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GVHD: Nguyn Hng Minh
Thc tp Mch Tng T
Bi m u : Gii Thiu Mt S Linh Kin V Cch oI.Mc ch :
- Sinh vin lm vic trong phng my, s dng thnh tho phn mm v bit c tnh cht ca cc linh kin khi ghp vo mch, kho st kim nghim cc mch in t c hc trong phn mch tng t nh: kho st BJT, FET, ng dng Op-Amp, dao ng sin tn s thp v dao ng khng sin.Qua cho ta thy c s khc bit gia thc hnh v l thuyt, kh nng t nhn xt da trn cc hin tng v quan st gin xung.
- Gip ta xc nh chn ca cc loi: bin tr,diode,transistor.
- o th cc loi linh kin trn bit linh kin cn tt hay hng.
- Sau y l mt s linh kin thng s dung trong mch v cch o n:
1. Khi ta o th vi diode , th c diot vn hot ng tt , mt s hot ng khng ng v qu thi gian s dng nhiu ln nn linh b hng.
+ Hnh v :
+ Chn k ang s dng c dng in i t que ( que en: Khi o th ta xc nh c chn di l cc dng(+) ng vi chn 1, v ngc li chn ngn l cc m(-).
+ Cch xc nh trn l cch xc nh chung cho mi loi diode nhng trn thi trng c rt nhiu loi diode mi loi diode c mt hnh dang khc nhau .V sau y l mt s hinh nh v diode:
Diode pht quang (led ) diode zener
2. o transistor:(dy l cc m cn dy en l cc dng)
-u tin gi s que chn 1, t que en ra 2 chn cn li, ta thy c 1 chn que en khng ln.
Tng t ta que chn 2, tque en 2 chn cn li v ta thy mt chn que en khng ln.
Tip tc que chn 3 , th que en 2 chn cn li khng ln.
y khng phi l trnistor loi PNP
Ta que en chn 1 , th que chn 2,3 khng ln.
Tng t chn 2 cng vy.
que en chn 3 , que chn 2,3 u ln, t ta c th xc nh chn 3 l cc B => y l transistor loi NPN.
Hnh v :
S dng tr 100K , 1 u cm B(chn 3) gi s chn 1 l chn C, dy en vo cc C cho dy vo 2 chn th in tr rt ln (kim ng h ch gi tr ln), gi s chn 2 l cc C , cho dy en vo C , dy vo chn 1 ( ng h ch gi tr nh m khi ng h ch gi tr cng nh th phn cc thun ( iu chng t chn 2 l cc C , chn cn li l cc E.
Php o th th 2 : PNP: ngc li vi transitor NPN (s dng dy th cho dy en) th cc cc ( t c th suy ra cc cc.
-Hnh v:
Transistor PN
i vi transitor PNP th cc B l cc m, cc C,E l cc dng.
3. o linh kin bin tr :
M hnh : bin tr l linh kin th ng
C 3 chn , trong c 1 chn di ng v 2 chn c nh gi l chn 1 v chn 2. Dng Ohm k o in tr t chn di ng ti 2 chn c nh ta c :
S ln oChn 1Chn 2
Ln 110k5k
Ln 2 2k5k
Ln 31k250k
-Hnh v:
Bin tr
4. o linh kin SCR :
- Hnh v:
Linh kin SCR
- Cch o: SCR l linh kin c 3 chn G , A , K dng kch IG, i vo chn G, ra chn K. Chn G l que en, K l que th kim Ohm k ln. o G-K dng gii X10. o chn G-A, A-K c 2 u khng ln(2 chiu l o 2 que o) nu o khng ln th SCR b hng.
5. Gii thiu v Oscilloscope
- Hnh v:
Oscilloscope
- Cc nt iu khin ca Oscilloscope:
+ Nt iu khin Volt/DIV (s volt trn mt )
+ Time/DIV (thi lng trn 1 )
+ Position ln, xung
+ Position qua, li ( chnh dng sng hin th v tr nhn nht)
+ Thanh iu khin Vert mode (chn hiu th knh 1, knh 2, hay c 2)
+ Nt Triglevel (i khi dng sng b tri, ta chnh nt ny dng sng ng li)
+ Thanh iu khin AC-GND-DC
II.Ni Dung: Mn hc ny nhm trang b cho sinh vin
- Kin thc: + Nhn bit cc linh kin v cc mch khi thc hnh trn my.
+ Hiu tng tn hn v c s l thuyt mch tng t.
- K nng: + S dng thnh tho phn mm Electronics workbench v kim nghim mch trn phn mm ny.
+ Thy r s khc bit gia l thuyt v khi thc hnh trn phn mm ny.
III.Thc Hnh:
Sau khi nm r c cc tnh cht v chn ca cc linh kin th sinh vin bt u vo rp mch.Trong mn thc tp mch tng t ny c th sinh vin phi lm 6 bi thc tp nh sau :
1. Chnh lu in th -Ngun cp in.
2. Phn cc v khuych i Transistor.
3. Khuych i cng sut.
4. Khuych i thut ton.
5. ng dng khuych i thut ton.
6. Mch dao ng.
- Tt c cc bi thc tp ni trn c th hin kh r v c th nh sau :
Bi 1: CHNH LU IN TH -NGUN CP INI. Mc ch: 1. Kho st cc mch chnh lu v lc to ngun in DC. 2. Kho st cc mch n p dung Diode Zener v Transistor
II. C s l thuyt:
n li l thuyt v cc mch chnh lu v lc RC, n p dng Diode Zener v transistor.
Mch n p chuyn i ngun xoay chiu sang mt chiu vi in th ra n nh trong mt khong cho php no .III. Bo co:1.Mch chnh lu bn k v lc RC:a. Khi cha mc t:
Lp mch nh hnh bn, vi:
Ngun: 5V, tn s 1Khz.
in tr: 100 Ohm.
