Giao Trinh Dien Tu Co Ban MBDMTf9Rhe 20130125021115 617

7/26/2019 Giao Trinh Dien Tu Co Ban MBDMTf9Rhe 20130125021115 617

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Gio Trnh

in t c bn


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MCLC

BI 1: NGUN MT CHIU

BI 2: INTTRNGBI 3: NGUNXOAY CHIU

BI 4: NGHVNNNG

BI 5: INTR- TIN

BI 6: CUNDY - BINP

BI 7: I T TRANSISTOR

BI 8: MCHKHUCHI

BI 9: MCHNP NGUN

BI 10: MCHTODAO NGBI 11: MOSFET THYRISTOR


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BI 1NGUN MT CHIU

I - KHI NIM C BN V DNG IN

1. Cu trc nguyn t :

Tt c cc nguyn t u c cu to ln t cc nguyn t v minguyn t ca mt cht

cu to bi hai phn l

- Mt ht nhn gia cc ht mang in tch dng gi l Proton v cc ht trung ho in g

l Neutron.

- Cc Electron (in t ) mang in tch m chuyn ng xung quanh ht nhn .

- Bnh thng cc nguyn t c trng thi trung ho v in ngha l s Proton ht nhn bng

electron bn ngoi nhng khi c tc nhn bn ngoi nh p xut, nhit , ma st tnh in, t

ng ca t trng .. th cc in t electron lp ngoi cng c th tch khi qu o tr

thnh cc in t t do.

- Khi mt nguyn t b mt i mt hay nhiu in t, chng b thiu in t v tr thnh iondng v ngc li khi mt nguyn t nhn thm mt hay nhiu in t th chng tr thnh ion

m.

2 . Bn cht dng in v chiu dng in .

Khi cc in t tp trung vi mt cao chng to ln hiu ng tch in

- Dng in chnh l dng chuyn ng ca cc ht mang in nh in t , ion.

- Chiu dng in c quy c i t dng sang m ( ngc vi chiu chuyn ng ca cc

in t - i t m sang dng )

3. Tc dng ca dng in :

Khi c mt dng in chy qua dy dn in nh th nghim sau :


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Ta thy rng dng in to ra mt t trng xung quanh lm lch hng ca nam chm,

khi i chiu dng in th t trng cng i hng => lm nam chm lch theo hng ng

li.

- Dng in chy qua bng n lm bng n pht sng v sinhnhit nng

- Dng in chy qua ng c lm quay ng c quay sinh ra c nng

- Khi ta np c quy cc cc ca c quy b bin i v dng in c tc dng ho nng..

Nh vy dng in c cc tc dng l tc dng v nhit , tcdng v c nng , tc dng v t

trng v tc dng v ho nng.

II- DNG IN V IN P MT CHIU.

1. Cng dng in :

L i lng c trng cho mnh yu ca dng in hay c trng cho s lng cc in t

qua tit din ca vt dn trongmt n v thi gian

K hiu l I

- Dng in mt chiu l dng chuyn ng theo mt hng nht nh t dng sang m theo

quy c hay l dng chuyn ng theo mt hng ca cc in t t do.

n v ca cng dng in l Ampe

n v

Kilo Ampe = 1000 Ampe


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Mega Ampe = 1000.000 Ampe

Mili Ampe = 1/1000 Ampe

Micro Ampe = 1/1000.000 Ampe

2. in p :

Khi mt cc in t tp trung khng u ti hai im A v B nu ta ni mt dy dn t A s

B s xut hin dng chuyn ng ca cc in tch t ni c mt cao sang ni c mt th

nh vy ngi ta gi hai im A v B c chnh lch v in p v p chnh lch chnh l hiu

th.

- in p ti im A gi l UA

- in p ti im B gi l UB.

- Chnh lch in p gia hai im A v B gi l hiu in th UAB

UAB

= UA

- UB- n v ca in p l Vol k hiu l U hoc E,

n v in p

Kilo Vol ( KV) = 1000 Vol

Mini Vol (mV) = 1/1000 Vol

Micro Vol = 1/1000.000 Vol

in p c th v nh cao ca mt bnh nc, nu hai bnh nc c cao khc nhau th k

ni mt ng dn s c dng nc chy qua t bnh cao sang bnh thp hn, khi hai bnh nc c

cao bng nhau th khng c dng nc chy qua ng dn. Dng in cng nh vy nu hai im

c in p chn lch s sinh ra dng in chy qua dy dn ni vi hai im t in p cao

sang in p thp v nu hai im c in p bng nhau th dng in trong dy dn s = 0

III- MT S NH LUT C BN

1. nh lut m


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Cng dng in trong mt on mch t l thun vi in p hai u on mch v

t l nghch vi in tr ca on mch .

Cng thc : I = U / R

Trong

I l cng dng in , tnh bng Ampe (A)

U l in p hai u on mch , tnh bng Vol (V)

R l in tr ca on mch , tnh bng m

2. nh lut m cho on mch

2.1-on mch mc ni tip:

Trong mt on mch c nhiu in tr mc ni tip th in p hai u on mch bng

tng st p trn cc in tr .

Theo s trn th : U = U1 + U2 + U3

Theo nh lut m ta li c U1 =I1 x R1 , U2 = I2 x R2,

U3 = I3 x R3 nhng on mch mc ni tip th I1 = I2 = I3

St p trn cc in tr => t l thun vi cc in tr .

2.2on mch mc song song

Trong on mch c nhiu in tr mc song song th cng dng in chnh bng

tng cc dng in i qua cc in tr v st p trn cc in tr l nh nhau:


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Mch trn c U1 = U2 = U3 = E

I = I1 + I2 + I3 v U1 = I1 x R1 = I2 x R2 = I3 x R3

Cng dng in t l nghch vi in tr .

3. in nng v cng xut :

3.1-in nng.

Khi dng in chy qua cc thit b nh bng n => lm bng n sng, chy qua ng c

=> lm ng c quay nh vy dng in sinh ra cng. Cng ca dng in gi l in nn

k hiu l W, trong thc t ta thng dng Wh, KWh ( Kilo wat gi)

Cng thc tnh in nng l :

W = U x I x t

Trong W l in nng tnh bng June (J)

U l in p tnh bng Vol (V)

I l dng in tnh bng Ampe (A)

t l thi gian tnh bng giy (s)

3.2- Cng xut .

Cng xut ca dng in l in nng tiu th trongmt giy , cng xut c tnh bi cn

thc

P = W / t = (U. I .t ) / t = U .I

Theo nh lut m ta c P = U.I = U2 / R = R.I2


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BI 2:

IN T TRNG

I. Khi nim v t trng.

* Nam chm v t tnh .Trong t nhin c mt s cht cth ht c st gi l nam chm t nhin.Trong cng nghipngi ta luyn thp hoc hp cht thp to thnh nam chm nhn to

Nam chm lun lun c hai cc l cc bc North (N) v cc nam South (S) , nu cht thanhnam chm ra lm 2 th ta li c hai nam chm mi cng c hai cc N v S - l nam chmc tnh cht khng phn chia..

Nam chm thng c ng dng sn xut loa in ng, micro hoc m t DC.

* T trngT trng l vng khng gian xung quanh nam chm c tnh cht truyn lc t ln cc vt

liu c t tnh, t trng l tp hp ca cc ng sc i t Bc n cc nam.

* Cng t trngL i lng c trng cho mnh yu ca t trng, k hiu l H n v l A/m


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* t cmL i lng c trng cho vt c t tnh chu tc ng ca t trng, t cm ph thuc

vo vt liu .

VD St c t cm mnh hn ng nhiu ln .

t cm c tnh bi cng thc

B = .H

Trong B : l t cm : l t thmH : l cng t trng

* T thngL s ng sc i qua mt n v din tch, t thng t l thut vi cng t trng.

* ng dng ca Nam chm vnh cu.Nam chm vnh cu c ng dng nhiu trong thit b in t, chng c dng sn xu

Loa, Micro v cc loi M t DC.

Loa

II - T TRNG CA DNG IN

1. T trng ca dng in i qua dy dn thng.


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Th nghim trn cho thy, khi cng tc bn ngoi ng, dng in i qua bng n lmbng n sng ng thi dng in i qua dy dn sinh ra t trng lm lch hng kim namchm .

Khi i chiu dng in, ta thy kim nam chm lch theo hng ngc li , nh vy dngin i chiu s to ra t trng cng i chiu.

2. T trng ca dng in i qua cun dy.

- Khi ta cho dng in chy qua cun dy, trong lng cun dy xut hin t trng l cc

ng sc song song, nu li cun dy c thay bng li thp th t trng tp trung trn

li thp v li thp tr thnh mt chic nam chm in, nu ta i chiu dng in th t

trng cng i hng

- Dng in mt chiu c nh i qua cun dy s to ra t trng c nh, dng in bini i qua cun dy s to ra t trng bin thin.

- T trng bin thin c c im l s to ra in p cm ng trn cc cun dy t trong

vng nh hng ca t trng , t trng c nh khng c c im trn.


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ng dng:

T trng do cun dy sinh ra c rt nhiu ng dng trong thc t, mt ng dng m ta

thng gp trong thit b in t l R le in t.

R le in t

Khi cho dng in chy qua cun dy, li cun dy tr thnh mt nam chm in ht thanh

st v cng tc oc ng li, tc dng ca r le l dng mt dng in nh iu khin

ng mch cho dng in ln gp nhiu ln.

3. Lc in t

Nu c mt dy dn t trong mt t trng, khi cho dng in chy qua th dy dn c

mt lc y => l lc in t, nu dy dn t do chng s chuyn ng trong t trng

nguyn l ny c ng dng khi sn xut loa in ng.


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Nguyn l hot ng ca Loa ( Speaker )

Cun dy c gn vi mng loa v t trong t trng mnh gia 2 cc ca nam chm , c

S l li , cc N l phn xung quanh, khi cho dng in xoay chiu chy qua cun dy , di

tc dng ca lc in t cun dy s chuyn ng, tc ng chuyn ng ca cun dy phthuc vo tn s ca dng in xoay chiu, cun dy chuyn ng c gng vo mng loa

lm mng loa chuyn ng theo, nu chuyn ng tn s > 20 Hz chng s to ra sng m

tn trong di tn s tai ngi nghe c.

4. Cm ng in t .

Cm ng in t l hin tng xut hin in p cm ng ca cun dy c t trong m

t trng bin thin.

V d : mt cun dy qun quanh mt li thp , khi cho dng in xoay chiu chay qua,trn li thp xut hin mt t trng bin thin, nu ta qun mt cun dy khc ln cng li

thp th hai u cun dy mi s xut hin in p cm ng. Bn thn cun dy c dng in

chy qua cng sinh ra in p cm ng v c chiu ngc vi chiu dng in i vo

BI 3:

NGUN XOAY CHIU


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1. Dng in xoay chiu :Dng in xoay chiu l dng in c chiu v gi tr bin i theo thi gian, nhng

thay i ny thng tun hon theo mt chu k nht nh.

trn l cc dng in xoay chiu hnh sin, xung vung v xung nhn.

