Bao Cao Thuc Tap Dien Tu

8/3/2019 Bao Cao Thuc Tap Dien Tu

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Phng th nghim in- in t GVHD: Nguyn Kiu Tam

TNG LIN ON LAO NG VIT NAM

TRNG I HC TN C THNG

GVHD : NGUYN KIU TAM

H V TN : NGUYN VN DUNLP : 07DD3DMSSV : 070571D

TP.H CH MINH NM 2010

- -


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LI M U

Hin nay trong thi k Cng Nghip Ha - Hin i Ha t nc, in

in T gi vai tr then cht trong cc ngnh, bt k ngnh no

cng u cn n in in T, do vy nn vic hc tp,

nghin cu hiu su hn v in in T l vic lm ht sc

quan trng i vi bt k mt Sinh Vin ngnh in no.

Bn cnh vic lm vng l thuyt th Thc Hnh lm thc t cng

rt quan trng, n khng ch i hi ngi hc c vn kin thc v

l thuyt vng chc, m n i hi ngi lm phi c k nng v s

sng to. Trong sut thi gian hc mn Thc Tp in T vi s

dn dt nhit tnh v ci m ca thy Nguyn Kiu Tam, gip em

hc hi c rt nhiu iu b ch, gip em nm chc v hiu su

hn v phn l thuyt c hc trn lp, thng qua nhng bui

lm nhng mch in t n gin, gip cho em hiu c bn v

cc mch in t v cch lm ra cc mch in t nh th no, ium t trc ti gi, khng ch em m bt k bn no khi cha tri qua

thc hnh th u m h v cc mch in t v lm cch no lm ra

c chng. V iu thc mc ny c gii p sau nhng bui thc

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hnh .

Qua nhng bui thc hnh ny gip cho em lm quen vi

nhng vic lm thc t, cho em nhng kinh nghim, k nng thc

hnh v lm vic theo nhm mt cch c hiu qu nht.

Cun bo co ny l ton b qu trnh hc tp, nghin cu c l

thuyt v thc hnh m em hc trong thi gian qua.

Do kinh nghim cha nhiu nn khng th chnh khi thiu xt, em

rt mong nhn c kin ng gp ca thy v cc bn v bi Bo

Co ny.

Em xin chn thnh cm n !

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A. L THUYT

Gii Thiu V Cc Linh Kin in TI. in Tr

1. Khi nim v in tr.

in tr l g ? Ta hiu mt cch n gin in tr l s cn tr dng in camt vt dn in, nu mt vt dn in tt th in tr nh, vt dn in km thin tr ln, vt cch in 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 tnhtheo 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 quantrng, chng c lm t hp cht cacbon v kim loi tu theo t l pha trn mngi ta to ra c cc loi in tr c tr s khc nhau.

Hnh dng ca in tr trong thit b in t.

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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 1M = 1000 K = 1000.000

b) 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 trnthn. 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 tr Mu sc Gi tren 0 Xanh l 5

Nu 1 Xanh l 6 2 Tm 7

Cam 3 Xm 8

Vng 4 Trng 9Nh vng -1Nh bc -2

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in tr thng c k hiu bng 4 vng mu , in tr chnh xc th k hiubng 5 vng mu.

* Cch c tr s in tr 4 vng mu :

Cch c in tr 4 vng mu

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Vng s 4 l vng cui lun lun c mu nh vng hay nh bc, y lvng 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. 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 sais c nhiu mu, do gy kh khn cho ta khi xc inh u l vng cuicng, 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 hngn v.

Tr s = (vng 1)(vng 2)(vng 3) x 10 ( m vng 4)

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

4 Thc hnh c tr s in tr.

Cc in tr khc nhau vng mu th 3

Khi cc in tr khc nhau vng mu th 3, th ta thy vng mu bi sny thng thay i t mu nh bc cho n mu xanh l , tng ng viin 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 mus 3 thay i th cc gi tr in tr trn tng gim 10 ln.

5 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 rakhong 150 loi tr s in tr thng dng , bng di y l mu sc v tr s cacc in tr thng dng.

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Cc gi tr in tr thng dng.

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6 -. Phn loi in tr.

in tr thng : in tr thng l cc in tr c cng xut nh t0,125W n 0,5W

in tr cng xut: L cc in tr c cng xut ln 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

7 Cng xut ca in tr.

Khi mc in tr vo mt on mch, bn thn in tr tiu th mt cng xut Ptnh 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 vodng in i qua 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 xut m n s tiu th.

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in tr chy do qu cng xut

s trn cho ta thy : Ngun Vcc l 12V, cc in tr u c tr s l120 nhng c cng xut khc nhau, khi cc cng tc K1 v K2 ng, ccin 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 intr khng chy.

Khi K2 ng, in tr c cng xut nh hn cng xut tiu th , nn in tr

b chy .

8 Bin tr, trit p :Bin trL in tr c th chnh thay i gi tr, c k hiu l VR chng chnh dng 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 kthut vin, bin tr c cu to nh hnh bn di.