Hnh 1.1
Dng sng ca hnh 1.1
Hnh 1.2: Dng sng ca hnh 1.1.
b. Thay i chiu ca Diode, lp mch nh hnh bn di:
Hnh 1.3: Thay i chiu Diode Quan st dng sng ta thu c hnh bn di:
sng ra
sng vo
Hnh 1.4: Dng sng ca hnh 1.3Nhn xt:
Khi cha thay i chiu Diode:
+ bn k dng Diode c phn cc thun nn dn in. Dng in qua in tr R c tr s bin thin theo bn k dng ca in p li vo.+ bn k m Diode phn cc nguc nn khng dn in, lc ny khng c dng in chy qua Diode
+ Kt qu dng in v in p trn ti ch xut hin bn k dng nn in p ra l in p mt chiu c dng sng nh hnh 1.2. Khi thay i chiu Diode:
+ bn k dng Diode phn cc ngc nn khng dn in, nn khng c dng chy qua Diode.
+ bn k m Diode phn cc thun nn dn in. Dng in qua in tr R c tr s bin thin theo bn k m ca in p li vo.
+ Dng in v in p trn ti ch xut hin bn k m, in p ra l in p mt chiu c dng sng nh hnh 1.4.
( Qua ta rt ra nhn xt:
+ Diode ch dn in khi c phn cc thun.
+ Diode c tc dng chuyn ngun xoay chiu thnh mt chiu.
+ Sng li ra c gn sng cao.
Mc mt Volt k song song vi ti R ta o c gi tr ca R:
VR = 1.888 (V) :Khi cha thay i chiu Diode
VR = -1.891 (V) :Khi thay i chiu Diode
c. Mc mt t C song song vi ti R, c gi tr 10(F:
Lp mch nh hnh v:
Hnh 1.5: Mch chnh lu v lc RC khi mc thm t.Mc mt Volt k song song vi ti R, ta o c in p hai u ti R:
VR = 4.672 (V) Quan st dng sng ta c hnh bn di:
sng ng ra Sng ng vo
Hnh 1.6: Dng sng ca hnh 1.5.
Nhn xt:
Khi mc thm t C, sng ra bng phng hn, t nhp nh hn so vi khi khng mc t.
Sng ra t nhp nh hn l do:
+ bn k dng Diode dn in, dng in i qua t v ti R(in p tng, lc ny t np in.
+ bn k m Diode khng dn in(in p gim t nh v khng, lc ny t phng in qua R b vo s gim in p ra theo thi gian(gim gn sng ca in p mt chiu trn ti.
Dng in qua ti c lin tc v gn sng li ra gim so vi khi khng mc t nh c tnh np x ca t.
d. Gim in tr ti: xung cn 50 Ohm.
Mc Volt k song song vi ti R, ta o c in p hai u ti R:
VR = 3.847(V)
Lp mch nh hnh 1.5, nhng gim in tr ti cn 50 Ohm, quan st dng sng ta c hnh nh bn di: sng ng ra
sng ng vo
Hnh 1.7: Dng sng khi gim in tr ti xung 50.
Nhn xt:
Sng ra nhp nh hn so vi trng hp in tr ti R=100 Ohm, nhng t nhp nh hn so vi khi cha mc t. Do dng x ca t gim dn theo hm s m t I = VDC/R xung 0V.Dng x tnh theo cng thc: ic(t) =
in tr gim (dng ti ln(yu cu t x in nhiu hn(dng x ca t tng( gn sng tng ln.( T cc kt qu trn ta c nhn xt: + Diode c tc dng chuyn ngun in xoay chiu thnh mt chiu. +T in c tc dng lm sng ng ra bng phng hn, gi tr in dung ca t lc cng ln sng ra cng bng phng, gi tr ca in tr cng nh sng ra c gn sng cng cao v ngc li (trng hp c mc t).
+ Gi tr in p trn ti c th o bng Volt k.
2. Chnh lu ton k v lc RC :
a.Mch chnh lu ton k dng 2 Diode:
Lp mch nh hnh v, vi cc gi tr nh sau:
in tr R = 100 Ohm.
T in C = 100 (F.
Ngun xoay chiu: 6 V/50 Hz.
Hnh 2.1: Chnh lu ton k v lc RC.- Dng sng ca mch khi cha mc t, ta nhn c sng c dng nh hnh bn di:
Hnh 2.2: Dng sng ca mch khi cha mc t.
- Khi mc t C vo mch, quan st dng sng ta nhn c sng c dng nh hnh bn di:
Hnh 2.3: Dng sng khi mc t C.- Thay i gi tr ca t C v quan st dng sng:
+ Khi tng gi tr ca t C ln 1000 (F, quan st dng sng ta thu c song c dng nh hinh bn di:
Hnh 2.4: Dng sng khi tng gi tr t C ln 1000 (F.
+ Khi gim gi tr ca t xung cn 50 (F , quan st dng sng ta thu c hnh nh bn di:
Hnh 2.5: Dng sng khi gim gi tr ca t cn 50 (F.
T cc dng sng nhn c cc hnh trn, ta rt ra nhn xt:
+ Khi cha mc t, do Diode c tc dng chnh lu dng xoay chiu thnh dng mt chiu nn sng ra l sng mt chiu nhng sng c gn sng cao(hnh 2.2).
bn k dng Diode D1 dn, nhng Diode D2 khng dn. bn k m Diode D1 khng dn nhng Diode D2 dn ( c hai bn k u c dng chy qua ti nn sng li ra c lin tc. + Khi mc t C c in dung 100 (F, nh c tnh np x ca t in nn sng ng ra c gn sng t hn so vi khi khng mc t (hinh 2.3).
+ Khi tng gi tr ca t ln 1000 (F, nh c tnh np x ca t in dng in qua ti c lin tc v gn sng nh hn khi t c in dung 100 (F (hnh 2.4).