Chu k v tn s ca dng in xoay chiu.Chu k ca dng in xoay chiu k hiu l T l khong thi gian m in xoay chiu

lp liv tr c , chu k c tnh bng giy (s)Tn s in xoay chiu : l s ln lp li trang thi c ca dng in xoay chiu trong

mt giy k hiu l F n v l Hz

F = 1 / TPha ca dng in xoay chiu :

Ni n pha ca dng xoay chiu ta thng ni ti s so snh gia 2 dng in xoaychiu c cng tn s .

* Hai dng in xoay chiu cng pha l hai dng in c cc thi im in p cngtng v cng gim nh nhau:

Hai dng in xoay chiu cng pha

* Hai dng in xoay chiu lch pha : l hai dng in c cc thi im in p tng


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gim lch nhau .

Hai dng in xoay chiu lch pha

* Hai dng in xoay chiu ngc pha : l hai dng in lch pha 180 , khi dngin ny tng th dng in kia gim v ngc li.

Hai dng in xoay chiu ngc pha

Bin ca dng in xoay chiuBin ca dng xoay chiu l gi tr in p nh ca dng in.xoay chiu, bin

ny thng cao hn in p m ta o c t cc ng h

Gi tr hiu dng ca dng in xoay chiuThng l gi tr o c t cc ng h v cng l gi tr in p c ghi trn zc

cm ngun ca cc thit b in t., V d ngun 220V AC m ta ang s dng chnh lch gi tr hiu dng, thc t bin nh ca in p 220V AC khong 220V x 1,4 ln =khong 300V

Cng xut ca dng in xoay chiu .Cng xut dng in xoay chiu ph thuc vo cng , in p v lch pha gia

hai i lng trn , cng xut c tnh bi cng thc :

P = U.I.cos

Trong U : l in p

I l dng in

l gc lch pha gia U v I


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=> Nu dng xoay chiu i qua in tr th lch pha ga U v I l = 0 khi cos = 1 v P = U.I

=> Nu dng xoay chiu i qua cun dy hoc t in th lch pha gia U v I l+90 hoc -90, khi cos = 0 v P = 0 ( cng xut ca dng in xoay chiu khii qua t in hoc cun dy l = 0 )


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Ch nghin cu: Dng xoay chiu qua tr thun, qua t in, qua cun dy, khi nimv dung khng ca t in v cm khng ca cun dy, tng hp hai dng in xoay chiu.

II -DNG XOAY CHIU QUA R,L,C


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1. Dng in xoay chiu i qua in tr

Dng in xoay chiu i quain tr th dng in v in p cng pha vi nhau , ngha

l khi in p tng cc i th dng in qua tr cng tng cc i. nh vy dng xoay

chiu c tnh cht nh dng mt chiu khi i qua tr thun.do c th p dng cc cng

thc ca dng mt chiu cho dng xoay chiu i qua in tr

I = U / R hay R = U/I Cng thc nh lut ohm

P = U.I Cng thc tnh cng xut

2 . Dng in xoay chiu i qua t in .

Dng in xoay chiu i qua t in th dng in s sm pha hn in p 90

Dng xoay chiu c dng in sm

pha hn in p 90 khi i qua t

* Dng xoay chiu i qua t s b t cn li vi mt tr khng gi l Zc, v Zc c tnhbi cng thc

Zc = 1/ ( 2 x 3,14 x F x C )

Trong Zc l dung khng ( n v l Ohm )

F l tn s dng in xoay chiu ( n v l Hz)

C l in dung ca t in ( n v l Fara)

Cng thc trn cho thy dung khng ca t in t l nghch vi tn s dng xoay chiu

(ngha l tn s cng cao cng i qua t d dng) v t l nghc vi in dung ca t ( ngha

l t c in dung cng ln th dng xoay chiu i qua cng d dng)

=> Dng mt chiu l dng c tn s F = 0 do Zc = v vy dng mt chiu khng i


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qua c t.

3. Dng in xoay chiu i qua cun dy.

Khi dng in xoay chiu i qua cun dy s to ra t trng bin thin v t trng bin

thin ny li cm ng ln chnh cun dy mt in p cm ng c chiu ngc li , do

cun dy c xu hng chng li dng in xoay chiu khi i qua n, s chng li ny chnh

l cm khng ca cun dy k hiu l ZL

ZL = 2 x 3,14 x F x L

Trong ZL l cm khng ( n v l Ohm)

L l h s t cm ca cun dy ( n v l Henry) L ph thuc vo s vng dy qun v

cht liu li .

F l tn s dng in xoay chiu ( n v l Hz)

T cng thc trn ta thy, cm khng ca cun dy t l thun vi tn s v h s t cm

ca cun dy, tn s cng cao th i qua cun dy cng kh khn => tnh cht ny ca cun

dy ngc vi t in.

=> Vi dng mt chiu th ZL ca cun dy = 0 ohm, d dng mt chiu i qua cun

dy ch chu tc dng ca in tr thun R m thi ( tr thun ca cun dy l in tr o

c bng ng h vn nng ), nu tr thun ca cun dy kh nh th dng mt chiu quacun dy s b on mch.

* Dng in xoay chiu i qua cun dy th dng in b chm pha so vi in p 90

ngha l in p tng nhanh hn dng in khi qua cun dy .

Dng xoay chiu c dng in chm

pha hn in p 90 khi i qua cun dy


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=>> Do tnh cht lch pha gia dng in v in p khi i qua t in v cun dy, nn ta

khng p dng c nh lut Ohm vo mch in xoay chiu khi c s tham gia ca L v C

c.

=>> V cng xut th dng xoay chiu khng sinh cng khi chng i qua L v C mc d c

U > 0 v I >0.

4. Tng hp hai dng in xoay chiu trn cng mt mch in

* Trn cng mt mch in , nu xut hin hai dng in xoay chiu cng pha th bin

in p s bng tng hai in p thnh phn.

Hai dng in cng pha bin s tng.

* Nu trn cng mt mch in , nu xut hin hai dng in xoay chiu ngc pha thbin in p s bng hiu hai in p thnh phn.

Hai dng in ngc pha, bin gim


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2


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2

BI 4:

HNG DN S DNG NG H VN NNG

1. Gii thiu v ng h vn nng ( VOM)

ng h vn nng ( VOM ) l thit b o khng th thiu c vi bt k mt k thut vinin t no, ng h vn nng c 4 chc nng chnh l o in tr, o in p DC, o in pAC v o dng in.

u im ca ng h l o nhanh, kim tra c nhiu loi linh kin, thy c s phngnp ca t in , tuy nhin ng h ny c hn ch v chnh xc v c tr khng thpkhong 20K/Vol do vy khi o vo cc mch cho dng thp chng b st p.

2. Hngdn o in p xoay chiu.

S dng ng h vn nng o p AC


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Khi o in p xoay chiu ta chuyn thang o v cc thang AC, thang AC cao hn ip cn o mt nc, V d nu o in p AC220V ta thang AC 250V, nu ta thang thphn in p cn o th ng h bo kch kim, nu thanh qu cao th kim bo thiu chnhxc.

* Ch - ch :

Tuyt i khng thang o in tr hay thang o dng in khi o vo in p xoay chi=> Nu nhm ng h s b hng ngay lp tc !

nhm thang o dng in, o vongun AC => s hng ng h

nhm thang o in tr, o vo ngun AC=> s hng cc in tr trong ng h


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* Nu thang o p DC m o vo ngun AC th kim ng h khng bo , nhng ng hkhng nh hng .

thang DC o p AC ng h khng ln kimtuy nhin ng h khng hng

3. Hng dn o in p mt chiu DC bng ng h vn nng.

Khi o in p mt chiu DC, ta nh chuyn thang o v thang DC, khi o ta t que vo cc dng (+) ngun, que en vo cc m (-) ngun, thang o cao hn in p cn omt nc. V d nu o p DC 110Vta thang DC 250V, trng hp thang o thp hnin p cn o => kim bo kch kim, trng hp thang qu cao => kim bo thiu chnh x

Dng ng h vn nng o in p mt chiu DC


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*. Trng hp sai thang o:

Nu ta sai thang o, o p mt chiu nhng ta ng h thang xoay chiu th ng h s

bo sai, thng thng gi tr bo sai cao gp 2 ln gi tr thc ca in p DC, tuynhin n

h cng khng b hng .

sai thang o khi o in p mt chiu => bo sai gi tr.

* Trng hp nhm thang o

Ch - ch : Tuyt i khng nhm ng h vo thang o dng in hoc thang o itr khi ta o in p mt chiu (DC) , nu nhm ng h s b hng ngay !!

Trng hp nhm thang o dng inkhi o in p DC => ng h s b hng !


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Trng hp nhm thang o in tr khi o inp DC => ngh s b hng cc in tr bn trong!

5. Hng dn o in tr v tr khng.

Vi thang o in tr ca ng h vn nng ta c th o c rt nhiu th.

o kim tra gi tr ca in tr

o kim tra s thng mch ca mt on dy dn

o kim tra s thng mch ca mt on mch in

o kim tra cc cun dy bin p c thng mch khng

o kim tra s phng np ca t in

o kim tra xem t c b d, b chp khng.

o kim tra tr khng ca mt mch in

o kim tra i t v bng bn dn.

* s dng c cc thang o ny ng h phi c lp 2 Pn tiu 1,5V bn trong,

x dng cc thang o 1Kohm hoc 10Kohm ta phi lp Pin 9V.


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2

6. o in tr :

o kim tra in tr bng ng h vn nng

o tri s in tr ta thc hin theo cc bc sau :

Bc 1 : thang ng h v cc thang o tr, nu in tr nh th thang x1 ohm hox10 ohm, nu in tr ln th thang x1Kohm hoc 10Kohm. => sau chp hai queo v chnh trit o kim ng h bo v tr 0 ohm.

Bc 2 : Chun b o .

Bc 3 : t que o vo hai u in tr, c tr s trn thang o , Gi tr o c= ch sthang oX thang oV d : nu thang x100 ohm v ch s bo l 27 th gi tr l = 100 x 27 = 2700 ohm= 2,7 K ohm

Bc 4 : Nu ta thang o qu cao th kim ch ln mt cht , nh vy c tr s s khngchnh xc.


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Bc 5 : Nu ta thang o qu thp , kim ln qu nhiu, v c tr s cng khng chnhxc.

Khi o in tr ta chn thang o sao cho kim bo gn v tr gia vch ch s s cho chnh xc cao nht.

7. Dng thang in tr o kim tra t in

Ta c th dng thang in tr kim tra phng np v h hng ca tin , khi o tin , nu l t gm ta dng thang o x1K ohm hoc 10K ohm, nu l t ho ta dng thang x ohm hoc x 10 ohm.

Dng thang x 1K ohm kim tra t gm

Php o t gm trn cho ta bit :

T C1 cn tt => kim phng np khi ta o T C2 b d => ln kim nhng khng tr v v tr c T C3 b chp => kim ng h ln = 0 ohm v khng tr v.


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Dng thang x 10 ohm kim tra t ho

trn l php o kim tra cc t ho, t ho rt t khi b d hoc chp m ch yu l b kh gim in dung) khi o t ho bit chnh xc mc hng ca t ta cn o so snh vi mt mi c cng in dung.

trn l php o so snh hai t ho cng in dung, trong t C1 l t mi cn C2 lt c, ta thy t C2 c phng np yu hn t C1 => chng t t C2 b kh ( gimin dung )

Ch khi o t phng np, ta phi o chiu que o vi ln xem phng np.