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Cu to ca bin tr

Trit p : Trit p cng tng t bin tr nhng c thm cn chnh v thng btr 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 tutheo mc chnh.

K hiu trit p trn s nguyn l.

Hnh dng trit p Cu to trong trit p

9 in tr mc ni tip .

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in tr mc ni tip.

Cc in tr mc ni tip c gi tr tng ng bng tng cc in tr thnhphn cng li. Rtd = R1 + R2 + R3

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 tr int tr .

10 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 (1 / Rtd) = (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 intr .I1 = ( U / R1) , I2 = ( U / R2) , I3 =( U / R3 )

in p trn cc in tr mc song song lun bng nhau

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11 in tr mc hn hp

in tr mc hn hp.

Mc hn hp cc in tr to ra in tr ti u hn . V d: nu ta cn mt in tr 9K ta c th mc 2 in tr 15K song song sau

mc ni tip vi in tr 1,5K .

12 ng dng ca in trin tr c mt mi ni trong thit b in t v nh vy in tr l linh kinquan 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 c ngun 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 nhsau: 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 trcn tm 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

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Mc in tr thnh cu phn p c c mt in p theo mun tmt in p cho trc.

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 U1ph thuc vo gi tr hai in tr R1 v R2.theo cng thc .

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

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 ng R C

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Mch to dao ng s dng IC 555

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II. T in (capacitor)

T in : T in l linh kin in t th ng c s dng rt rng ri trong ccmch in t, chng c s dng trong cc mch lc ngun, lc nhiu, mch

truyn tn hiu xoay chiu, mch 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 gil in mi.

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

Cu to t gm Cu to t ho

2. Hnh dng thc t ca t in.

Hnh dng ca t gm.

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Hnh dng ca t ho

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 miv khong cch gi 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 thct thng dng cc n v nh hn nh MicroFara (F) , NanoFara (nF), PicoFara(pF).

1 Fara = 1.000.000 Fara = 1.000.000.000 n F = 1.000.000.000.000 p F

1 Fara = 1.000 n Fara 1 n Fara = 1.000 p Fara

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

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K hiu ca t in trn s nguyn l.

4 . S phng np ca t in .

Mt tnh cht quan trng ca t in l tnh cht phng np ca t , nh tnh chtny m t c kh nng dn in xoay chiu.

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 int ngun U i qua bng n np vo t, dng np ny lm bng n lo sng,khi t np y th 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 thdng in t cc dng (+) ca t phng qua bng n v cc m (-) lm bng nlo sng, khi t phng ht in th bng n tt.

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

5 . 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

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 10 4 = 470000p ( Ly n v l pic Fara)= 470 n Fara = 0,47 F

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

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* 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 lyn v l MicroFara

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

6. ngha 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 trin dung, y chnh l gi tr in p cc i m t chu c, qu in pny t s b n.

Khi lp t vo trong mt mch in c in p l U th bao gi ngi ta cnglp t in 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..

7 Phn loi t in

7.1) 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 Ftr xung, cc t ny thng c s dng trong cc mch in c tn s cao hocmch lc nhiu.

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T gm l t khng phn cc.

7.2) 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 0,47Fn khong 4.700 F , t ho thng c s dng trong cc mch c tn s thphoc dng lc ngun, t ho lun lun c hnh tr..

T ho L t c phn cc m dng.

7.3) T xoay .T xoay l t c th xoay thay i gi tr in dung, t ny thng

c lp trong Radio thay i tn s cng hng khi ta d i.

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T xoay s dng trong Radio

8 Phng php kim tra t in

8.1) o kim tra t giy v t gm.

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

o kim tra t giy hoc t gm .

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hnh nh trn l php o kim tra t gm, c ba t C1 , C2 v C3 c indung bng nhau, trong C1 l t tt, C2 l t b d v C3 l t b chp.

Khi o t C1 ( T tt ) kim phng ln 1 cht ri tr v v tr c. ( Lu cct 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 likhng tr v v 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.

8.2) o kim tra t ho

T ho t khi b d hay b chp nh t giy, nhng chng li hay hng dng bkh ( kh ho cht bn trong lp in mi ) lm in dung ca t b gim , kim

tra t ho , ta thng so snh phng np ca t vi mt t cn tt c cng indung, hnh nh di y minh ho 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 C1 cn 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.

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Nu hai t phng np bng nhau l t cn kim tra cn tt, trn ta thy tC2 phng np 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 chnt khi mch in, sau kim tra nh trn.

9 Cc kiu mc v ng dng

9.1 . T in mc ni tip .

Cc t in mc ni tip c in dung tng ng C t c tnh bi cngthc : 1 / C 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 pca 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 t trc phi ni vi cc dng t sau:

T in mc ni tip T in mc song song

9.2 T in mc song song. Cc t in mc song song th c in dung tng ng bng tng in

dung ca cc t 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.