+ Khi gim gi tr ca t in cn 50 (F, sng li ra c gn sng thp hn so vi khi khng mc t nhng cao hn so vi khi t c in dung l 100 (F v 1000 (F (hnh 2.5).( T cc kt qu trn ta rt ra nhn xt:
+ Mch hnh 2.1 l mch chnh lu ton k v hai bn k u c dng chy qua ti. S mch chnh lu hai na chu k s dng Diode chnh l hai s chnh lu mt na chu k mc song song c ti chung.
+ in dung ca t cng tng, kh nng tch in cng cao nn sng ra cng bng phng.
+ in dung ca t cng thp, kh nng tch in cng gim nn sng ra c gn sng cao hn.
b. Mch chnh lu cu:
in tr R = 100 Ohm
T in C = 100 (F.
Ngun xoay chiu 6V/50Hz.
Hnh 2.6: Mch chnh lu cu.
- Khi cha mc t quan st dng sng ta c sng c dng nh hnh bn:
Hnh 2.7: Dng sng khi cha mc t. Khi mc t C, quan st dng sng ta thu c sng c dng nh hnh bn di:
Hnh 2.8: Dng sng khi mc t.- Thay i gi tr ca t C v quan st dng sng:
+ Khi tng gi tr ca t C ln 200 (F, quan st dng sng ta thu c sng c dng nh hnh bn:
Hnh 2.9: Dng sng khi tng gi tr t C ln 1000 (F. + Khi gim gi tr ca t xung cn 50 (F, quan st dng sng ca mch ta thu c sng c dng nh hnh bn:
Hnh 2.10: Dng sng khi gim gi tr t C cn 50 (F.T cc dng sng nhn c hnh 2.7, 2.8, 2.9, 2.10 ta rt ra nhn xt:
+ Ging nh trng hp chnh lu dng hai Diode, sng ra l sng mt chiu, lin tc nhng c gn sng cao.
bn k dng ca chu k: Diode D1 v D3 phn cc thun nn c dng chy trong mch t ngun(D1(R ti(D3(ngun.
bn k m ca chu k: Diode D2 v D4 phn cc thun nn c dng chy trong mch theo chiu t ngun(D2(R ti(D4(ngun.
+ Khi mc thm t C song song vi ti R, nh c tnh np x ca t dng mt chiu ng ra bng phng hn. Khi thay i gi tr in dung ca t ta thy khi gi tr in dung ca t cng ln sng ra cng bng phng.
( So vi mch chnh lu dng hai Diode,trong mch chnh lu cu dng bn Diode do in p ngc t ln mi Diode nh hn nn sng ra c bng phng hn.3. Ngun lng cc i xng:
Mc mch nh hnh v, vi:
in p xoay chiu 6V/50Hz.
Thay i gi tr t C ( 100 (F, 1000 (F).
Hnh 3.1: Ngun lng cc i xng.
Khi t C c in dung C = 100 (F, mc Volt k song song vi ti R nh hnh v o in p li ra: ( VR = 6.381 (V).
Khi t C c in dung C = 1000 (F, mc Volt k song song vi ti R nh hnh ta o c in p li ra c gi tr: ( VR = 7.598(V).
Nhn xt:
+ Khi t c in dung 100 (F ( kh nng tch in thp hn so vi khi t c in dung 1000 (F ( dng x ca t qua R khi C = 100 (F thp hn khi C = 1000 (F (in p trn ti R khi t C = 100 (F c gi tr thp hn khi t C = 1000 (F.4.Mch nhn in p:
Mc mch nh hnh v, vi:
T C1=C2=C3=1000 (F.
Ngun xoay chiu 6V / 50Hz.
in tr R=100Ohm.
Hnh 4.1: Mch nhn i in p c bn.Khi khng gn ti R:
Mc Volt k song song vi t C1, C2, C3, o in p hai u t ta nhn c cc gi tr sau:
VC1=7.269 (V)
VC2=7.270 (V)
VC3=14.54 (V)
Khi c gn ti R:
Mc Volt k song song vi t C3, o in p hai u t (cng chnh l in p trn ti) ta c gi tr sau:
VC3=13.89 (V)
5. Mch n p ni tip:
S hnh di l mch n p ni tip c bn, trong thc t Transistor T1 l Transistor cng sut v cn tn nhit y .
in p xoay chiu 12V / 50Hz.
Bin tr P c in tr 250 Ohm, ti R=200 Ohm.
Khi mch ng c cc h thc:
Vo= Vi VCE1 (1)
Vo= Vz VBE2 VBE1 (2)
Hnh 5.1: Mch n p ni tip c bn.
1. Chnh chit p c gi tr nh hnh v in p li vo Vi ( 8.5 (V), mc Volt k o cc gi tr ca: Vi, VCE1, Vz, VBE2, VBE1. Ta nhn c cc gi tr nh sau:
Vi = 8.526 (V)
VCE1 = 1.612 (V)
Vz = 8.525 (V)
VBE1 = 0.8655 (V)
VBE2 = 0.7461 (V)Thay cc gi tr trn vo hai thc (1) v (2), ta c:
Vo = Vi VCE1 = 8.526-1.612 = 6.914 (V) Vo= Vz VBE2 VBE1 =8.525-0.7461-0.8655 = 6.9134 (V) Gi tr Vo o c l: Vo=6.914 (V).
Qua ta c nhn xt:
So snh Vo khi o vi gi tr Vo nhn c khi thay cc gi tr o c vo h thc (1) v (2) ta thy kt qu nhn c tng i chnh xc. ( Vy mch ng.