8. Hng dn o dng in bng ng h vn nng.

Cch 1 : Dng thang o dng

o dng in bng ng h vn nng, ta o ng h ni tip vi ti tiu th v ch lch o c dng in nh hn gi tr ca thang o cho php, ta thc hin theo cc bc sau

Bc 1 : t ng h vo thang o dng cao nht . Bc 2: t que ng h ni tip vi ti, que v chiu dng, que en v chiu m Nu kim ln thp qu th gim thang o Nu kim ln kch kim th tng thang o, nu thang o thang cao nht th ng h

khng o c dng in ny. Ch s kim bo s cho ta bit gi tr dng in .

Cch 2 : Dng thang o p DC

Ta c th o dng in qua ti bng cch o st p trn in tr hn dng mc ni vi ti,in p o c chia cho gi tr tr hn dng s cho bit gi tr dng in, phng php ny cth o c cc dng in ln hn kh nng cho php ca ng h v ng h cmg an tonhn.


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Cch c tr sdng in v in p khi o nh th no ?

* c gi tr in p AC v DCKhi o in p DC th ta c gi tr trn vch ch s DCV.A

Nuta thang o 250V th ta c trn vch c gi tr cao nht l 250, tng t thang 10V th c trn vch c gi tr cao nht l 10. trng hp thang 1000V nhnkhng c vch no ghi cho gi tr 1000 th c trn vch gi tr Max = 10, gi tr oc nhn vi 100 ln

Khi o in p AC th c gi tr cng tng t. c trn vch AC.10V, nu o thanc gi tr khc th ta tnh theo t l. V d nu thang 250V th mi ch s ca vch 1s tng ng vi 25V.

Khi o dng in th c gi tr tng t c gi tr khi o in p

9. Gii thiu v ng h s DIGITAL

ng h s Digital c mt s u im so vi ng h c kh, l chnh xc cao hn,

tr khng ca ng h cao hn do khng gy st p khi o vo dng in yu, o c tns in xoay chiu, tuy nhin ng h ny c mt s nhc im l chy bng mch in tln hay hng, kh nhn kt qu trong trng hp cn o nhanh, khng o c phng npca t.


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ng h vn nng s Digital

Hng dn s dng :

* o in p mt chiu ( hoc xoay chiu )


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t ng h vo thang o in p DC hoc AC

- que ng h vo l cm " V mA" que en vo l cm "COM"

- Bm nt DC/AC chn thang o l DC nu o p mt chiu hoc AC nu o p xoay

chiu.

- Xoay chuyn mch v v tr "V" hy thang o cao nht nu cha bit r in p, n

gi tr bo dng thp phn th ta gim thang o sau.

- t thang o vo in p cn o v c gi tr trn mn hnh LCD ca ng h.

- Nu t ngc que o(vi in mt chiu) ng h s bo gi tr m (-)

* o dng in DC(AC)

Chuyn que ng h v thang mA nu o dng nh, hoc 20A nu o dng ln. Xoay chuyn mch v v tr "A"

Bm nt DC/AC chn o dng mt chiu DC hay xoay chiu AC

t que o ni tip vi mch cn o

c gi tr hin th trn mn hnh.

* o in tr

Tr li v tr dy cm nh khi o in p . Xoay chuyn mch v v tr o " ", nu cha bit gi tr in tr th chn thang o

cao nht , nu kt qu l s thp phn th ta gim xung.

t que o vo hai u in tr.

c gi tr trn mn hnh.

Chc nng o in tr cn c th o s thng mch, gi s o mt on dy dn bng

thang o tr, nu thng mch th ng h pht ra tin ku


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* o tn s

Xoay chuyn mch v v tr "FREQ" hoc " Hz"

thang o nh khi o in p .

t que o vo cc im cn o

c tr s trn mn hnh.

* o Logic

o Logic l o vo cc mch s ( Digital) hoc o cc chn ln ca vi x l, o Logic

thc cht l o trng thi c in - K hiu "1" hay khng c in "0", cch o nh sau

Xoay chuyn mch v v tr "LOGIC"

t que vo v tr cn o que en vo mass

Mn hnh ch "" l bo mc logic mc cao, ch "" l bo logic mc thp

* o cc chc nng khc

ng h vn nng s Digital cn mt s chc nng o khc nh o i t, o t in,

o Transistor nhng nu ta o cc linh kin trn, ta ln dng ng h c kh s cho k

qu tt hn v o nhanh hn.


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BI 5.

IN TR - T IN

1. Khi nim v in tr.

in tr l g ? Ta hiu mt cch n gin - in trl s cn tr dng in ca mt vtdn in, nu mt vt dn in tt th in tr nh, vt dn in km th in tr ln, vt cchin th in tr l v cng ln.

in tr ca dy dn :in tr ca dy dn ph thc vo cht liu, di v tit din ca dy. c tnh theo cng

thc sau:

R = .L / S

Trong l in tr xut ph thuc vo cht liu L l chiu di dy dn S l tit din dy dn R l in tr n v l Ohm

2. in tr trong thit b in t.

a) Hnh dng v k hiu : Trong thit b in t in tr l mt linh kin quan trng,chng c lm t hp cht cacbon v kim loi tu theo t l pha trn m ngi ta to ra cc loi in tr c tr s khc nhau.

Hnh dng ca in tr trong thit b in t.

K hiu ca in tr trn cc s nguyn l.

b) n v ca in tr

n v in tr l (Ohm) , K , M 1K = 1000


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1M = 1000 K = 1000.000

C) Cch ghi tr s ca in tr

Cc in tr c kch thc nh c ghi tr s bng cc vch mu theo mt quy cchung ca th gii.( xem hnh trn )

Cc in tr c kch thc ln hn t 2W tr ln thng c ghi tr s trc tip trn

thn. V d nh cc in tr cng xut, in tr s.

Tr s cng xut ln , tr s c ghi trc tip.

3. Cch c tr s in tr .

Quy c mu Quc t

Mu sc Gi trMu sc

Gi tr

en 0 Xanh l 5Nu 1 Xanh l 6 2 Tm 7Cam 3 Xm 8Vng 4 Trng 9

Nh vng -1

Nh bc -2

in tr thngc k hiu bng 4 vng mu , in tr chnh xcth k hiu bng 5vng mu.


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* Cch c tr s in tr 4 vng mu :

Cch c in tr 4 vng mu

- Vng s 4 l vng cui lun lun c mu nh vng hay nh bc, y l vng ch sai

s ca in tr, khi c tr s ta b qua vng ny.

- i din vi vng cui l vng s 1, tip theo n vng s 2, s 3

- Vng s 1 v vng s 2 l hng chc v hng n v- Vng s 3 l bi s ca c s 10.

- Tr s = (vng 1)(vng 2) x 10( m vng 3)

- C th tnh vng s 3 l s con s khng "0" thm vo

- Mu nh ch c vng sai s hoc vng s 3, nu vng s 3 l nh th s m ca c s

10 l s m.


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* Cch c tr s in tr 5 vng mu : ( in tr chnh xc )

- Vng s 5 l vng cui cng , l vng ghi sai s, tr 5 vng mu th mu sai s c nhi

mu, do gy kh khn cho ta khi xc inh u l vng cui cng, tuy nhin vng

cui lun c khong cch xa hn mt cht.

- i din vng cui l vng s 1

- Tng t cch c tr s ca tr 4 vng mu nhng y vng s 4 l bi s ca c s

10, vng s 1, s 2, s 3 ln lt l hng trm, hng chc v hng n v.- Tr s = (vng 1)(vng 2)(vng 3) x 10( m vng 4)

- C th tnh vng s 4 l s con s khng "0" thm vo

1. Thc hnh c tr s in tr.

Cc in tr khc nhau vng mu th 3


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- Khi cc in tr khc nhau vng mu th 3, th ta thy vng mu bi s ny thng

thay i t mu nh bc cho n mu xanh l , tng ng vi in tr < 1 n

hng M.

Cc in tr c vng mu s 1 v s 2 thay i .

hnh trn l cc gi tr in tr ta thng gp trong thc t, khi vng mu s 3 thay

i th cc gi tr in tr trn tng gim 10 ln.

2. Cc tr s in tr thng dng.

Ta khng th kim c mt in tr c tr s bt k, cc nh sn xut ch a ra khong

150 loi tr s in tr thng dng , bng di y l mu sc v tr s ca cc in tr thng

dng.

Cc gi tr in tr thng dng.


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1. Phn loi in tr.

- in tr thng : in tr thng l cc in tr c cng xut nh t 0,125W n0,5W

- in tr cng xut : L cc in tr c cng xutln hn t 1W, 2W, 5W, 10W.- in tr s, in tr nhit: L cch gi khc ca cc in tr cng xut , in tr ny c

v bc s, khi hot ng chng to nhit.

Cc in tr : 2W - 1W - 0,5W - 0,25W

in tr s hay tr nhit

2. Cng xut ca in tr.

Khi mc in tr vo mt on mch, bn thn in tr tiu th mt cng xut P tnh c

theo cng thc

P = U . I = U2/ R = I2.R

- Theo cng thc trn ta thy, cng xut tiu th ca in tr ph thuc vo dng in i qu

in tr hoc ph thuc vo in p trn hai u in tr.

- Cng xut tiu th ca in tr l hon ton tnh c trc khi lp in tr vo mch.

- Nu em mt in tr c cng xut danh nh nh hn cng xut n s tiu th th in tr

s b chy.

- Thng thng ngi ta lp in tr vo mch c cng xut danh nh > = 2 ln cng xu

m n s tiu th.

in tr chy do qu cng xut


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- s trn cho ta thy : Ngun Vcc l 12V, cc in tr u c tr s l 120 nhng c

cng xut khc nhau, khi cc cng tc K1 v K2 ng, cc in tr u tiu th mt cng

xut l

P = U2/ R = (12 x 12) / 120 = 1,2W

- Khi K1 ng, do in tr c cng xut ln hn cng xut tiu th , nn in tr khngchy.

- Khi K2 ng, in tr c cng xut nh hn cng xut tiu th , nn in tr b chy .

3. Bin tr, trit p :

Bin tr L in tr c th chnh thay i gi tr, c k hiu l VR chng c hnh dn

nh sau :

Hnh dng bin tr K hiu trn s

Bin tr thng rp trong my phc v cho qu trnh sa cha, cn chnh ca k thut vinbin tr c cu to nh hnh bn di.

Cu to ca bin tr

- Trit p : Trit pcng tng t bin tr nhng c thm cn chnh v thng b tr pha

trc mt my cho ngi s dng iu chnh. V d nh - Trit p Volume, trit p Bass,

Treec v.v.. , trit p ngha l trit ra mt phn in p t u vo tu theo mc chnh.


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K hiu trit p trn s nguyn l.

Hnh dng trit p Cu to trong trit p

Trong thc t , khi ta cn mt in tr c tr s bt k ta khng th c c , v in tr chc sn xut khong trn 100 loi c cc gi tr thng dng, do c mt in tr bt kta phi u in tr song song hoc ni tip.

1. in tr mc ni tip .

in tr mc ni tip.

- Cc in tr mc ni tip c gi tr tng ng bng tng cc in tr thnh phn cngli. Rtd = R1 + R2 + R3


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- Dng in chy qua cc in tr mc ni tip c gi tr bng nhau v bng I

I = ( U1 / R1) = ( U2 / R2) = ( U3 / R3 )

- T cng thc trn ta thy rng , st p trn cc in tr mc ni tip t l thun vi gi trint tr .