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9.3 ng dng ca t in .

T in c s dng rt nhiu trong k thut in v in t, trong cc thit bin t, t in l mt linh kin khng th thiu c, mi mch in t u c mtcng dng nht nh nh truyn dn tn hiu , lc nhiu, lc in ngun, to daong ..vv

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

* 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 sau khi chnh lu c bng phng cung cp cho ti tiu th, tathy nu khng c t th p DC sau i t l in p nhp nh, khi c t inp ny c lc tng i phng, 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

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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.

Phn loi t in v cch c gi tr

Mt t in l mt linh kin in t th ng to bi hai b mt dn in cngn cch bi in mi. Khi c chnh lch in th ti hai b mt, ti cc b mt sxut hin in tch cng cng , nhng tri du.

S tch t ca in tch trn hai b mt to ra kh nng tch tr nng lng intrng ca t in. Khi chnh lch in th trn hai b mt l in th xoay chiu,s tch lu in tch b chm pha so vi in p, to nn tr khng ca t in trongmch in xoay chiu.

V mt lu tr nng lng, t in c phn ging vi c-quy. Mc d cch hotng ca chng th hon ton khc nhau, nhng chng u cng lu tr nng lngin. c qui c 2 cc, bn trong xy ra phn ng ha hc to ra electron ccny v chuyn electron sang cc cn li. T in th n gin hn, n khng th tora electron - n ch lu tr chng. T in c kh nng np v x rt nhanh. y l

mt u th ca n so vi c qui.

T in: SMD ceramic pha trn bn tri;SMD tantali pha di bn tri;

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through-hole tantali pha trn bn phi;through-hole electrolytic pha di bn phi.

T l phn chia trn thc l cm

T in theo ng tn gi chnh l linh kin c chc nng tch t nng lng in,ni mt cch nm na. Chng thng c dng kt hp vi cc in tr trong ccmch nh thi bi kh nng tch t nng lng in trong mt khong thi giannht nh. ng thi t in cng c s dng trong cc ngun in vi chcnng lm gim gn sng ca ngun trong cc ngun xoay chiu, hay trong ccmch lc bi chc nng ca t ni mt cch n gin l t ngn mch (cho dngin i qua) i vi dng in xoay chiu v h mch i vi dng in 1 chiu.

Trong mt s cc mch in n gin, n gin ha trong qu trnh tnh tonhay thay th tng ng th chng ta thng thay th mt t in bng mt dy

dn khi c dng xoay chiu i qua hay tho t ra khi mch khi c dng mt chiutrong mch. iu ny kh l cn thit khi thc hin tnh ton hay xc nh cc s mch tng ng cho cc mch in t thng thng.

Hin nay, trn th gii c rt nhiu loi t in khc nhau nhng v c bn, chngta c th chia t in thnh hai loi: T c phn cc (c cc xc nh) v t inkhng phn cc (khng xc nh cc dng m c th).

c trng cho kh nng tch tr nng lng in ca t in, ngi ta a rakhi nim l in dung ca t in. in dung cng cao th kh nng tch tr nng

lng ca t in cng ln v ngc li. Gi tr in dung c o bng n vFarad (k hiu l F). Gi tr F l rt ln nn thng thng trong cc mch in t,cc gi tr t ch o bng cc gi tr nh hn nh micro fara (F), nano Fara (nF)hay picro Fara (pF).

1F=106F=109nF=1012pF

T ho

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K hiu t ho v hnh dng t ho

T ha l mt loi t c phn cc. Chnh v th khi s dng t ha yu cu ngis dng phi cm ng chn ca t in vi in p cung cp. Thng thng, ccloi t ha thng c k hiu chn c th cho ngi s dng bng cc k hiu +hoc = tng ng vi chn t.

C hai dng t ha thng thng l t ha c chn ti hai u tr trn ca t (tc ghi 220F trn hnh a) v loi t ha c 2 chn ni ra cng 1 u tr trn (t cghi gi tr 10F trn hnh a). ng thi trn cc t ha, ngi ta thng ghi kmgi tr in p cc i m t c th chu c. Nu trng hp in p ln hn sovi gi tr in p trn t th t s b phng hoc n t ty thuc vo gi tr in pcung cp. Thng thng, khi chn cc loi t ha ny ngi ta thng chn ccloi t c gi tr in p ln hn cc gi tr in p i qua t m bo t hot

ng tt v m bo tui th ca t ha.

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T Tantali

T Tantali

T Tantali cng l loi t ha nhng c in p thp hn so vi t ha. Chng kht nhng nh v chng c dng khi yu cu v t dung ln nhng kch thcnh.