2. Xoay chit p h Vi xung xp x 8V, 7V, 6V, 5V, 4V. Mi ln o v ghi ki kt qu Vo, Vi ta c bng bn di:ViVo
8 V6.358 V
7 V5.580 V
6 V4.392 V
5 V3.394 V
4 V2.520 V
3. in th no th h thc (1) khng cn ng na:
Khi xoay chit p cn 7%, Vi = 1.073(V):
Ta o c: VCE1 =1.072(V)
Vo = 422.3((V)
Thay vo h thc (1) ta c:
Vo = Vi VCE1 =1.073-1.072=0.001(V)
So snh gi tr Vo o c vi gi tr Vo tnh ton c khi thay cc gi tr vo h thc (1), ta thy h thc (1) khng cn ng na, hai gi tr lch nhau mt khong 0.001x106(V)-422.3 ((V)=577.7((V).
4. Xoay chit p t Vi ( 8.5 (V); i tr ti thnh 50 Ohm. Kim tra li hai h thc.
Chnh chit p v v tr 85%, Vi = 8.477 (V) ( 8.5 (V), mc Volt k o cc gi tr ca: Vi, VCE1, Vz, VBE2, VBE1. Ta nhn c cc gi tr nh sau:
Vi = 8.477(V)
VCE1 = 1.684(V)
Vz = 8.473 V)
VBE1 = 0.901(V)
VBE2 = 0.7666(V)
Thay cc gi tr trn vo hai h thc (1) v (2), ta c: (1) ( Vo = Vi VCE1 =8.477-1.684 = 6.793(V) (2) ( Vo= Vz VBE2 VBE1 = 8.473-0.7666-0.901=6.8054 (V)
Gi tr Vo o c l: Vo= 6.793(V).
Qua ta thy hai h thc ng.
BI 2: PHN CC V KHUCH I TRANSISTOR.
I.Mc ch:
Phn cc Transistor lng cc (BJT).
Khuch i tn hiu nh.
Phn cc v khuch i JFET.
Phn cc MOSFET.
II. C s l thuyt:
III. Thc hnh:
Transistor c dung trong mch vi ba cu hnh khc nhau: C chung, B chung, E chung vi BJT; S chung, D chung, G chung vi FET v MOSFET. Nhng trong bi ny s tp trung cu hnh ph bin nht ( E chung vi BJT v S chung vi FET< MOSFET).1. Phn cc BJT dung hai ngun cp in:
Mc mch nh hnh v:
Vo trong nhm phn t ngun c: +Vcc ( mc nh +5V )
Bin tr R=250 Ohm.
RB=100 k(
Rc=3.3 k(
Ngun nui 12V.
Ta c:
IB=( VBB - VBE) / RB.
IC=( VC - VCE) / RC.
Hnh : Mch phn cc BJT dng hai ngun cp in. Thay i gi tr ca chit p VCE c cc gi tr xp x t 1V n 11V, mc Volt k v Ampe k o cc gi tr in p v dng in, ta lp c bng bn di:VCE (V)VBB (V)IB (mA)IC (mA)(=IC/IB
1.290(V)4.049(V)33,49(A3.24mA96.91
3.085(V)3.498(V)27.98(A2.7mA96.55
6.010(V)2.599(V)18.99(A1.82mA95.58
6.819(V)2.349(V)16.49(A1.57mA95.21
7.626(V)2.099(V)13.99(A1.33mA94.74
9.707(V)1.450(V)7.5(A0.69mA 92.65
10.95(V)1.050(V)3.5(A0.32mA90.91
Trong cc mch thc thng gn thm in tr RE: l in tr n nh nhit ( lm cho s phn cc transistor t thay i khi nhit ca transistor thay i ). S mch c v nh hnh bn di:
Phn cc BJT dung mt ngun cp in, s mch nh hnh bn di:
2. Khuch i BJT cc pht chung:
Ngun xoay chiu 1 mV, tn s 1 KHz.
in tr RB1 = (68 k( + Bin tr 50 k().
in tr RB2 = 22 k(.
in tr RC = 2.7 k(.
in tr RE = 560(
in tr ti Rt = 4.7 k(.
S mch c dng nh hnh bn di:
Hnh: Khuch i BJT cc pht chung.
a. Khuch i c t r dng CE:
Phn cc cho VCE ( 5V. Mc Oscilloscope ti li vo v li ra, ta thu c sng c dng nh hnh bn di:
Sng li ra
Sng li vo
Bin nh nh ca tn hiu vo:
VppA= 1.4 x 2 (mV) = 2.8 (mV) Bin nh nh ca tn hiu ra:
VppB= 2 x 200 (mV) = 400 (mV)
( li Gt =
EMBED Equation.3 = =142.86.Nhn xt: Sng li vo v li ra u c dng hnh sin v ngc pha nhau. Bin ca sng li vo rt b so vi bin ca sng li ra. Do khuch i in p ln.
b. Khuch i khng c t r dng CE:
B t CE ra khi mch, quan st dng sng li vo v li ra c dng nh hnh bn di: Sng li ra
Sng li vo
Bin nh nh ca sng li vo:
VppA= 1.4 x 2 (mV) = 2.8 (mV)
Bin nh nh ca sng li ra:
VppB= 1.6 x 5 (mV) = 8 (mV)
( li
Nhn xt: Sng li vo v li ra vn c dng hnh sin v ngc pha nhau. Bin ca sng li ra khng thay i, nhng bin ca sng li ra nh hn rt nhiu so vi bin ca sng li ra khi c mc t CE. Do khuch i in p cng gim.
3. Phn cc v khuch i JFET:
Mch phn cc ph bin l phn cc t ng.
Trong mch s dng JFET knh N.
Mch c v nh hnh bn:
Lp bng: ID=VS / RSVGS (mV)VDS (mV)
RS= 1k(29.16 (mA)-291.85.199
RS= 470 (33.87 (mA)-86.064.304
RS= 2K(23.41
(mA)-291.66.374
Thng thng JFET c phn cc sao cho VDS nm trong khong t VDD / 3 n VDD / 2.
VDD = 12 V; RD = 22k(.