2. in tr mc song song.

in tr mc song song

Cc in tr mc song song c gi tr tng ng Rtd c tnh bi cng thc (1Rtd) = (1 / R1) + (1 / R2) + (1 / R3)

Nu mch ch c 2 in tr song song thRtd = R1.R2 / ( R1 + R2)

Dng in chy qua cc in tr mc song song t l nghch vi gi tr in tr .I1 = ( U / R1) , I2 = ( U / R2) , I3 =( U / R3 ) in p trn cc in tr mc song song lun bng nhau

3. in tr mc hnhp

in tr mc hn hp.

- Mc hn hp cc in tr to ra in tr ti u hn .


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- V d: nu ta cn mt in tr 9K ta c th mc 2 in tr 15K song song sau mc nitip vi in tr 1,5K .

4 . ng dng ca in tr :in tr c mt mi ni trong thit b in t v nh vy in tr l linh kin quan trng

khng th thiu c , trong mch in , in tr c nhng tc dng sau :

Khng ch dng in qua ti cho ph hp,V d c mt bng n 9V, nhng ta ch cngun 12V, ta c th u ni tip bng n vi in tr st p bt 3V trn in tr.

-- u ni tip vi bng n mt in tr.

- Nh hnh trn ta c th tnh c tr s v cng xut ca in tr cho ph hp nh sau:Bng n c in p 9V v cng xut 2W vy dng tiu th l I = P / U = (2 / 9 ) = Ampe cng chnh l dng in i qua in tr.

- V ngun l 12V, bng n 9V nn cn st p trn R l 3V vy ta suy ra in tr ctm l R = U/ I = 3 / (2/9) = 27 / 2 = 13,5

- Cng xut tiu th trn in tr l : P = U.I = 3.(2/9) = 6/9 W v vy ta phi dngin tr c cng xut P > 6/9 W

Mc in tr thnh cu phn p c c mt in p theo mun t mt in p chtrc.

Cu phn p ly ra p U1 tu .

T ngun 12V trn thng qua cu phn p R1 v R2 ta ly ra in p U1, p U1 ph thuvo gi tr hai in tr R1 v R2.theo cng thc .

U1 / U = R1 / (R1 + R2) => U1 = U.R1(R1 + R2)


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Thay i gi tr R1 hoc R2 ta s thu c in p U1 theo mun.

Phn cc cho bng bn dn hot ng .

Mch phn cc cho Transistor

Tham gia vo cc mch to dao ngR C

Mch to dao ng s dng IC 555

T in : T in l linh kin in t th ng c s dng rt rng ri trong cc mch it, chng c s dng trong cc mch lc ngun, lc nhiu, mch truyn tn hiu xoay chiumch to dao ng .vv...

1. Cu to ca t in .

Cu to ca t in gm hai bn cc t song song, gia c mt lp cch in gi l inmi.

Ngi ta thng dng giy, gm , mica, giy tm ho cht lm cht in mi v t in cnc phn loi theo tn gi ca cc cht in mi ny nh T giy, T gm, T ho.


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Cu to t gm Cu to t ho

2.Hnh dng thc t ca t in.

Hnh dng ca t gm.

Hnh dng ca t ho


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3. in dung , n v v k hiu ca t in.* in dung : L i lng ni ln kh nng tch in trn hai bn cc ca t in, in

dung ca t in ph thuc vo din tch bn cc, vt liu lm cht in mi v khong cchgi hai bn cc theo cng thc

C = . S / d

Trong C : l in dung t in , n v l Fara (F) : L hng s in mi ca lp cch in. d : l chiu dy ca lp cch in. S : l din tch bn cc ca t in.

* n v in dung ca t : n v l Fara (F) , 1Fara l rt ln do trong thc tthng dng cc n v nh hn nh MicroFara (F) , NanoFara (nF), PicoFara (pF).

1 Fara = 1000 Fara = 1000.000 n F = 1000.000.000 p F 1 Fara = 1000 n Fara 1 n Fara = 1000 p Fara

* K hiu :T in c k hiu l C (Capacitor)

K hiu ca t in trn s nguyn l.

phng np ca t in .

Mt tnh cht quan trng ca t in l tnh cht phng np ca t , nh tnh cht ny m t ckh nng dn in xoay chiu.


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Minh ho v tnh cht phng np ca t in.

* T np in :Nh hnh nh trn ta thy rng , khi cng tc K1 ng, dng in tngun U i qua bng n np vo t, dng np ny lm bng n lo sng, khi t np yth dng np gim bng 0 v vy bng n tt.

* T phng in : Khi t np y, nu cng tc K1 m, cng tc K2 ng th dng int cc dng (+) ca t phng qua bng n v cc m (-) lm bng n lo sng, khi t

phng ht in th bng n tt.

=> Nu in dung t cng ln th bng n lo sng cng lu hay thi gian phng np cnglu.

2 . Cch c gi tr in dung trn t in.

* Vi t ho : Gi tr in dung ca t ho c ghi trc tip trn thn t

=> T ho l t c phn cc (-) , (+) v lun lun c hnh tr .

T ho ghi in dung l 185 F / 320 V

* Vi t giy , t gm : T giy v t gm c tr s ghi bng k hiu


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T gm ghi tr s bng k hiu.

Cch c : Ly hai ch s u nhn vi 10(M s th 3 ) V d t gm bn phi hnh nh trn ghi 474K ngha l

Gi tr = 47 x 104= 470000p ( Ly n v l pic Fara)= 470 n Fara = 0,47 F

Ch K hocJ cui l ch sai s 5% hay 10% ca t in .

* Thc hnh c tr s ca t in.

Cch c tr s t git v t gm .Ch : ch K l sai s ca t .50V l in p cc i m t chu c.

* T giy v t gm cn c mt cch ghi tr s khc l ghi theo s thp phn v ly n v lMicroFara

Mt cch ghi tr s khc ca t giy v t gm.

3. ngh ca gi tr in p ghi trn thn t :

Ta thy rng bt k t in no cng c ghi tr s in p ngay sau gi tr in duny chnh l gi tr in p cc i m t chu c, qu in p ny t s b n.


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Khi lp t vo trong mt mch in c in p l U th bao gi ngi ta cng lp tin c gi tr in p Max cao gp khong 1,4 ln.

V d mch 12V phi lp t 16V, mch 24V phi lp t 35V. vv...

T in c nhiu loinh T giy, T gm, T mi ca , T ho nhng v tnh cht th ta phn l hai loi chnh l t khng phn cc v t phn cc

1. T giy, T gm, T mica. (T khng phn cc )Cc loi t ny khng phn bit m dng v thng c in dung nh t 0,47 F tr

xung, cc t ny thng c s dng trong cc mch in c tn s cao hoc mch lcnhiu.

T gm - l t khng phn cc.

2. T ho ( T c phn cc )T ho l t c phn cc m dng , t ho c tr s ln hn v gi tr t 0,47F n

khong 4.700 F , t ho thng c s dng trong cc mch c tn s thp hoc dng lngun, t ho lun lun c hnh tr..

T ho - L t c phn cc m dng.


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3. T xoay .T xoay l t c th xoay thay i gi tr in dung, t ny thng c lp trong Radi

thay i tn s cng hng khi ta d i.

T xoay s dng trong Radio

1. o kim tra t giy v t gm.

T giy v t gm thng hng dng b d r hoc b chp, pht hin t d r hoc bchp ta quan st hnh nh sau y .

o kim tra t giy hoc t gm .

hnh nh trn l php o kim tra t gm, c ba t C1 , C2 v C3 c in dung bngnhau, trong C1 l t tt, C2 l t b d v C3 l t b chp.


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Khi o t C1 ( T tt ) kim phng ln 1 cht ri tr v v tr c. ( Lu cc t nh qu< 1nF th kim s khng phng np )

Khi o t C2 ( T b d ) ta thy kim ln lng chng thang o v dng li khng tr vv tr c.

Khi o t C3 ( T b chp ) ta thy kim ln = 0 v khng tr v. Lu : Khi o kim tra t giy hoc t gm ta phi ng h thang x1K hoc

x10K, v phi o chiu kim ng h vi ln khi o.

2. o kim tra t ho

T ho t khi b d hay b chp nh t giy, nhng chng li hay hng dng b kh ( khho cht bn trong lp in mi ) lm in dung ca t b gim , kim tra t ho , ta thnso snh phng np ca t vi mt t cn tt c cng in dung, hnh nh di y minhho cc bc kim tra t ho.

o kim tra t ho

kim tra t ho C2 c tr s 100F c b gim in dung hay khng, ta dng t C1cn mi c cng in dung v o so snh.

ng h thang t x1 n x100 ( in dung cng ln th thang cng thp ) o vo hai t v so snh phng np , khi o ta o chiu que o vi ln. Nu hai t phng np bng nhau l t cn kim tra cn tt, trn ta thy t C2 phngnp km hn do t C2 trn b kh. Trng hp kim ln m khng tr v l t b d.

Ch : Nu kim tra t in trc tip trn mch , ta cn phi ht rng mt chn t khimch in, sau kim tra nh trn.


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1 . T in mc ni tip .

Cc t in mc ni tip c in dung tng ng C t c tnh bi cng thc : 1C t = (1 / C1 ) + ( 1 / C2 ) + ( 1 / C3 )

Trng hp ch c 2 t mc ni tip th C t = C1.C2 / ( C1 + C2 ) Khi mc ni tip th in p chu ng ca t tng ng bng tng in p ca cc

t cng li. U t = U1 + U2 + U3

Khi mc ni tip cc t in, nu l cc t ho ta cn ch chiu ca t in, cc m trc phi ni vi cc dng t sau:

T in mc ni tip T in mc song song

2 . T in mc song song.

Cc t in mc song song th c in dung tng ng bng tng in dung ca ct cng li . C = C1 + C2 + C3

in p chu ng ca t in tng tng bng in p ca t c in p thp nht. Nu l t ho th cc t phi c u cng chiu m dng.

3. ng dng ca t in .

T in c s dng rt nhiu trong k thut in v in t, trong cc thit b in t, tin l mt linh kin khng th thiu c, mimch in t u c mt cng dng nht nhnh truyn dn tn hiu , lc nhiu, lc in ngun, to dao ng ..vv...

Di y l mt s nhng hnh nh minh ho v ng dng ca t in.


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* T in trong mch lc ngun.

T ho trong mch lc ngun.

Trong mch lc ngun nh hnh trn , t ho c tc dng lc cho in p mt chiu saukhi chnh lu c bng phng cung cp cho ti tiu th, ta thy nu khng c tth p DC sau i t l in p nhp nh, khi c t in p ny c lc tng i phn

t in cng ln th in p DC ny cng phng.

* T in trong mch dao ng a hi to xung vung.

Mch dao ng a hi s dng 2 Transistor

Bn c th lp mch trn vi cc thng s cho trn s . Hai n bo sng s dng n Led du song song vi cc CE ca hai Transistor, ch

u ng chiu m dng.

CUN DY - BIN P

1. Cu to ca cun cm.Cun cm gm mt s vng dy qun li thnh nhiu vng, dy qun c sn emay cch

in, li cun dy c th l khng kh, hoc l vt liu dn t nh Ferrite hay li thp k thu.