Cc loi t Tantali hin nay thng ghi r trn n gi tr t, in p cng nh ccca t. Cc loi t Tantali ngy xa s dng m mu phn bit. Chng thngc 3 ct mu (biu din gi tr t, mt ct biu din gi tr in p) v mt chmmu c trng cho s cc s khng sau du phy tnh theo gi tr F. Chng cngdng m mu chun cho vic nh ngha cc gi tr nhng i vi cc im mu thim mu xm c ngha l gi tr t nhn vi 0,01; trng nhn 0,1 v en l nhn 1.Ct mu nh ngha gi tr in p thng nm gn chn ca t v c cc gi trnh sau:

Vng=6,3V

en= 10VXanh l cy= 16V

Xanh da tri= 20V

Xm= 25V

Trng= 30V

Hng= 35V

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T khng phn cc

T thng v k hiu

Cc loi t nh thng khng phn cc. Cc loi t ny thng chu c cc inp cao m thng thng l khong 50V hay 250V. Cc loi t khng phn cc nyc rt nhiu loi v c rt nhiu cc h thng chun c gi tr khc nhau.

Rt nhiu cc loi t c gi tr nh c ghi thng ra ngoi m khng cn c h snhn no, nhng cng c cc loi t c thm cc gi tr cho h s nhn. V d ccc t ghi 0.1 c ngha gi tr ca n l 0,1F=100nF hay c cc t ghi l 4n7 th cngha gi tr ca t chnh l 4,7nF

Cc loi t c dng m

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M s thng c dng cho cc loi t c gi tr nh trong cc gi tr cnh ngha ln lt nh sau:

- Gi tr th 1 l s hng chc

- Gi tr th 2 l s hng n v

- Gi tr th 3 l s s khng ni tip theo gi tr ca s to t gi tr 1 v 2.Gitr ca t c c theo chun l gi tr picro Fara (pF)

- Ch s i km sau cng l ch gi tr sai s ca t.

V d: t ghi gi tr 102 th c ngha l 10 v thm 2 s 0 ng sau =1000pF = 1nFch khng phi 102pF

Hoc v d t 272J th c ngha l 2700pF=2,7nF v sai s l 5%

T c dng m mu

T dng m mu

S dng ch yu trn cc t loi polyester trong rt nhiu nm. Hin nay cc loi t

ny khng cn bn trn th trng na nhng chng vn tn ti trong kh nhiucc mch in t c. Mu c nh ngha cng tng t nh i vi mu trn intr. 3 mu trn cng ln lt ch gi tr t tnh theo pF, mu th 4 l ch dung sai vmu th 5 ch ra gi tr in p.

V d t c mu nu/en/cam c ngha l 10000pF= 10nF= 0.01uF.

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Ch rng ko c khong trng no gia cc mu nn thc t khi c 2 mu cnhnhau ging nhau th n to ra mt mng mu rng. V d Di rng/vng=220nF=0.22uF

T Polyester

Ngy nay, loi t ny cng him khi c s dng. Gi tr ca cc loi t nythng c in ngay trn t theo gi tr pF. T ny c mt nhc im l d bhng do nhit hn nng. Chnh v th khi hn cc loi t ny ngi ta thng ccc k thut ring thc hin hn, trnh lm hng t.

T polyester

T in bin iT in bin i thng c s dng trong cc mch iu chnh radio v chngthng c gi l t xoay. Chng thng c cc gi tr rt nh, thng thng nmtrong khong t 100pF n 500pF.

T xoay

Rt nhiu cc t xoay c vng xoay ngn nn chng khng ph hp cho cc dibin i rng nh l in tr hoc cc chuyn mch xoay. Chnh v th trong nhiung dng, c bit l trong cc mch nh thi hay cc mch iu chnh thi gianth ngi ta thng thay cc t xoay bng cc in tr xoay v kt hp vi 1 gi trt in xc nh.

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T chnT chn l cc t xoay c gi tr rt nh. Chng thng c gn trc tip ln bnmch in t v iu chnh sau khi mch c ch to xong. Tng t cc bintr hin ny th khi iu chnh cc t chn ny ngi ta cng dng cc tuc n vt

loi nh iu chnh. Tuy nhin do gi tr cc t ny kh nh nn khi iu chnh,ngi ta thng phi rt cn thn v kin tr v trong qu trnh iu chnh c s nhhng ca tay v tuc-n-vt ti gi tr t.

T chnCc t chn ny thng c gi tr rt nh, thng thng nh hn khong 100pF. Ciu c bit l khng th gim nh c cc gi tr t chn v 0 nn chng thngc ch nh vi cc gi tr t in ti thiu, khong t 2 ti 10 pF

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III. Cun Cm ( Inductor )

1. Cu to ca cun cm.

Cun cm gm mt s vng dy qun li thnh nhiu vng, dy qun c snemay cch in, li cun dy c th l khng kh, hoc l vt liu dn t nhFerrite hay li thp k thut .

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 cundy 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 khic dng in bin thin chy qua.

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

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

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n : l s vng dy ca cun dy.

l : l chiu di ca cun dy tnh bng mt (m)

S : l tit din ca li, tnh bng m2

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 cacun dy i vi dng in xoay chiu .