Mch khuch i:
V = 12V
C1 = 0.1 (F
Ngun 1 mV, 1 KHz
RG = 1 M
RS = 1 K
Cs = 47 (F
Rt = 10 K
C2 = 22 (F
RD = 22 K
Khi mc Oscilloscope quan st tn
hiu li vo v li ra, sng c dng
nh hnh sau: Sng li ra
Sng li vo
Gi tr nh nh ca in p li vo:
VppA = 1.4 x 2 (mV) = 2.8 (mV)
Gi tr nh nh ca in p li ra:
VppB = 1.3 x 5 (mV) = 6.5 (mV)
( li .4. Phn cc MOSFET ( s lc ):
Mch hnh bn l mt cch phn cc cho
MOSFET loi tng knh N.
V= 12V
RG2= 1M
RS = 1K
RD= 2,7K
VGS = VG - VS
VG =
RG13 M Ohm2 M Ohm1 M Ohm
VG2.978(V)3.974(V)5.970(V)
VS83.75(mV)146.5 (mV)319.3(mV)
ID= VS / RS83.75((A)146.5((A)319.3((A)
VGS2.894(V)3.828(V)5.6507(V)
Dng Volt k o v lp bng:BI 3: KHUCH I CNG SUTI. Mc ch:
Ngi ta phn chia khuch i lm hai loi: khuch i tn hiu nh hay tin khuch i v khuch i tn hiu ln hay khuch i cng sut. Trong h thng m thanh, tn hiu t micro i vo tin khuch i ri qua mt mch x l tn s, tip theo n khuch i cng sut ri ra loa.
C nhiu hng khuch i cng sut v cctransistor c th l BJT hay MOSFET. Trong bi ny ch gii thiu mt s tnh cht ca khuch i cng sut, do nhiu yu t v mch v thc t khng c cp n.
II. C s l thuyt:
- Trong khuch i cng sut, bin in th tn hiu ln cng vi bin dng in tn hiu ln to cng sut tn hiu ra t vi trm mW n vi trm W. Cc transistor tng ra cui cng, v i khi c tng thc k trc, l cc transistor cng sut. Cng sut tiu tn cc transistor ny ln nn chng phi c gii nhit tht hiu qu.
- Da vo s phn cc cho transistor v ch tn hiu, ngi ta chia khuch i cng sut ra nhiu hng: A, B, AB, C, D, E, H. i vi khuch i m thanh, hng AB c dng ph bin nht
III. Thc hnh:
1. Khuch i cng sut hng A: Transistor cng sut c phn cc dn in chu k tn hiu, iu ny lm transistor tiu tn cng sut ln, m gn na l v ch, nn cn gii nhit hiu qu. Tuy nhin khuch i hng A l tuyn tnh, trung thc cao. Khuch i hng A ch c dng cng sut thp (di 10W).
a. Khuch i cng sut hng A khng c ti ring:
in tr Rc = 100 Ohm ng thi l ti. iu chnh bin tr VcQE = (Vcc/2)~6V
+ Khi g b ngun 12V:
Mc Volt k song song vi hai u
in tr RB ( R1 v bin tr ), ta o c :
VRB = 0 (V)
( in p hai u RB l 0V l do khng c ngun cung cp nn khng c dng qua RB.
+ Khi gn li ngun 12V, mc Volt k o
VRC v VBE, ta o c:
VRC = 7.4 (V)
VBE = 883.6 (mV).
Ngun xoay chiu 10mV
R1 = 10K; Bin tr 10K
T 100uF
Tnh :
IBQ = ( Vcc - VBE)/ RB ICQ = VcEQ / RC
= IC / IB
Ta c:
(
M ngun tn hiu sin tn s 1 KHz (bin 10mV ). Ta c dng sng li ra v dng sng li vo nh sau: Sng li ra sng li vo
Gi tr nh nh ca sng ti li vo:
VPPA = 1.4 x 20 (mV) = 28 (mV)
Gi tr nh nh ca sng ti li ra:
VPPB = 1.2 x 5 (V) = 6 (V)
( li Gv = vo / vi = VPPB / VPPA = 6 x 103 / 28 = 214.286 (ln)
Nhn xt: sng ti li vo v li ra u c dang hnh sin v ngc pha nhau. khuch i ln.b. Khuch i cng sut hng A c ti ring:
Lp mch nh hnh bn:
Gn Oscilloscope quan st tn hiu li vo v li ra, v dng sng:
Dng sng thu c: Sng li ra Sng li vo Gi tr nh nh ca sng li vo:
VPPA = 2.8 x 10 (mV) = 28 (mV)
Gi t nh nh ca sng li ra:
VPPB = 3 x 1 (V) = 3 (V)
( li Gv = vo / vi = VPPB / VPPA = 3 x 103 / 28 = 107.143 (ln)
Nhn xt: sng vo v ra u c dng hnh sin va o pha nhau. khuch i khi khng c ti ring ln hn so vi khi c ti ring rt nhiu.
2. Mch khuch i hng B:
Hnh 2a
hnh 2b
khuch i hng B, Transistor khng c phn cc trc. Tn hiu xoay chiu c p vo cc nn ca Transistor. bin dng ca tn hiu Transistor dn, bin tn hiu cng ln th Transistor cng dn mnh. bin m ca tn hiu Transistor ngng dn. Nh vy Transistor ch dn na chuv k dng tn hiu, thc t khi bin tn hiu ln hn khong 0.6V th Transistor mi bt u dn.
Thng ngi ta dng hai Transistor cng sut b nhau: mt NPN v mt PNP nhng c cc c tnh nh (, h s nhit, cng sut,ging nhau.
To l khuch i thc, T1 v T2 l hai Transistor cng sut b nhau. Mch hnh 2a dng ngun cp in n Vcc nn in th ti im M l Vcc/2 do phi c t C cch ly dng in mt chiu. Cn mch hnh 2b dng ngun cp in i xng nn in th ti im M l 0V v ti c gn trc tip.