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Cun dy li khng kh Cun dy li Ferit

K hiu cun dy trn s : L1 l cun dy likhng kh, L2 l cun dy li ferit, L3 l cun

dy c li chnh, L4 l cun dy li thp k thut

2. Cc i lng c trng ca cun cm.

a) H s t cm ( nh lut Faraday)H s t cm l i lng c trng cho sc in ng cm ng ca cun dy khi c dng

in bin thin chy qua.

L = ( r.4.3,14.n2.S.10-7) / l

o L : l h s t cm ca cun dy, n v l Henrry (H)o

n : l s vng dy ca cun dy.o

l : l chiu di ca cun dy tnh bng mt (m)o S : l tit din ca li, tnh bng m2o r : l h s t thm ca vt liu lm li .

b) Cm khngCm khng ca cun dy l i lng c trng cho s cn tr dng in ca cun dy i

vi dng in xoay chiu .

ZL = 2.3,14.f.L

o Trong : ZL l cm khng, n v l o

f : l tn s n v l Hzo L : l h s t cm , n v l Henry


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Th nghim v cm khng ca cundy vi dng in xoay chiu

* Th nghim trn minh ho: Cun dy ni tip vi bng n sau c u vo cc

ngun in 12V nhng c tn s khc nhau thng qua cc cng tc K1, K2 , K3 , khi K1 n

dng in mt chiu i qua cun dy mnh nht ( V ZL = 0 ) => do bng n sng nht,

khi K2 ng dng in xoay chu 50Hz i qua cun dy yy hn ( doZL tng ) => bng n

sng yu i, khi K3 ng , dng in xoay chiu 200Hz i qua cun dy yu nht ( do ZL tncao nht) => bng n sng yu nht.

=>Kt lun: Cm khng ca cun dy t l vi h s t cm ca cun dy v t l vi tn

s dng in xoay chiu, ngha l dng in xoay chiu c tn s cng cao th i qua cun d

cng kh, dng in mt chiu c tn s f = 0 Hz v vy vi dng mt chiu cun dy c cm

khng ZL = 0

c) in tr thun ca cun dy.in tr thun ca cun dy l in tr m ta c th o c bng ng h vn nng, thng

thng cun dy c phm cht tt th in tr thun phi tng i nh so vi cm khng,

in tr thun cn gi l in tr tn hao v chnh in tr ny sinh ra nhit khi cun dy ho

ng.

3. Tnh cht np , x ca cun cm

* Cun dy np nng lng : Khi cho mt dng in chy qua cun dy, cun dy np mt

nng lng di dng t trng c tnh theo cng thc

W = L.I2/ 2

W : nng lng ( June ) L : H s t cm ( H ) I dng in.


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Th nghim v tnh np x ca cun dy.

th nghim trn : Khi K1 ng, dng in qua cun dy tng dn ( do cun dy sinh racm khng chng li dng in tng t ngt ) v vybng n sng t t, khi K1 va ngt vK2 ng , nng lng np trong cun dy to thnh in p cm ng phng ngc li qua

bng n lm bng n lo sng => l hin tng cun dy x in.

1. Loa ( Speaker )

Loa l mt ng dng ca cun dy v t trng.

Loa 4- 20W ( Speaker )


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Cu to v hot ng ca Loa ( Speaker )

Cu to ca loa :Loa gm mt nam chm hnh tr c hai cc lng vo nhau , cc N giv cc S xung quanh, gia hai cc to thnh mt khe t c t trng kh mnh, mt cun

dy c gn vi mng loa v c t trong khe t, mng loa c bng gn cao su mm

gip cho mng loa c th d dng dao ng ra vo.

Hot ng : Khi ta cho dng in m tn ( in xoay chiu t 20 Hz => 20.000Hz ) chy

qua cun dy, cun dy to ra t trng bin thin v b t trng c nh ca nam chm y

ra, y vo lm cun dy dao ng => mng loa dao ng theo v pht ra m thanh.

Ch : Tuyt i ta khng c a dng in mt chiu vo loa , v dng in mt chiu

ch to ra t trng c nh v cun dy ca loa ch lch v mt hng ri dng li, khi

dng mt chiu qua cun dy tng mnh ( do khng c in p cm ng theo chiu ngc lai

v vy cun dy s b chy .

2 . Micro

Micro


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Thc cht cu to Micro l mt chic loa thu nh, v cu to Micro ging loa nhng Micro

c s vng qun trn cun dy ln hn loa rt nhiu v vy tr khng ca cun dy micro l r

ln khong 600 ( tr khng loa t 4 - 16 ) ngoi ra mng micro cng c cu to rt

mng d dng dao ng khi c m thanh tc ng vo. Loa l thit b chuyn dng in

thnh m thanh cn micro th ngc li , Micro i m thanh thnh dng in m tn.

3.R le ( Relay)

R le

R le cng l mt ng dng ca cun dy trong sn xut thit b in t, nguyn l hot

ng ca Rle l bin i dng in thnh t trng thng qua qun dy, t trng li to

thnh lc c hc thng qua lc ht thc hin mt ng tc v c kh nh ng m cng t

ng m cc hnh trnh ca mt thit b t ng vv...

Cu to v nguyn l hot ng ca R le

1. Cu to ca bin p.

Bin p l thit b bin i in p xoay chiu, cu to bao gm mt cun s cp ( a

in p vo ) v mt hay nhiu cun th cp ( ly in p ra s dng) cng qun trn mt li

t c th l l thp hoc li ferit .


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K hiu ca bin p

2. T s vng / vol ca bin p .

Gi n1 v n2 l s vng ca qun s cp v th cp. U1 v I1 l in p v dng in i vo cun s cp U2 v I2 l in p v dng in i ra t cun th cp.

Ta c cc h thc nh sau :

U1 / U2 = n1 / n2 in p trn hai cun dy s cp v th cp t l thun vi svng dy qun.

U1 / U2 = I2 / I1 Dng in trn hai u cun dy t l nghch vi in p, ngha lnu ta ly ra in p cng cao th cho dng cng nh.

3. Cng xut cabin p .

Cng xut ca bin p ph thuc tit din ca li t, v ph thuc vo tn s ca dng inxoay chiu, bin p hot ng tn s cng cao th cho cng xut cng ln.

4. Phn loi bin p .

* Bin p ngun v bin p m tn:

Bin p ngun Bin p ngun hnh xuyn

Bin p ngun thng gp trong Cassete, mply .. , bin p ny hot ng tn s in

li 50Hz , li bin p s dng cc l Tnsilic hnh ch E v I ghp li, bin p ny c t s

vng / vol ln.


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Bin p m tn s dng lm bin p o pha v bin p ra loa trong cc mch khuych i

cng xut m tn,bin p cng s dng l Tnsilic lm li t nh bin p ngun, nhng l

tnsilic trong bin p m tn mng hn trnh tn hao, bin p m tn hot ng tn s ca

hn , v vy c s vng vol thp hn, khi thit k bin p m tn ngi ta thng ly gi tr t

s trung bnh khong 1KHz - n 3KHz.

* Bin p xung & Cao p .

Bin p xung Cao p

Bin p xung l bin p hot ng tn s cao khong vi chc KHz nh bin p trong cc

b ngun xung , bin p cao p . li bin p xung lm bng ferit , do hot ng tn s cao

nn bin p xung cho cng xut rt mnh, so vi bin p ngun thng thng c cng trng

lng th bin p xung c th cho cng xut mnh gp hng chc ln.


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BI 7.

DIODE TRANSISTOR

1. Cht bn dn.

Cht bn dn l nguyn liu sn xut ra cc loi linh kin bn dn nh Diode, Transistor

IC m ta thy trong cc thit b in t ngy nay.

Cht bn dn l nhng cht c c im trung gian gia cht dn in v cht cch in, v

phng din ho hc th bn dn l nhng cht c 4 in t lp ngoi cng ca nguyn t.

l cc cht Germanium ( Ge) v Silicium (Si)

T cc cht bn dn ban u ( tinh khit) ngi ta phi to ra hai loibn dn l bn dn lo

N v bn dn loi P, sau ghp cc ming bn dn loi N v P li ta thu c Diode hay

Transistor.

Si v Ge u c ho tr 4, tc l lp ngoi cng c 4 in t, th tinh khit cc nguyn t

(Ge) lin kt vi nhau theo lin kt cng ho tr nh hnh di.

Cht bn dn tinh khit .

2. Cht bn dn loi N

* Khi ta pha mt lng nh cht c ho tr 5 nh Phospho (P) vo cht bn dn Si th mt

nguyn t P lin kt vi 4 nguyn t Si theo lin kt cng ho tr, nguyn t Phospho ch c 4in t tham gia lin kt v cn d mt in t v tr thnh in t t do => Cht bn dn lc

ny tr thnh tha in t ( mang in m) v c gi l bn dn N ( Negative : m ).


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Cht bn dn N

3. Cht bn dn loi P

Ngc li khi ta pha thm mt lng nh cht c ho tr 3 nh Indium (In) vo cht bn d

Si th 1 nguyn t Indium s lin kt vi 4 nguyn t Si theo lin kt cng ho tr v lin kt

b thiu mt in t => tr thnh l trng ( mang in dng) v c gi l cht bn dn P

Cht bn dn P

1. Tip gip P - N v Cu to ca Diode bn dn.

Khi c c hai cht bn dn l P v N , nu ghp hai cht bn dn theo mt tip gip

-N ta c mt Diode, tip gip P-N c c im : Ti b mt tip xc, cc in t d tha

trong bn dn N khuych tn sang vng bn dn P lp vo cc l trng => to thnh mt

lp Ion trung ho v in => lp Ion ny to thnh min cch in gia hai cht bn dn.

Mi tip xc P - N => Cu to ca Diode .


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* hnh trn l mi tip xc P - N v cng chnh l cu to ca Diode bn dn.

K hiu v hnh dng ca Diode bn dn.

2. Phn cc thun cho Diode.

Khi ta cp in p dng (+) vo Ant ( vng bn dn P ) v in p m (-) vo Katt (

vng bn dn N ) , khi di tc dng tng tc ca in p, min cch in thu hp li, kh

in p chnh lch gi hai cc t 0,6V ( vi Diode loi Si ) hoc 0,2V ( vi Diode loi Ge )

th din tch min cch in gim bng khng => Diode bt u dn in. Nu tip tc tngin p ngun th dng qua Diode tng nhanh nhng chnh lch in p gia hai cc ca

Diode khng tng (vn gi mc 0,6V )

Diode (Si) phn cc thun - Khi Dode dnin p thun c gim mc 0,6V

ng c tuyn ca in p thun qua Diode

* Kt lun : Khi Diode (loi Si) c phn cc thun, nu in p phn cc thun < 0,6V t

cha c dng i qua Diode, Nu p phn cc thun t = 0,6V th c dng i qua Diode sau

dng in qua Diode tng nhanh nhng st p thun vn gi gi tr 0,6V .

3. Phn cc ngc cho Diode.

Khi phn cc ngc cho Diode tc l cp ngun (+) vo Katt (bn dn N), ngun (-) vo


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Ant (bn dn P), di s tng tc ca in p ngc, min cch in cng rng ra v ngn

cn dng in i qua mi tip gip, Diode c thchiu c in p ngc rt ln khong

1000V th diode mi b nh thng.