ZL = 2.3,14.f.L

Trong : ZL l cm khng, n v l

f : l tn s n v l Hz

L : l h s t cm , n v l Henry

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 uvo cc ngun in 12V nhng c tn s khc nhau thng qua cc cng tc K1,K2 , K3 , khi K1 ng 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 quacun dy yy hn ( do ZL tng ) => bng n sng yu i, khi K3 ng , dngin xoay chiu 200Hz i qua cun dy yu nht ( do ZL tng cao nht) => bngn sng yu nht.

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=> Kt lun : Cm khng ca cun dy t l vi h s t cm ca cun dy v tl vi tn s dng in xoay chiu, ngha l dng in xoay chiu c tn s cngcao th i qua cun dy cng kh, dng in mt chiu c tn s f = 0 Hz v vyvi 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 vnnng, thng thng cun dy c phm cht tt th in tr thun phi tng inh so vi cm khng, in tr thun cn gi l in tr tn hao v chnh in trny sinh ra nhit khi cun dy hot 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.I 2 / 2

W : nng lng ( June )

L : H s t cm ( H )

I dng in.

Th nghim v tnh np x ca cun dy.

th nghim trn : Khi K1 ng, dng in qua cun dy tng dn ( do cun dysinh ra cm khng chng li dng in tng t ngt ) v vy bng n sng t t,khi K1 va ngt v K2 ng , nng lng np trong cun dy to thnh in p

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cm ng phng ngc li qua bng n lm bng n lo sng => l hintng cun dy x in.

Cun Dy l mt linh kin in t th ng l thuc vo tn s to t mt dy dn invi vi vng qun. Mt cng c sanh t khi mc ni vi in.

Cun dy c biu tng mch in c mt T Cm L obng n v Hen Ry (H)

Tnh Cht in DC

Dng in Mt Chiu l dng in c cng khng i v khng l thuc vo tns. i vi dng in mt chiu, Cun dy hot ng nh mt in tr c in khng

bng khng hay ni khc hn Cun dy Ni Mch

Tnh Cht in AC

Khi mc in AC vi cun dy, dng in trn cun dy sinh ra mt in Trng, E.Thay i ca in trng trong cc vng qun ca cun dy sinh ra mt T Trng, B,vung gc vi in Trng

T Trng

T trng sn sinh t l vi T Dung v Dng in

B = I L

Khi dng in bng khng, B = 0. Vy khi c dng in th c t khi khng c dngin th khng c t

Khi Cun dy dn in vi I 0 cun dy s tr thnh Nam Chm in.

T Dung

T Dung l tnh cht Vt l ca cun dy, c k hiu L, o bng n v Henry - H

T Dung t l thun vi Chiu di, S vng qun bnh phng v t l nghch vi dintch b mt ca cun dy

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T Dung, L, l kh nng sn sinh t ca cun dy bi mt dng in bng t l T SnSinh trn Dng in

in Th

Thay i t theo thi gian to mt in th trn cun dy V_L c chiu cng chiu vi

dng in to ra T trng

Dng in

in Khng

V mi vt dn in u c in Tr R nn

Theo Tn s thi gian

Z = R + XLZ = R + j L

Theo Gc

Z = |R|/_Z = [(RL)2 + (L)2] /_Tan-1 L / RL

Phn ng Tn S

Cun dy l mt cng c l thuc tn s

= 0, XL = 0, I 0. Cun dy ng Mch = 00, XL = 00, I = 0. Cun dy H Mch = RL / L, XL = RL, I = V / 2 RL.

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Vi Dng in ti ba im tn s thi gian c th v th I - f

Gc Gia in th v Dng in

Trong trng hp cun dy khng c in tr, in th i trc dng in mt gc 90.

Trong trng hp cun dy c in tr, in th i trc dng in mt gc

Tan = = 2

Khi i Gc , Tn s thi gian, T Dung, in Tr cng thay i

f = (Tan / 2) (RL / L)

V t = 1 / f

t = (2 / Tan) (L / RL )

Nng Lng Lu Tr

Nng Lng Lu Tr trn cun dy bng kh nng ca Dng in to t

Ch S Cht Lng

Hiu sut lm vic ca cun dy c biu th qua Ch S Cht Lng, Q. Ch S ChtLng c nh ngha l t s ca in ng trn in Khng

in t Cm

T trn cc vng qun N ca cun dy c t dung L

= N B

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-

Thay i t trn cc vng qun theo thi gian to mt in th trn cc vng qun cacun dy c chiu ngc chiu vi dng in to ra T trng

Phng Php Ni Kt

Nhiu Cun Dy c th mc ni tip vi nhau tng T Dung hay song song vi nhaud gim T Dung

Ni Tip

Khi mc ni tip nhiu cun dy li vi nhau, tng t dung s tng v bng tng ca cct dung

Lt = L1 + L2 + Ln

Khi mc ni tip 2 cun dy cng gi tr t dung, tng t dung s tng gp i

Lt = L + L = 2L

Song Song

Khi mc song song nhiu t dung li vi nhau, tng t dung s gim v bng Tch cacc t dung trn tng ca cc t dung

200px

Khi mc song song 2 cun dy cng gi tr t dung, tng t dung s bng mt na tdung ca cun dy

Lt = (L L) / (L + L) = L

Cch c gi tr cun cm thng qua m mu:

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Tng t nh i vi in tr, trn th gii c mt s loi cun cm c cu trc tngt nh in tr. Quy nh mu v cch c mu u tng t nh i vi cc in tr.