Trong mch hnh 2b, khi tn hiu trong khong t -0.6V n +0.6V ( in th ngng Transistor) khng c Transistor no dn nn tn hiu ra bng khng. S mt tn hiu ny to nn mo dng xuyn qua. Tn hiu vo c bin nh nh cng ln th s mo dang xuyn qua cng tr nn khng ng k.
3. Khuch i cng sut hng AB:
Khuch i hng AB l khuch i dung ha gia hng A v hng B. Lc by gi hai Transistor cng sut c phn cc va chm dn in ( VBE ( 0.6V ) khi c tn hiu l dn ngay, do trnh c hin tng mo dng xuyn qua.
Hnh: Mch khuch i cng sut hng AB.
Ngun tn hiu vo: 10 mV, 1 KHz.
T C1: 20 (F
C2: 200 (F
C3: 47 (F
in tr Rb1=Rb2=560 Ohm R3=R4=1 Ohm
R5=R6=4.7 k Ohm
RL=8 Ohm
Ngun nui +12 V
Mc mch nh hnh v trn nhng cha gn t C3 ( t Bootstrap ), mc Oscilloscope vo ng ra (trc tr ti RL). Tng bin in p tn hiu vo n khi thy c mo dng hoc b xn gn hai nh ca tn hiu ra. Sng c dng nh hnh bn di:
Mc t C3 vo mch nh hnh v, quan st tn hiu ra, sng c dng:
Nhn xt: Khi tng bin in p tn hiu vo ti 20mV th bt u c s mo dng, tn hiu li vo cng ln th s mo dng cng r rt. Sng li ra khi c gn t C3 c gi tr nh nh ln hn gi tr nh nh khi khng gn t C3Transistor Darlington:
Mt vn kh khn trong khuch i cng sut l phi cung cp dng tn hiu cho cc Transistor cng sut khi tn hiu vo ln. Ngoi cch dng t Bootstrap nh trn cn cn c nhng cch khc. Thng thng Transistor Darlington c dng thay cho Transistor n. Transistor darlington c th l loi tch hp hoc t lp ri. hai transistor mc darlington ging nh mt transistor c h s khuch i dng ( = (1 x (2.
Do ( c th n vi ngn, v c th khin mch khng n nh nn cn thm in tr v gi cho ( mc va phi.
C rt nhiu IC khuch i cng sut m thanh trn
th trng c cng sut tn hiu t di 1W n trn 100W
hiu dng . cc IC ny c cu trc mch bn trong rt phc
tp so vi cc mch ri kho st.
V d: D2822N, AN7130
AN7130 c 17 transistor, 6 Diode v trn 20 in tr
t, gn ngoi h tr thm 10 tr, t dng ngun 18V, cng
sut 10W, dng 3A.
BI 4: KHUCH I THUT TON I. Mc ch:
Khuch i thut ton (Operational Amplifer - OPAMP) l khuch i tnh ton (cng, tr, tch phn). y l ngha v cng dng ban u, ngy nay ngi ta xem khuch i thut ton nh mt mch in t a nng: khuch i, lc tn s, so snh, to dao ng, lm ton. KTT theo ngha thng thng l cc mch tch hp v i khi c gi l cc mch tch hp tuyn tnh.
II. C s l thuyt:
Khuch i thut ton ( KTT ) c hai ng vo, gi l ng vo (-) hay o v ng vo ( + ) hay khng o. Mt ng ra ( i khi hai ng ra o pha nhau ), v c hai ng cp in mt chiu i xng. Tn hiu vo c p gia hai ng vo hoc gia mt ng vo v t.
KTT l mch tch hp gm khong v chc transistor v nhiu diode, tr, t, to nn cc mch : khuch i vi sai u vo, ngun dng, mch chuyn mc in th, khuch i ra khuch i vi sai, transistor lng cc (BJT) hoc JFET,MOSFET c th c dng, sau ch yu l BJT, nhng cng c KTT gm ton MOSFET.
Cc c tnh c bn ca KTT l:
C th khuch i tn hiu mt chiu v xoay chiu
li vi sai vng h (vo/vi) rt ln, trn 100000 ln ( l tng v cng)
Tr khng ng vo ri rt ln, trn 1m Ohm( l tng v cng )
Tr khng ng ra ro rt nh, di 100 Ohm ( l tng l 0 )
III. Thc hnh:
1. Khuch i vi sai dng transistor ri:
Khuch i vi sai cn gi l khuch i hiu s la tng u tin ca cu trc KTT, quyt nh nhiu c tnh k thut ca KTT. Do d hiu KTT th nn bit qua khuch i vi sai. ( Gi tr mc nh Vcc trong phn mm l +5V)
Trn hnh l khuch i vi sai c bn. Trong mch s dng hai transistor ging ht nhau, in tr Rc1 = Rc2 = 10K, in tr RE = 20K; ngun +Vcc = 5V v ngun i xng +-12V
Chnh chit p P V1=0V v V2 ln lt l cc gi tr xp x 0V; 0,1V; 0,2V; 0,3V ri lp bng :
V1 V20 V-0,1V-0,2V-0,3V
Vc1 Vc29.122-9.122 =0V11.77-6.437= 5.333V11.88-6.276= 5.604V11.88-6.225= 5.655V
Gvd0-53.33-28.02-18.85
Vi Gvd = (Vc1 Vc2)/( V1 V2).
2. Khuch i DC v AC c bn:
Khuch i thut ton ph bin nht uA741, n c c tnh k thut mc trung bnh nhng ph bin v c t lu trn th trng, gi r, tt cho phn ln cc ng dng thng thng.
Chc nng c bn l khuch i tn hiu t tn s khng (khuch i DC) ln vi chc KHz v hn (khuch i AC).