Diode ch b chy khi p phn cc ngc tng > = 1000V

4. Phng php o kim tra Diode

o kim tra Diode

t ng h thang x 1 , t hai que o vo hai u Diode, nu :

o chiu thun que en vo Ant, que vo Katt => kim ln, o chiu o kim

khng ln l => Diode tt

Nu o c hai chiu kim ln = 0 => l Diode b chp. Nu o thun chiu m kim khng ln => l Diode b t.

php o trn th Diode D1 tt , Diode D2 b chp v D3 b t

Nu thang 1K m o ngc vo Diode kim vn ln mt cht l Diode b d.

5. ng dng ca Diode bn dn .


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* Do tnh cht dn in mt chiu nn Diode thng c s dng trong cc mch chnh l

ngun xoay chiu thnh mt chiu, cc mch tch sng, mchgim p phn cc cho transistor

hot ng . trong mch chnh lu Diode c th c tch hp thnh Diode cu c dng .

Diode cu trong mch chnh lu in xoay chiu .

1. Diode Zener

* Cu to :Diode Zener c cu to tng t Diode thng nhng c hai lp bn dn P - N

ghp vi nhau, Diode Zener c ng dng trong ch phn cc ngc, khi phn cc thun

Diode zener nh diode thng nhng khi phn cc ngc Diode zener s gim li mt mc

in p c nh bng gi tr ghi trn diode.

Hnh dng Diode Zener ( Dz )

K hiu v ng dng ca Diode zener trong mch.

- S trn minh ho ng dng ca Dz, ngun U1 l ngun c in p thay i, Dz l diod

n p, R1 l tr hn dng.

- Ta thy rng khi ngun U1 > Dz th p trn Dz lun lun c nh cho d ngun U1 thay

i.


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- Khi ngun U1 thay i th dng ngc qua Dz thay i, dng ngc qua Dz c gi tr gi

hn khong 30mA.

- Thng thng ngi ta s dng ngun U1 > 1,5 => 2 ln Dz v lp tr hn dng R1 sao

cho dng ngc ln nht qua Dz< 30mA.

Nu U1 < Dz th khi U1 thay i p trn Dz cng thay iNu U1 > Dz th khi U1 thay i => p trn Dz khng i.

2. Diode Thu quang. ( Photo Diode )

Diode thu quang hot ng ch phn cc nghch, v diode c mt ming thu tinh nh sng chiu vo mi P - N , dng in ngc qua diode t l thun vi cng nh sng

chiu vo diode.

K hiu ca Photo Diode

Minh ho s hot ng ca Photo Diode

3. Diode Pht quang ( Light Emiting Diode : LED )

Diode pht phang l Diode pht ra nh sng khi c phn cc thun, in p lm vic c

LED khong 1,7 => 2,2V dng qua Led khong t 5mA n 20mA


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Led c s dng lm n bo ngun, n nhy trang tr, bo trng thi c in . vv...

Diode pht quang LED

4. Diode Varicap ( Diode bin dung )

Diode bin dung l Diode c in dung nh t in, v in dung bin i khi ta thay i

in p ngc t vo Diode.

n dng ca Diode bin dung Varicap ( VD )

trong mch cng hng

- hnh trn khi ta chnh trit p VR, in p ngc t vo Diode Varicap thay i , in

dung ca diode thay i => lm thay i tn s cng hng ca mch.

- Diode bin dung c s dng trong cc b knh Ti vi mu, trong cc mch iu chnh ts cng hng bng in p.

5. Diode xung

Trong cc b ngun xung th u ra ca bin p xung , ta phi dng Diode xung chn

lu. diode xung l diode lm vic tn s cao khong vi chc KHz , diode nn in thng

thng khng th thay th vo v tr diode xung c, nhng ngc li diode xung c th tha

th cho v tr diode thng, diode xung c gi thnh cao hn diode thng nhiu ln.

V c im , hnh dng th Diode xung khng c g khc bit vi Diode thng, tuy nhinDiode xung thng c vng dnh du t nt hoc nh du bng hai vng

K hiu ca Diode xung


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6. Diode tch sng.

L loi Diode nh v bng thu tinh v cn gi l diode tip im v mt tip xc gia hai

cht bn dn P - N ti mt im trnh in dung k sinh, diode tch sng thng dng tron

cc mch cao tn dng tch sng tn hiu.

7. Diode nn in.

L Diode tip mt dng nn in trong cc b chnh lu ngun AC 50Hz , Diode nythng c 3 loi l 1A, 2A v 5A.

Diode nn in 5A

1. Cu to ca Transistor. ( Bng bn dn )

Transistor gm ba lp bn dn ghp vi nhau hnh thnh hai mi tip gip P-N , nu ghp

theo th t PNP ta c Transistor thun , nu ghp theo th t NPN ta c Transistor

ngc. v phng din cu to Transistor tng ng vi hai Diode u ngc chiu nhau

Cu to Transistor

- Ba lp bn dn c ni ra thnh ba cc , lp gia gi l cc gc k hiu l B ( Base ), l

bn dn B rt mng v c nng tp cht thp.

- Hai lp bn dn bn ngoi c ni ra thnh cc pht ( Emitter ) vit tt l E, v cc thu

hay cc gp ( Collector ) vit tt l C, vng bn dn E v C c cng loi bn dn (loi N


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hay P ) nhng c kch thc v nng tp cht khc nhau nn khng hon v cho nhau

c.

2. Nguyn tc hot ng ca Transistor.

* Xt hot ng ca Transistor NPN .

Mch kho st v nguyn tc hotng ca transistor NPN

- Ta cp mt ngun mt chiu UCE vo hai cc C v E trong (+) ngun vo cc C v (-)

ngun vo cc E.

-

Cp ngun mt chiu UBE i qua cng tc v tr hn dng vo hai cc B v E , trong cc (+) vo chn B, cc (-) vo chn E.

- Khi cng tc m , ta thy rng, mc d hai cc C v E c cp in nhng vn khng

c dng in chy qua mi CE ( lc ny dng IC = 0 )

- Khi cng tc ng, mi P-N c phn cc thun do c mt dng in chy t (+)

ngun UBE qua cng tc => qua R hn dng => qua mi BE v cc (-) to thnh dng IB

- Ngay khi dng IB xut hin => lp tc cng c dng IC chy qua mi CE lm bng n

pht sng, v dng IC mnh gp nhiu ln dng IB

- Nh vy r rng dng IC hon ton ph thuc vo dng IB v ph thuc theo mt cngthc .

IC = .IB

- Trong IC l dng chy qua mi CE- IB l dng chy qua mi BE- l h s khuych i ca Transistor


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Gii thch: Khi c in p UCE nhng cc in t v l trng khng th vt qua mi tip

gip P-N to thnh dng in, khi xut hin dng IBE do lp bn dn P ti cc B rt mng

v nng pha tp thp, v vys in t t do t lp bn dn N ( cc E ) vt qua tip gip

sang lp bn dn P( cc B ) ln hn s lng l trng rt nhiu, mt phn nh trong s cc

in t th vo l trng to thnh dng IB cn phn ln s in t b ht v pha cc C d

tc dng ca in p UCE => to thnh dng ICE chy qua Transistor.

* Xt hot ng ca Transistor PNP .

S hot ng ca Transistor PNP hon ton tng t Transistor NPN nhng cc tnh ca

cc ngun in UCE v UBE ngc li . Dng IC i t E sang C cn dng IB i t E sang B.

1. K hiu & hnh dng Transistor .

K hiu ca Transistor

Transistor cng xut nh Transistor cng xut ln

2. K hiu ( trn thn Transistor )

* Hin nay trn th trng c nhiu loi Transistor ca nhiu nc sn xut nhng thng

dng nht l cc transistor ca Nht bn, M v Trung quc.

Transistor Nht bn: thng k hiu l A..., B..., C..., D... V d A564, B733, C82

D1555trong cc Transistor k hiu l A v B l Transistor thun PNP cn k hiu

C v D l Transistor ngc NPN. cc Transistor A v C thng c cng xut nh v

tn s lm vic cao cn cc Transistor B v D thng c cng xut ln v tn s lm

vic thp hn.


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Transistor do M sn xut. thng k hiu l 2N... v d 2N3055, 2N4073 vv...

Transistor do Trung quc sn xut: Bt u bng s 3, tip theo l hai ch ci. Ch

ci thc nht cho bit loi bng : Ch A v B l bng thun , ch C v D l bng

ngc, ch th hai cho bit c im : X v P l bng m tn, A v G l bng cao tn.

Cc ch s sau ch th t sn phm. Th d : 3CP25 , 3AP20 vv..

3. Cch xc nh chn E, B, C ca Transistor.

- Vi cc loi Transistor cng xut nhth th t chn C v B tu theo bng ca nc n

s xut , nhng chn E lun bn tri nu ta Transistor nh hnh di

- Nu l Transistor do Nht sn xut : th d Transistor C828, A564 th chn C gia ,

chn B bn phi.

- Nu l Transistor Trung quc sn xut th chn B gia , chn C bn phi.

- Tuy nhin mt s Transistor c sn xut nhi th khng theo th t ny => bit chn

xc ta dng phng php o bng ng h vn nng.

Transistor cng xut nh.

Vi loi Transistor cng xut ln(nh hnh di ) th hu ht u c chung th t

chn l : Bn tri l cc B, gia l cc C v bn phi l cc E.

Transistor cng xut ln thng c th t chn nh trn.


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* o xc nh chn B v C

- Vi Transistor cng xut nh th thng thng chn E bn tri nh vy ta ch xc nh

chn B v suy ra chn C l chn cn li.

- ng h thang x1 , t c nh mt que o vo tng chn , que kia chuyn sang hai

chn cn li, nu kim ln = nhau th chn c que t c nh l chn B, nu que ng h c

nh l que en th l Transistor ngc, l que th l Transistor thun..

1. Phng php kim tra Transistor .

Transistor khi hot ng c thh hng do nhiu nguyn nhn, nh hng do nhit ,

m, do in p ngun tng cao hoc do cht lng ca bn thn Transistor, kim tra

Transistor bn hy nh cu to ca chng.

Cu to ca Transistor

- Kim tra Transistor ngc NPN tng t kim tra hai Diode u chung cc Ant, im

chung l cc B, nu o t B sang C v B sang E ( que en vo B ) th tng ng nh o

hai diode thun chiu => kim ln , tt c cc trng hp o khc kim khng ln.

- Kim tra Transistor thun PNP tng t kim tra hai Diode u chung cc Katt, im

chung l cc B ca Transistor, nu o t B sang C v B sang E ( que vo B ) th tng

ng nh o hai diode thun chiu => kim ln , tt c cc trng hp o khc kim khng

ln.

- Tri vi cc iu trn l Transistor b hng.

Transistor c th b hng cc trng hp .

* o thun chiu t B sang E hoc t B sang C => kim khng ln l transistor

BE hoc t BC


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* o t B sang E hoc t B sang C kim ln c hai chiu l chp hay d BE hoc

BC.

* o gia C v E kim ln l b chp CE.

* Cc hnh nh minh ho khi o kim tra Transistor.

Php o cho bit Transistor cn tt .

Minh ho php o trn : Trc ht nhn vo k hiu ta bit c Transistor trn l

bng ngc, v cc chn ca Transistor ln lt l ECB ( da vo tn Transistor ).