Tuy nhin, do cc gi tr ca cc cun cm thng kh linh ng i vi yu cu thitk mch cho nn cc cun cm thng c tnh ton v qun theo s vng dy xcnh. Vi mi loi dy, vi mi loi li khc nhau th gi tr cun cm s khc nhau.Trong phn gio trnh ny khng cp c th ti cch tnh ton v qun cc cun cmkhc nhau. Phn ny s c cp c th trong phn sch sau ny.

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4. ng dng ca cun cm

a) Loa (speaker)

Loa l mt ng dng ca cun dy v t trng

- Cu to ca loa: Loa gm mt nam chm hnh tr c hai cc lngvo nhau, cc N gia v cc S xung quanh, gia hai cc to thnhmt khe t c t trng kh mnh, mt cun dy c gn vi mngloa t trong khe t, mng loa c bng chn cao su mm, gipcho 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=> 20.000 HZ ) 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 chocun dy dao ng => mng loa dao ng theo v pht ra m thanh.- ch : tuyt i khng a dng in mt chiu vo loa, v dngin mt chiu ch to ra t trng c nh, v cun dy ca loa chdao ng lch v mt hng ri dng lai, khi dng mt chiu quacun dy tng mnh ( do khng c in p cm ng theo chiu ngclai ) v vy cun dy s b chy.

b) Micro

Thc cht cu to ca micro l mt chic loa thu nh,v cu to microging loa nhng c s vng cung trn cun dy ln hn loa rtnhiu,v vy tr khng ca cun dy micro l rt ln khong 600

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( tr khng loa t 4 n 16 ) ngoi ra mng micro cng c cu to rtmng c th d dng dao ng khi c m thanh tc ng vo .Loa l thit b chuyn i dng in thnh m thanh, cn micro th ngc li,chuyn m thanh thnh dng in m tn.

c) Rle ( Relay )

R le cng l mt ng dng ca cun dy trong sn xut linh kinin t, nguyn l hot ng ca r le l bin i dng in thnh ttrng thng qua cun dy, t trng li to thnh lc c hc thngqua lc ht thc hin mt ng tc v c kh nh ng m cngtc, ng m hnh trnh ca mt thit b t ng

d) Bin p

- Bin p ngun:

Bin p ngun thng gp trong cassete, amply bin p ny hot ng li in pc tn s 50 hz, l bin p s dng cc l Tnsilic hnh ch E v ch I ghp li, bin pny c t s vng/ volt ln.

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Bin p m tn s dng lm bin p v bin p ra loa trong cc mch khuch i cngsut, bin p cng s dng nhng l tnsilic lm li, nhng mng hn trnh tn hao,

bin p m tn hot ng tn s cao hn, v vy c s vng/ volt thp hn. Khi thitk bin p m tn ngi ta thng ly tn s trung binh t 1 khz n 3 khz.- Bin p xung v cao p

Bin p xung l bin p hot ng tn s cao vi chc khz nh bin p trong cc bngun xung,bin p cao p, li bin p xung lm bng ferit, do hot ng tn s caonn bin p xung cho cng sut rt mnh, so vi bin p ngun thng thng th bin pxung cho cng xut gp hng chc ln.

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IV. Diode

1.1 - Cht bn dn l g ?

Cht bn dn l nguyn liu sn xut ra cc loi linh kin bn dn nhDiode, Transistor, IC m ta thy trong cc thit b in t ngynay.Cht bn dn l nhng cht c c im trung gian giacht dn in v cht cch in, v phng din ho hc th bn dn lnhng cht c 4 in t lp ngoi cng ca nguyn t. l cc chtGermanium ( Ge) v Silicium (Si)T cc cht bn dn ban u ( tinh khit) ngi ta phito ra hai loi bn dn l bn dn loi 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 4in t, th tinh khit cc nguyn t Si (Ge) lin kt vi nhau theolin kt cng ho tr nh hnh di.

Cht bn dn tinh khit .1.2 - Cht bn dn loi N

* Khi ta pha mt lng nh cht c ho tr 5 nh Phospho (P) vo chtbn dn Si th mt nguyn t P lin kt vi 4 nguyn t Si theo linkt cng ho tr, nguyn t Phospho ch c 4 in t tham gia lin ktv 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

1.3 - 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 dn 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 mtin t => tr thnh l trng ( mang in dng) v cgi l cht bn dn P.

