sut cho lm vic hng B mch cho hiu sut cao, khong 78%. Dng ton phn
khong 12mA l ttTn hiu ng vo v ng ra khng mo. Bin tn hiu ng ra khai
thc gn bng mc ngun nui (lc ln gn bng 15V v lc xung gn bng -15V).Ch
: li ca mch ph thuc vo t s ca 2 in tr mch hi tip nghch R16 v R5. Nu
gim R5, mc hi tip nghch s gim v mch s tng li v ngc li, nu tng tr ca
in tr R5, mc hi tip nghch ln s lm gim li.
Kiu 2Kiu 2: Khuch i cng sut m thanh, tng tin khuch i lin lc
thngT lc ngun C2Q2 l tng thc (tng thc cho lm vic theo kiu khuch i
cng sut nh hng A), chn B cho ni thng vo chn C ca Q1. Trn chn C c R6
R7 l in tr va nh p chn C v va nh dng IC. D1, D2, D3 dng ly p DC phn
cc cho cc transistor tng ko y nhm gim mo gy ra do ro p ( ng vo ca
cc transistor, trn chn BE u c ro p khong 0.5V). C4 l t c tr nh dng
to hi tip nghch vng tn s cao gi cho mch khng pht sinh dao ng t kch.
C3 l t hi tip t c dng lm cn bng bin tn hiu ng ra (gi cho bin tn hiu
ln bng vi bin ca tn hiu xung.Q3, Q5 v Q4, Q6 l cc transistor ghp
phc hp (cn gi l transistor darlington) dng lm tng khuch i cng sut
dng ko y. R8 v R9 dng lm tng h s n nh nhit cho cc transistor phc
hp. R10, R11 l cc in tr nh dng lm cn bng dng in qua cc transistor
cng sut. C5 l t ha c tr ln, dng cp dng in ko y cho loa. Ngang loa
dng mch lc zobel n nh tr khng ca loa trong dy tn tn hiu m thanh (
vng tn s cao, tr khng ca loa tng, lc mch lc zobel s lm gim tr khng
ca loa, vng tn s thp, tr khng ca loa nh, mch lc zobel s khng c tc
dng).Mch lm vic nh sau: Khi tn hiu dng sin qua t lin lc C1 vo chn B
ca Q1, tn hiu ny s c khuch i v cho ra trn chn C, n tc dng thng vo
chn B ca Q2, tn hiu ra trn chn C ca Q2 s vo thng tng cng sut ko y.
Khi bin tn hiu tng n s lm cho Q3, Q5 dn in v lc ny Q4, Q6 trng thi
ngng dn, v ngc li, khi bin tn hiu trn chn C ca Q2 gim xung, n s lm
cho Q4, Q6 dn in v lc ny th Q3, Q5 trng thi ngng dn. S ln xung ca
mc p trung im s qua t C5 to dng xoay chiu lm rung mn loa.Ch : li ca
mch ph thuc vo h s hi tip nghch to bi R5 v R13. Tng tr R13, mc hi
tip nghch s tng cao v li ca mch s gim v ngc li, nu cho gim tr ca
R13, mc hi tip nghch s gim v li ca mch s tng ln.
Kiu 3Khuch i cng sut vi ng vo dng vi sai, cc tng lin lc thng.mch
c p ng vng tn s thp tt, vng tn cao bin cn c nng ln.Q1,Q2 rp thnh
mch khuch i vi sai. R1, R5 l in tr cp dng phn cc cho chn B. Chn E
chung ca Q1, Q2 c cp dng hng (dng khng i). Tn hiu cho qua t lin lc
C1 vo chn B ca Q1 v ly ra trn chn C vo thng chn B ca tng Q4 (Q4 l
tng thc).Q3 rp thnh mch cp dng hng. Chn B cho ghim p vi diode zener
D1 v D1 c nh dng vi in tr R4. Cng dng in cp cho Q1, Q2 ly theo tr
ca in tr R3.Q4 l tng thc, n l tng khuch i cng sut nh hng A.
Transistor ny c cp dng lm vic bi Q5. Q5 l ngun bm dng hng, chn B
cho ghim p vi D1 v chn E nh dng vi R6. Cc diode D2, D3, D4 dng ly p
DC (mi diode ly 0.6V) cp cho cc transistor tng khuch i ko y sa mo
gy ra do ro p trn cc mi ni BE. T nh C3 dng to tc dng hi tip nghch
vng tn s cao gi cho mch khng pht sinh dao ng t kch.Q6, Q8 v Q7, Q9
l tng cng sut rp theo kiu ko y. Cc transistor ghp theo kiu phc hp
cn gi l cc transistor darlington. R7, R8 (phi ly tr bng nhau) l cc
in tr lm tng n nh nhit ca cc transistor darlington. D5 l diode lm
cn bng tr khng ng vo ca Q7 vi ng vo trn Q6, Q8. in tr R9, R10 dng
lm cn bng dng in qua transistor cng sut Q8, Q10. T C4 v R13 lm mch
lc zobel gi cho tr khng ca loa khng thay i trong dy tn ca tn hiu m
thanh.t im ca kiu mch tng m ny l ng vo dng khuch i vi sai nn c tnh
khng nhiu cng sai rt tt, ng ra khng dng t ra loa nn c p ng vng tn s
thp rt tt.Ch : li ca mch ty thuc vo t s hi tip nghch to bi R5 v
R11. Nu tng tr ca R11, tc dng hi tip nghch s ln, li ca mch s gim v
nu gim tr ca R11, tc dng hi tip nghch s nh v li ca mch khuch i s
tng.t im ca kiu mch tng m ny l ng vo dng khuch i vi sai nn c tnh
khng nhiu cng sai rt tt, ng ra khng dng t ra loa nn c p ng vng tn s
thp rt tt.Khi ly phn cc cho mch ny, iu cn thit nht l mc p ng ra phi
bng 0V hay gn bng 0V. Qua cc mc volt cp cho cc chn E, B, C chng ta
thy cc transistor tng cng sut c phn cc trng thi gn ngng dn, ngha l
tng ko y cho lm vic theo hng B, nh vy hiu sut ca mch mi c nng cao,
khong 78%Vi ngun cp dng hng rp vi Q1, do dng in tr nh dng R3 = 1K,
nn mc dng hng s l 1.5mA, dng ny cp cho Q1, Q2. Q4 lm vic vi mc dng
l 19.92mA, y l dng hng c cp bi Q5 vi in tr nh dng l R6 (120). Dng
ton phn ca mch l 30.79mA.