Bc 1 : Chun b o ng h thang x1

Bc 2 v bc 3 : o thun chiu BE v BC => kim ln .

Bc 4 v bc 5 : o ngc chiu BE v BC => kim khng ln.

Bc 6 : o gia C v E kim khng ln

=> Bng tt.

----------------------------------------------------------------------


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Php o cho bit Transistor b chp BE

Bc 1 : Chun b .

Bc 2 : o thun gia B v E kim ln = 0

Bc 3: o ngc gia B v E kim ln = 0

=> Bng chp BE

-----------------------------------------------------------------

Php o cho bit bng b t BE


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Bc 1 : Chun b .

Bc 2 v 3 : o c hai chiu gia B v E kim khng ln.

=> Bng t BE

---------------------------------------------------------

Php o cho thy bng b chp CE

- Bc 1 : Chun b .

- Bc 2 v 4 : o c hai chiu gia C v E kim ln = 0

- => Bng chp CE

- Trng hp o gia C v E kim ln mt cht l b d CE.

1. Cc thng s k thut ca Transistor

- Dng in cc i : L dng in gii hn ca transistor, vt qua dng gii hn nyTransistor s b hng.

- in p cc i : L in p gii hn ca transistor t vo cc CE , vt qua in p

gii hn ny Transistor s b nh thng.

- Tn s ct : L tn s gii hn m Transistor lm vic bnh thng, vt qu tn s ny t

khuych i ca Transistor b gim .

- H s khuych i : L t l bin i ca dng ICE ln gp bao nhiu ln dng IBE


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- Cng xut cc i : Khi hoat ng Transistor tiu tn mt cng xut P = UCE . ICE nu

cng xut ny vt qu cng xut cc i ca Transistor th Transistor s b hng .

2. Mt s Transistor c bit .

* Transistor s ( DigitalTransistor ): Transistor s c cu to nh Transistor thng

nhng chn B c u thm mt in tr vi chc K

Transistor s thng c s dng trong cc mch cng tc , mch logic, mch iu khin

khi hot ng ngi ta c th a trc tip p lnh 5V vo chn B iu khin n ngt m

Minh ho ng dng ca Transistor Digital

* K hiu : Transistor Digital thng c cc k hiu l DTA...( dn thun ), DTC...( n

ngc ) , KRC...( n ngc ) KRA...( n thun), RN12...( n ngc ), RN22...(n thun), UN...., KSR... . Th d : DTA132 , DTC 124 vv...

* Transistor cng xut dng ( cng xut ngang )

Transistor cng xut ln thng c gi l s. S dng, S ngun vv..cc s ny c

thit k iu khin b cao p hoc bin p ngun xung hot ng , Chng thng c in


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p hot ng cao v cho dng chu ng ln. Cc s cng xut dng( Ti vi mu) thng c

u thm cc diode m trong song song vi cc CE.

S cng xut dng trong Ti vi mu

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 cs 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


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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 v

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 Bkhng

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

( cim mi P-N pha 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 ch

B => lm cho dng IBE tng hoc gim => dng ICE cng tng hoc gim , st p trn R

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 s

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 .


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3. Mt s mach 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 phnp

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.


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BI 8.

MCH KHUCH I

1. Khi nim v mch khuyh i .

Mch khuych i c s dng trong hu ht cc thit b in t, nh mch khuych im 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 hnnhiu 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 ,

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.

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 cnly 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


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* 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 v v..

b) Mach khuych i ch B.

Mch khuych i ch B l mch ch khuych i mt na chu k ca tn hiu, nukhuych 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 c

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.


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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 CL mch khuych i c in p UBE c phn c ngc vi mc ch ch ly tn hiu

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.

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 khuychi 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 .


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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 khuyc

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 uvo : 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. 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 tngng vi mass ) , Tn hiu c a vo c

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.


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- 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 t

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 )

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

Khi nim v ghp tng: Mt thit b in t gm c nhiu khi kt hp li, mi khi li c

nhiu tng khuych i c mc ni tip vi nhau v khi mc ni tip thng s dng mt

trong cc kiu ghp sau :

Ghp tng qua t in.

Ghp tng qua bin p .

Ghp tng trc tip.

Ta hy xt cc trng hp c th :


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1. Ghp tng qua t in.

* S mch ghp tng qua t in

Mch khuych i u t - c hai tng khuychi 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 dncc 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.

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.


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- 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 ph

tp v chim nhiu din tch.

2.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 Q1c ghp trc tip vi hai n cng

xut Q2 v Q3.

1. Trong cc mch khuych i ( ch A ) th phn cc nh th no l ng.

Mch khuych i c phn cc ng.


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- 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 .

1. 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 ccsai ( 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.


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- 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

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


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BI 9:

MCH N P NGUN

1. B ngun trong cc mch in t .

Trong cc mch in t ca cc thit b nh Radio -Cassette, mlpy, Ti vi mu, u VCDv v... chng s dng ngun mt chiu DC cc mc in p khc nhau, nhng ngoi zc

cm ca cc thit b ny li cm trc tip vo ngun in AC 220V 50Hz , nh vy cc thit b

in t cn c mtb phn chuyn i t ngun xoay chiu ra in p mt chiu , cung c

cho cc mch trn, b phn chuyn i bao gm :

- Bin p ngun : H th t 220V xung cc in p thp hn nh 6V, 9V, 12V, 24V v v ..

- Mch chnh lu : i in AC thnh DC.

-

Mchlc Lc gn xoay chiu sau chnh lu cho ngun DC phng hn.- Mch n p : Gi mt in p c nh cung cp cho ti tiu th

S tng qut ca mch cp ngun.

2. Mch chnh lu bn chu k .

Mch chnh lu bn chu k s dng mt Diode mc ni tip vi ti tiu th, chu k dn

=> Diode c phn cc thun do c dng in i qua diode v i qua ti, chu k m ,

Diode b phn ccngc do khng c dng qua ti.

Dng in p u ra ca mch chnh lu bn chu k.


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2. Mch chnh lu c chu k

Mch chnh lu c chu k thng dng 4 Diode mc theo hnh cu (cn gi l mch chnh

lu cu) nh hnh di.

Mch chnh lu c chu k .

- chu k dng ( u dy pha trn dng, pha di m) dng in i qua diode D1 =>

qua Rti => qua diode D4 v u dy m

- chu k m, in p trn cun th cp o chiu ( u dy trn m, di dng) dn

in i qua D2 => qua Rti => qua D3 v u dy m.

- Nh vy c hai chu k u c dng in chy qua ti.

1. Mch lc dng t in.

Sau khi chnh lu ta thu c in p mt chiu nhp nh, nu khng c t lc th in pnhp nh ny cha th dng c vo cc mch in t , do trong cc mch ngun, ta ph

lp thm cc t lc c tr s t vi trm F n vi ngn F vo sau cu Diode chnh lu.

Dngin p DC ca mch chnh lu trong hai trnghp c t v khng c t

- S trn minh ho cc trng hp mch ngun c t lc v khng c t lc.


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- Khi cng tc K m, mch chnh lu khng c t lc tham gia , v vy in p thu c c

dng nhp nh.

- Khi cng tc K ng, mch chnh lu c t C1 thamgia lc ngun , kt qu l in p u

ra c lc tng i phng, nu t C1 c in dung cng ln th in p u ra cng

bng phng, t C1 trong cc b ngun thng c tr s khong vi ngn F .

Minh ho :in dng ca t lc cng ln th in p u ra cng bng phng.

Trong cc mch chnh lu, nu c t lc m khng c ti hoc ti tiu th mt cng

xut khng ng k so vi cng xut ca bin p th in p DC thu c l DC =

1,4.AC

3. Mch chnh lu nhn 2 .

S mch ngun chnh lu nhn 2

- tr thnh mch chnh lu nhn 2 ta phi dng hai t ho cng tr s mc ni tip, sau

u 1 u ca in p xoau chiu vo im gia hai t => ta s thu c in p tng

gp 2 ln.


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- mch trn, khi cng tc K m, mch tr v dng chnh lu thng thng .

- Khi cng tc K ng, mch tr thnh mch chnh lu nhn 2, v kt qu l ta thu c i

p ra tng gp 2 ln.

1. Mch n p c nh dng Diode Zener.

.

Mch n p to p 33V c nh cung cp cho mch d knh trong Ti vi mu

- T ngun 110V khng c nh thng qua in tr hn dng R1 v gim trn Dz 33V l

ra mt in p c nh cung cp cho mch d knh

- Khi thit k mt mch n p nh trn ta cn tnh ton in tr hn dng sao cho dng in

ngc cc i qua Dz phi nh hn dng m Dz chu c, dng cc i qua Dz l khi

dng qua R2 = 0

- Nh s trn th dng cc i qua Dz bng st p trn R1 chia cho gi tr R1 , gi dng

in ny l I1 ta c

I1 = (110 - 33 ) / 7500 = 77 / 7500 ~ 10mA

Thng thng ta nn dng ngc qua Dz 25 mA

2. Mch n p c nh dng Transistor, IC n p .

Mch n p dng Diode Zener nh trn c u im l n gin nhng nhc im l cho

dng in nh ( 20mA ) . c th to ra mt in p c nh nhng cho dng in mnh

hn nhiu ln ngi ta mc thm Transistor khuych i v dng nh s di y.


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Mch n p c Transistor khuych i

- mch trn in p ti im A c th thay i v cn gn xoay chiu nhng in p ti

im B khng thay iv tng i phng.- Nguyn l n p : Thng qua in tr R1 v Dz gim c nh in p chn B ca Transisto

Q1, gi s khi in p chn E n Q1 gim => khi in p UBE tng => dng qua n

Q1 tng => lm in p chn E ca n tng , v ngc li ...

- Mch n p trn n gin v hiu qu nn c s dng rt rng di v ngi ta sn

xut cc loi IC h LA78.. thay th cho mch n p trn, IC LA78.. c s mch nh

phn mch c mu xanh ca s trn.

IC n p h LA78.. IC n p LA7805

LA7805 IC n p 5V

LA7808 IC n p 8V

LA7809 IC n p 9V

LA7812 IC n p 12V


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Lu : H IC78.. ch cho dng tiu th khong 1A tr xung, khi rp IC trong mch th U

in > Uout t 3 n 5V khi IC mi pht huy tc dng.

3. ng dng ca IC n p h 78..

IC n p h 78.. c dng rng ri trong cc b ngun , nh B ngun ca u VCD, trong

Ti vi mu, trong my tnh v v...

ng dng ca IC n p LA7805 v LA7808 trong b ngun uVCD

1. S khi ca mch n p c hi tip .

S khi ca mch n p c hi tip .

* Mt s c im ca mch n p c hi tip:

- Cung cp in p mt chiu u ra khng i trong hai trng hp in p u vo thay

i hoc dng tiu th ca ti thay i , tuy nhin s thay i ny phi c gii hn.


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- Cho in p mt chiu u ra c cht lng cao, gim thiu c hin tng gn xoay

chiu.

- Nguyn tc hot ng ca mch.

- Mch ly mu s theo di in p u ra thng qua mt cu phn p to ra ( Ulm : p ly

mu)

- Mch to p chun => gim ly mt mc in p c nh (Uc : p chun )

- Mch so snh s so snh hai in p ly mu Ulm v p chun Uc to thnh in p i

khin.