Cht bn dn P

2 - Diode (i t) Bn dn

2.1 - 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 P - 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 tnsang vng bn dn P lp vo cc l trng => to thnh mt lp Iontrung ho v in => lp Ion ny to thnh min cch in giahai cht bn dn.

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Mi tip xc P - N => Cu to ca Diode .* 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.2.2 - Phn cc thun cho Diode.Khita 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 inp, min cch in thu hp li, khi in p chnh lch gi hai cc t0,6V ( 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. Nutip tc tng in p ngun th dng qua Diode tng nhanh nhng chnhlch in p gia hai cc ca Diode khng tng (vn gi mc 0,6V )

Diode (Si) phn cc thun - Khi Dode dn

in p thun c gim mc 0,6V

ng c tuyn ca in p thun qua Diode

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* Kt lun : Khi Diode (loi Si)c phn cc thun, nu in p phn cc thun < 0,6V th cha cdng i qua Diode, Nu p phn cc thun t = 0,6V th c dng i quaDiode sau dng in qua Diode tng nhanh nhng st p thun vn gi gi tr 0,6V .2.3 - Phn cc ngc cho Diode.Khi phn cc ngc cho Diode tc l cp ngun (+) vo Katt (bndn N), ngun (-) vo Ant (bn dn P), di s tng tc ca in pngc, min cch in cng rng ra v ngn cn dng in i quami tip gip, Diode c th chiu c in p ngc rt lnkhong 1000V th diode mi b nh thng.

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

2.4 - 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 :

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

2.5 - ng dng ca Diode bn dn .

* Do tnh cht dn in mt chiu nn Diodethng c s dng trong cc mch chnh lu ngun xoay chiu thnh mtchiu, cc mch tch sng, mch gim p phn cc cho transistor hotng . trong mch chnh lu Diode c th c tch hp thnh Diode cuc dng .

Diode cu trong mch chnh lu in xoay chiu .3 - Cc loi Diode

3.1 - 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 ccngc, khi phn cc thun Diode zener nh diode thng nhng khi phncc ngc Diode zener s gim li mt mc in p c nh bng gi trghi trn diode.

Hnh dng Diode Zener ( Dz )

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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 diode n p, R1 l tr hn dng.

Ta thy rng khi ngun U1 > Dz th p trn Dz lun lun c nh cho d ngunU1 thay i.

Khi ngun U1 thay i th dng ngc qua Dz thay i, dng ngc qua Dz cgi tr gii hn khong 30mA.

Thng thng ngi ta s dng ngun U1 > 1,5 => 2ln 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.

3.2 - Diode Thu quang. ( Photo Diode )

Diodethu quang hot ng ch phn cc nghch, v diode c mt mingthu tinh nh sng chiu vo mi P - N , dng in ngc qua diodet l thun vi cng nh sng chiu vo diode.

K hiu ca Photo Diode

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Minh ho s hot ng ca Photo Diode

3.3 - Diode Pht quang ( Light Emiting Diode : LED )

Diode pht phang l Diode pht ra nh sng khi c phn cc thun, in plm vic ca LED khong 1,7 => 2,2V dng qua Led khong t 5mA n20mALed c s dng lm n bo ngun, n nhy trang tr, bo trng thi c in .vv

Diode pht quang LED

3.4 - Diode Varicap ( Diode bin dung )

Diode bin dung l Diode c in dung nh t in, v in dung bin i khi ta thayi 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 pngc 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 iuchnh tn s cng hng bng in p.

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3.5 - Diode xung

Trong cc b ngun xung th u ra ca bin p xung , ta phi dng Diodexung chnh lu. diode xung l diode lm vic tn s cao khong vichc KHz , diode nn in thng thng khng th thay th vo v trdiode xung c, nhng ngc li diode xung c th thay th cho v trdiode 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 Diodethng, tuy nhin Diode xung thng c vng dnh du t nt hocnh du bng hai vng

K hiu ca Diode xung3.6 - Diode tch sng.

L loi Diode nh v bng thu tinh v cn gi l diode tip im vmt tip xc gia hai cht bn dn P - N ti mt im trnh indung k sinh, diode tch sng thng dng trong cc mch cao tn dng tch sng tn hiu.3.7 - Diode nn in.

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

Diode nn in 5A

Ngun: hocnghe.com.vnV.Thyristor

1. Cu to v nguyn l hot ng ca Thyristor

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Cu to Thyristor K hiu ca Thyristor S tng tng

Thyristor c cu to gm 4 lp bn dn ghp li tothnh hai Transistor mc ni tip, mt Transistor thun v mt Transistorngc ( nh s tng ng trn ) . Thyristor c 3 cc l Anot, Katotv Gate gi l A-K-G, Thyristor l Diode c iu khin , bnh thng khic phn cc thun, Thyristor cha dn in, khi c mt in p kch vochn G => Thyristor dn cho n khi in p o chiu hoc ct in p ngunThyristor mi ngng dn..Th nghim sau y minh ho s hot ng ca Thyristor

Th nghim minh ho s hot ng ca Thyristor.