* uA741 c 8 chn:
Chn 1 v chn 5 : chnh 0 offset
Chn 2 : li vo ( - )
Chn 3 : li vo ( + )
Chn 4 : cp ngun Vdd ( thng thng -12V ) Chn 6 : li ra
Chn 7 : cp ngun +Vdd ( thng thng + 12V ) Chn 8 : b trng
a. Khuch i dc o v khng o:
Trong m phng ch s dng nhng chn cn thit v th KTT s khng c 8 chn
Lp mch nh hnh v:
Thay i chit p Vi~5mV
t R1 = 1K
Gv = Vo / Vi
Gv = - R2 / R1 Thay i R2 v lp bngR21K10K100K1M
Gv-1-10-100-1000
Gv-1-10-100-1000
Cho R2 = 10K. Thay i chit p c cc gi tr xp x nh sau:
Vi~5mV~20mV~100mV~0.5V
Vo-50,71mV-207mV-978,4mV-4,537V
Gv-10,142-10,35-9,784-9,074
Hnh bn l s mch khuch i khng o, li l thuyt Gv = 1+ (R2/R1)
iu chnh chit p sao cho Vi~50mV
*in tr R1=1K
Lp bng R21K10K100K1M
Gv211100.98400
Gv2111011001
Vi
Cho R2 = 10K, lp bng.Vi(50mV(100mV(150mV(500mV
Vo0.55V1.1V1.65V5.5V
Gv11111111
So snh kt qu hai mch khuch i o v khng o, nhn xt:
- Mch khuch i dc o th Gv v Gv m
- Mch khuch i dc khng o Gv v Gv dng
b. Khuch i AC o v khng o:
cc khuch i tn hiu xoay chiu, phi thm t in ng vo v ra ngn dng in mt chiu. Cc t ny phi c dung khng nh so vi cc in tr ni tip lin quan.
* Mc mch khuch i AC o:
Ngun tn hiu sin 50mV, tn s 1KHz
in tr R2 = 100K
R1 = 10K
T in C1 = 1uF
C2 = 10uF
Sng li ra sng li vo
Gi tr nh nh ca tn hiu li vo:
VPPA = 2.8 x 50 (mV) = 140 (mV) Gi tr nh nh ca tn hiu li ra:
VPPB = 1.7 x 2 (V) = 3.4 (V)
li Gv = -vo / vi = -VPPB / VPPA = -24.286 (ln)
Du - c ngha tn li vo v ra o pha nhau.
Nhn xt: mch khuch i o c sng li vo v ra dng hnh sin.
Tn hiu li vo v ra o pha nhau.
Mc mch khuch i AC khng o:
Ngun tn hiu sin 50mV, tn s 1KHz
in tr R2 = 100K
R1 = 10K
T in C2 = 10uF
Mc Osilloscope quan st vi v vo
Cp in cho mch, quan st tn hiu
V li dng sng vo ra, tnh li?.
Sng li vo sng li ra
Gi tr nh nh ca tn hiu li vo:
VPPA = 2.8 x 50 (mV) = 140 (mV)
Gi t nh nh ca tn hiu li ra :
VPPB = 1.7 x 2 (V) = 3.4 (V)
li Gv = vo / vi = VPPB / VPPA = 24.286 (ln)
Nhn xt: Mch khuch i khng o c sng li vo va ra dng hnh sin. Tn hiu li vo v ra cng pha. khuch i in p ca mch khuch i AC o v khng o ging nhau.BI 5: NG DNG KHUCH I THUT TONI. Mc ch:
Kho st mt s mch ng dng tiu biu ca KTT nh mch khuch i vi sai, mch cng tr, mch ly tch phn.
II. Thc hnh:
1. Khuch i vi sai ( khuch i hiu s ):Do c tnh ca KTT c hai ng vo nn c th s dng KTT khuch i s sai bit ca hai tn hiu vo.
Khuch i vi sai c bn :
Chn R1 = 1K, R2 = 10 K
Vi s mch nh hnh bn :
( Vo Vi2) = -R2/R1(Vi1 Vi2)
t gi tr chit p P ti Vi1 l 50%
Thay i chit p P ti Vi2 theo bng:
Hnh 5.1
Lp bng:
P (Vi2)0%5%10%15%20%
Vi1- Vi22V1,8V1,6V1,4V1.2V
Vo - Vi2-20V-18V-16V-14V-12V
Vo-20V-17,75V-15,5V-13,25V-11V
2. Mch lm ton:
a. Mch cng v mch tr:Mch cng c s nh hnh 2a, tnh ton l thuyt:
EMBED Equation.3 t R1 = 1K
R2 = 2K
RF = 1K.
Cho V1 = 5V, V2 = 5V. o Vo = -7,5V Hnh 2a Tnh ton l thuyt:
Cho V1 = 5V, V2 = -5V. o Vo = -2,5V
Tnh ton l thuyt:
Mch tr c s nh hnh 2b:
Tnh ton l thuyt:
t R1 = 1K, RF = 2,2K
R2 = 10K, R3 = 10 K
Cho V1 = 5V, V2 = 5V. o Vo = -3V
Tnh ton l thuyt:
hnh 2bCho V1 = 5V, V2 = -5V. o Vo = -19V
Tnh ton l thuyt:
b. Mch t hp:
Mch t hp c s nh hnh 2c:
Hnh 2c
t V2 = 12V Cho R1 = R3 = R4 = R5 = 10K
R2 = 22K; R6 = 5,6K
o in p li ra v so snh vi l thuyt Vo = 1,526V
c. Mch tch phn:
Lp mch nh hnh bn :
in tr 1K
T in 2,2uF
i vi mch tch phn ta chn:
Tn hiu vo l xung vung vo(t) Frequency 100Hz Duty cycle 50%
Amplitude 5V
Offset 0
Chnh cc thng s trn Oscilloscope cho ph hp;
Quan st tn hiu, sng c dng nh hnh bn di:
BI 6:MCH DAO NGI. Muc ch:
Khao sat mot so mach dao ong pho bien va s dung phan mem CrocPhys e mo phong.