- Mch khuch i sa sai s khuch i p iu khin, sau a v iu chnh s hot

ng ca n cng xut theo hng ngc li, nu in p ra tng => thng qua mch hi

tip iu chnh => n cng xut dn gim =>in p ra gim xung . Ngc li nu in

p ra gim => thng qua mch hi tip iu chnh => n cng xut li dn tng => v i

p ra tng ln =>> kt qu in p u ra khng thay i.

2. Phn tch hot ng ca mch ngun c hi tip trong Ti vi en trng Samsung

in p u vo cn gn xoay chiu in p u ra bng phng

Mch n p tuyn tnh trong Ti vi Samsung en trng .

* ngha cc linh kin trn s .

- T 2200F l t lc ngun chnh, lc in p sau chnh lu 18V , y cng l in p u

vo ca mch n p, in p ny c th tng gim khong 15%.


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- Q1 l n cng xut ngun cung cp dng in chnh cho ti , in p u ra ca mc n

ly t chn C n Q1 v c gi tr 12V c nh .

- R1 l tr phn dng c cng xut ln ghnh bt mt phn dng in i qua n cng xut

- Cu phn p R5, VR1 v R6 to ra p ly mu a vo chn B n Q2 .

- Diode zener Dz v R4 to mt in p chun c nh so vi in p ra.

- Q2 l n so snh v khuych i in p sai lch => a v iu khins hot ng ca

n cng xut Q1.

- R3 lin lc gia Q1 v Q2, R2 phn p cho Q1

* Nguyn l hot ng .

- in p u ra s c xu hng thay i khi in p u vo thay i, hoc dng tiu th

thay i.

- Gi s : Khi in p vo tng => in p ratng => in p chn E n Q2 tng nhiu h

chn B ( do c Dz gim t chn E n Q2 ln Ura, cn Ulm ch ly mt phn Ura ) do UBE gim => n Q2 dn gim => n Q1 dn gim => in p ra gim xung. Tng t

khi Uvo gim, thng qua mch iu chnh =>ta li thu c Ura tng. Thi gian iu

chnh ca vng hi tip rt nhanh khong vi giy v c cc t lc u ra loi b,

khng lm nh hng n cht lng ca in p mt chiu => kt qu l in p u ra

tng i phng.

- Khi iu chnh bin tr VR1 , in p ly mu thay i, dn n Q2 thay i , dn

n Q1 thay i => kt qu l in p ra thay i, VR1 dng iu chnh in p ra theo

mun .

3. Mch ngun Ti vi ni a nht.

S mch ngun n p tuyn tnh trong Ti vi mu ni a Nht .


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- C1 l t lc ngun chnh sau cu Diode chnh lu.

- C2 l t lc u ra ca mch ngun tuyn tnh.

- Cu phn p R4, VR1, R5to ra in p ly mu ULM

- R2 v Dz to ra p chun Uc

- R3 lin lc gia Q3 v Q2, R1 nh thin cho n cng xut Q1

- R6 l in tr phn dng, l in tr cng xut ln .

- Q3 l n so snh v khuch i p d sai

- Khuch i in p d sai

- Q1 n cng xut ngun

- => Ngun lm vic trong di in p vo c th thay i 10%,in p ra lun lun c n


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BI 10.

MACH TO DAO NG

1. Khi nim v mch dao ng.

Mch dao ng c ng dng rt nhiu trong cc thit b in t, nh mchdao ng nitrong khi RF Radio, trong b knh Ti vi mu, Mch dao ng to xung dng , xung mnh

trong Ti vi , to sng hnh sin cho IC Vi x l hot ng v v...

- Mch dao ng hnh Sin

- Mch dao ng a hi

- Mch dao ng nght

- Mch dao ng dng IC

2. Mch dao ng hnh Sin

Ngi ta c th to dao ng hnh Sin t cc linh kin L - C hoc t thch anh.

* Mch dao ng hnh Sin dng L - C

Mch dao ng hnh Sin dng L - C

- Mach dao ng trn c t C1 // L1 to thnh mch dao ng L -C duy tr s dao ng

ny th tn hiu dao ng c a vo chn B ca Transistor, R1 l tr nh thin cho

Transistor, R2 l tr gnh ly ra tn hiu dao ng ra , cun dy u t chn E


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Transistor xung mass c tc dng ly hi tip duy tr dao ng. Tn s dao ng ca

mch ph thuc vo C1 v L1 theo cng thc

- f = 1 / 2. .( L1.C1 ) 1/2

* Mch dao ng hnh sin dng thch anh.

Mch to dao ng bng thch anh .

- X1 : l thch anh to dao ng , tn s dao ng c ghi trn thn ca thach anh, khi

thch anh c cp in th n t dao ng ra sng hnh sin.thch anh thng c tn s da

ng t vi trm KHz n vi chc MHz.

- n Q1 khuych i tn hiu dao ng t thch anh v cui cng tn hiu c ly ra

chn C.

- R1 va l in tr cp ngun cho thch anh va nh thin cho n Q1

- R2 l tr ghnh to ra st p ly ra tn hiu .

Thch anh dao ng trong Tivi mu, my tnh


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3. Mch dao ng a hi.

Mch dao ng a hi to xung vung

* Bn c th t lp s trn vi cc thng s nh sau :

- R1 = R4 = 1 K ohm- R2 = R3 = 100K ohm

- C1 = C2 = 10F/16V

- Q1 = Q2 = n C828

- Hai n Led

- NgunVcc l 6V DC

- Tng gi thnh lnh kin ht khong 6.000 VN

* Gii thch nguyn l hot ng: Khi cp ngun , gi s n Q1 dn trc, p Uc n Qgim => thng qua C1 lm p Ub n Q2 gim => Q2 tt => p Uc n Q2 tng => thng qu

C2 lm p Ub n Q1 tng => xc lp trng thi Q1 dn bo ho v Q2 tt , sau khong thi

gian t , dng np qua R3 vo t C1 khi in p ny > 0,6V th n Q2 dn => p Uc n Q2

gim => tip tc nh vy cho n khi Q2 dn bo ho v Q1 tt, trng thi lp i lp li v t

thnh dao ng, chu k dao ng ph thuc vo C1, C2 v R2, R3.


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1. IC to dao ng XX555 ; XX c th l TA hoc LA v v ...

Mch dao ng to xung bng IC 555

- Bn hy mua mt IC h 555 v t lp cho mnh mt mch to dao ng theo s nguy

l nh trn.

- Vcc cung cp cho IC c th s dng t 4,5V n 15V , ng mch mu l dng

ngun, mch mu en di cng l m ngun.

- T 103 (10nF) t chn 5 xung mass l c nh v bn c th b qua ( khng lp cng

c )

- Khi thay i cc in tr R1, R2 v gi tr t C1 bn s thu c dao ng c tn s v

rng xung theo mun theo cng thc.

T = 0.7 (R1 + 2R2) C1 v f =1.4

(R1 + 2R2) C1

T = Thi gian ca mt chu k ton phn tnh bng (s)

f = Tn s dao ng tnh bng (Hz)R1 = in tr tnh bng ohm

R2 = in tr tnh bng ohm

C1 = T in tnh bng Fara


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T = Tm + Ts T : chu k ton phn

Tm = 0,7 x ( R1 + R2 ) x C1 Tm : thi gian in mc cao

Ts = 0,7 x R2 x C1 Ts : thi gian in mc thp

Chu k ton phn T bao gm thi gian c in mc cao Tm v thi gian c in mc thp Ts

- T cc cng thc trn ta c th to ra mt dao ng xung vung c rng Tm v Ts bt

k.

- Sau khi to ra xung c Tm v Ts ta c T = Tm + Ts v f = 1/ T

* Th d bn thit k mch to xung nh hnh di y.

Mch to xung c Tm = 0,1s , Ts = 1s

Bi tp : Lp mch dao ng trn vi cc thng s :

C1 = 10F = 10 x 10-6 = 10-5 F

R1 = R2 = 100K = 100 x 103

Tnh Ts v Tm = ? Tnh tn s f = ?

Bi lm :


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Ta c Ts = 0,7 x R2 x C1 = 0,7 x 100.103x 10-5 = 0,7 s

Tm = 0,7 x ( R1 + R2 ) x C1 =

= 0,7 x 200.103 x 105 = 1,4 s

=> T = Tm + Ts = 1,4s + 0,7s = 2,1s

=> f =1 / T = 1/2,1 ~ 0,5 Hz

1. Mch dao ng nght ( Blocking OSC )

Mh dao ng nght c nguyn tc hot ng kh n gin, mch c s dng rng ri

trong cc b ngun xung ( switching ), mch c cu to nh sau :

Mch dao ng nght

Mch dao ng nght bao gm :

- Bin p : Gm cun s cp 1-2 v cun hi tip 3-4, cun th cp 5-6

- Transistor Q tham gia dao ng v ng vai tr l n cng xut ngt m to ra dng in

bin thin qua cun s cp.

- Tr nh thin R1 ( l in tr mi )

- R2, C2 l in tr v t in hi tip

C hai kiu mc hi tip l hi tip dng v hi tip m, ta xt cu to v nguyn tc ho

ng ca tng mch.


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* Mch dao ng nght hi tip m .

- Mch hi tip m c cun hi tip 3-4 qun ngc chiu vi cun s cp 1-2 , v in tr

mi R1 c tr s nh khong 100K , mch thng c s dng trong cc b ngun

cng xut nh khong 20W tr xung

- Nguyn tc hot ng : Khi cp ngun, dng nh thin qua R1 kch cho n Q1 dn kh

mnh, dng qua cun s cp 1-2 tng nhanh to ra t trng bin thin => cm ng sang

cun hi tip, chiu m ca cun hi tip c a v chn B n Q thng qua R2, C2 lm

in p chn B n Q gim < 0V => n Q lp tc chuyn sang trng thi ngt, sau

khong thi gian t dng in qua R1 np vo t C2 lm p chn B n Q tng => n Q

dn lp li chu k th hai => to thnh dao ng .

- Mch dao ng nght hi tip m c u im l dao ng nhanh, nhng c nhc im d

b xc in lm hng n Q do mch thng khng s dng trong cc b ngun cngxut ln.

* Mch dao ng nght hi tip dng .

- Mch dao ng nght hi tip dng c cun hi tip 3-4 qun thun chiu vi cun s c

1-2, in tr mi R1 c tr s ln khong 470K

- V R1 c tr s ln, ln dng nh thin qua R1 ban u nh => n Q dn tng dn =>

sinh ra t trng bin thin cm ng ln cun hi tip => in p hi tip ly chiu dng

hi tip qua R2, C2 lm n Q dn tng => v tip tc cho n khi n Q dn bo ho, Kn Q dn bo ho, dng in qua cun 1-2 khng i => mt in p hi tip => p chn

B n Q gim nhanh v n Q lp tc chuyn sang trng thi ngt, chu k th hai lp li

nh trng thi ban u v to thnh dao ng.

- Mch ny c u im l rt an ton dao ng t t khng b xc in, v c s dng

trong cc mch ngun cng xut ln nh ngun Ti vimu.


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* Xem li l thuy v cm ng in t :

Th nghim v hin tng cm ng in t trong bin p.

th nghim trn ta thy rng , bng n c

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