Cu the trong bai nay se khao sat cac mach sau:
- Mach dao ong a hai
- Mach n hai
- Mach tao song sin
II. C s ly thuyet:
Mach dao ong la mach t no thay oi trang thai mot cach tuan hoan e tao ra tn hieu
loi ra co the co dang xung vuong hay sin. Tuy nhien mot so mach cung c goi la dao ong
mac du phai c kch thch t ben ngoai.
Cc mch dao ng iu ho thng c dng trong cc h thng thng tin,trong cc my o ,trong my kim tra..,Cc mch dao ng c th lm vic tt trong di tn t vi Hz cho n hng nghn MHz.
to dao ng c th dng cc phn t tch cc nh: n in t, transistor lng cc (BJT),transistor thng (FET),cc b khuych i thut ton
phm vi tn s thp v trung bnh ngi ta thng dng khuych i thut ton,cn phm vi tn s cao v rt cao th dng transistor lng cc v transistor thng hoc cc loi diode c bit.
Cc tham s c bn ca mch dao ng gm:tn s ca tn hiu ra,bin in p ra, n nh tn s,cng sut ra v hiu sut.
C th to dao ng iu ho theo hai nguyn tc c bn sau:
_To dao ng bng b khuych i c hi tip dng.
_To dao ng bng phng php tng hp mch.III.Thc hnh
1. Mach dao ong a hai:
Lap mach nh s o:
Vcc = 9V
Rc1 = Rc2 = 560 Ohm , C1 = C2 = 47uF
Ro1= Ro2 = 330 Ohm , RB1 = RB2 = 33 K
Hnh 6.1a y l mch dao ng theo ng ngha: Mch t ng lun chuyn tun hon gia hai trng thi:trng thi T1 dn,T2 ngng v trng thi T1 ngng ,T2 dn.Mch to ra hai tn hiu vung o pha nhau ng ra (gn in tr Ro1,Ro2 v hai n Led)
Mc volt k o,ta c cc in th :
VCE1 = 93.7 (mV) . VCE2 = 93.6 (mV)
VBE1 = 695 (mV). VBE2 = 695 (mV)
Nhn xt: Trng thi cn bng ca mch (mt transistor m,mt trasistor kho )ch n nh trong mt thi gian hn ch no ,ri t ng lt sang trng thi kia,v ngc li.Hai trng thi nu trn ca mch a hi t dao ng cn c gi l cc trng thi chun cn bng.Nhng thay i ca in p v dng in gia cc im trong s dn n mt trng thi ti hn no ,c chu k gn bng nhng nh hn chu k ca in p t dao ng,qu trnh s xy ra sm hn,tng ng lc ta c ch lm vic ng b ca a hi t dao ng. in p tc ng vo(c bin v cc tnh thch hp)gi l in p ng b.
Khi cha thay i gi tr ca t in,ta c th nh bn di
Hnh 6.1b Thay i gi tr ca t C ta c th nhn xt: to ra cc xung c tn s thp hn 1000Hz,gi tr ca t C1,C2 phi ln,cn to ra cc xung c tn s cao hn 10kHz do nh hng qun tnh ca transistor lm gim cht lng ca xung vung.Do , to ra xung vung vng tn s thp v cao ngi ta s dng khuych i thut ton
Thay oi gia tr tu C1 bang 1/2 gia tr tu C2, ta c th nh bn di
Hnh 6.1c khi ta thay i ga tr t C1 bng C2
Khi thay i gi tr C1 bng gi tr C2, ta thy sng ra transistor T1 b thay i,xung ra ca T1 lc ny ch bng so vi lc cha thay i C1.
2. Mach dao ong a hai n on( n hai):
Mach ch co mot trang thai on nh ( ben). Khi c kch t ben ngoai, mach thay oi sang trang thai khac mot cach tam thi roi t ong quay ve trang thai on nh.
Cong dung cua mach la tao ra xung vuong co o rong nhat nh moi khi co kch thch t ngoai mach.
Mac mach nh hnh di vi cac thong so nh sau:
Vcc = 12V
Vd = 5V
C = 47uF
Rc1 = Rc2 = 560 Ohm
Rb1 = 10K
Rb2 = 56K
Rb1 = 4,7K
R1 = 1K; R2 = 5,6K; R3 = 330 Ohm
Hnh 6.2a
Chu y cong tac K, ban au phai trang thai m ( LED khong sang) , dung chuot kch oi vao cong tac e tao ra mot xung am ngan. Quan sat en LED va trang thai cua mach.
Nhn xt
Thay oi thi gian ong/m cong tac K ( thay oi toc o kch oi chuot),ta thy thi gian n LED sng thay i.Lc u n nhp nhy chm hn,nhng sau n ngy mt nhp nhy nhiu hn.
Di y l dng sng ca n khi ta thay i tc kch i chut vo cng tc K
Hnh 6.2b
3. Dao ong sin:
Dao ong cau Wien la mot mach kha thong dung trong viec tao song sin v tnh on nh .Mch dao ng cu wien l mch dao ng trong vng tn s thp n trung bnh,tc l khong 5Hz n 1MHz .Chng c ng dng trong cc my pht m tn thng mi v cc ng dng tn s thp.Cong thc ly thuyet T = 2RwCw at R1 = 10K
R2 = 18K
R3 = 5,6K
Rw = 10K
Cw = 22uF
Hnh 6.3a
Di y l dng sng ca hnh 6.3a
Hnh 6.3b
Nhn xt:Tc dng ca hai diode mc ngc chiu nhau song song vi R3 l: c s dng nh phn t phi tuyn hn ch bin dao ng.Nu b i 1 trong 2 diode trn th bin dao ng lc ny s ln hn bin khi cn c c 2 diode.
EMBED Equation.3
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