Ban u cng tc K2 ng, Thyristor mc d c phn ccthun nhng vn khng c dng in chy qua, n khng sng.

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Khi cng tc K1 ng, in p U1 cp vo chn G lm nQ2 dn => ko theo n Q1 dn => dng in t ngun U2 i qua Thyristorlm n sng.

Tip theo ta thy cng tc K1 ngt nhng n vn sng, vkhi Q1 dn, in p chn B n Q2 tng lm Q2 dn, khi Q2 dn lm p chnB n Q1 gim lm n Q1 dn , nh vy hai n nh thin cho nhau v duytr trang thi dn in.

n sng duy tr cho n khi K2 ngt => Thyristor khngc cp in v ngng trang thi hot ng.

Khi Thyristor ngng dn, ta ng K2 nhng n vn khngsng nh trng hp ban u.

Hnh dng Thyristoro kim tra Thyristor

o kim tra Thyristort ng h thang x1 , tque en vo Anot, que vo Katot ban u kim khng ln , dng Tovit chpchn A vo chn G => thy ng h ln kim , sau b Tovit ra => ng hvn ln kim => nh vy l Thyristor tt .

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ng dng ca Thyristor

Thyristor thng c s dng trong cc mch chnh lunhn i t ng ca ngun xung Ti vi mu .Th d mch chnh lu nhn 2 trong ngun Ti vi mu JVC1490 c s nh sau :

ng dng ca Thyristor trong mch chnh lunhn 2 t ng ca ngun xung Tivi mu JVC

Ngun: hocnghe.com.vnVI. Mosfet

1. Gii thiu v Mosfet

Mosfet l Transistor hiu ng trng( Metal Oxide Semiconductor Field Effect Transistor ) l mt Transistorc bit c cu to v hot ng khc vi Transistor thng thngm ta bit, Mosfet c nguyn tc hot ng da trn hiu ng ttrng to ra dng in, l linh kin c tr khng u vo ln thchhn cho khuych i cc ngun tn hiu yu, Mosfet c s dng nhiutrong cc mch ngun Monitor, ngun my tnh .

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Transistor hiu ng trng Mosfet

2. Cu to v k hiu ca Mosfet.

K hiu v s chn tng nggia Mosfet v Transistor

* Cu to ca Mosfet.

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Cu to ca Mosfet ngc Knh N

G : Gate gi l cc cng S : Source gi l cc ngun D : Drain gi l cc mng Mosfet kn N c hai ming bn dn loi P t trn nn bn dn N, gia hai lp P-

N c cch in bi lp SiO2hai ming bn dn P c ni ra thnh cc D v cc S, nn bn dn Nc ni vi lp mng mng trn sau c du ra thnh cc G.

Mosfet c in tr gia cc G vi cc S v giacc G vi cc D l v cng ln , cn in tr gia cc D v cc S

ph thuc vo in p chnh lch gia cc G v cc S ( UGS ) Khi in p UGS = 0 th in tr RDS rt ln, khi in p UGS > 0 => do hiu

ng t trng lm cho in tr RDS gim, in p UGS cng ln th in trRDS cng nh.

3. Nguyn tc hot ng ca Mosfet

Mch in th nghim.

Mch th nghim s hot ng ca Mosfet

Th nghim : Cp ngun mt chiu UDqua mt bng n D vo hai cc D v S ca Mosfet Q (Phn cc thun cho

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Mosfet ngc) ta thy bng n khng sng ngha l khng c dng ini qua cc DS khi chn G khng c cp in.

Khi cng tc K1 ng, ngun UG cp vo hai cc GS lm in p UGS > 0V =>n Q1 dn => bng n D sng.

Khi cng tc K1 ngt, in p tch trn t C1 (t gm)vn duy tr cho n Q dn => chng t khng c dng in i qua ccGS.

Khi cng tc K2 ng, in p tch trn t C1 gim bng 0 => UGS= 0V => ntt

=> T thc nghim trn ta thy rng : in p tvo chn G khng to ra dng GS nh trong Transistor thng thng min p ny ch to ra t trng => lm cho in tr RDS gim xung .

4. o kim tra Mosfet

Mt Mosfet cn tt : L khi o tr khnggia G vi S v gia G vi D c in tr bng v cng ( kim khng lnc hai chiu o) v khi G c thot in th tr khng gia Dv S phi l v cng.

Cc bc kim tra nh sau :

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o kim tra Mosfet ngc thy cn tt.

Bc 1 : Chun b thang x1K Bc 2 : Np cho G mt in tch ( que en vo G que vo S hoc D ) Bc 3 : Sau khi np cho G mt in tch ta o gia D v S ( que en vo D que

vo S ) => kim s ln. Bc 4 : Chp G vo D hoc G vo S thot in chn G. Bc 5 : Sau khi thot in chn G o li DS nh bc 3 kim khng ln. => Kt qu nh vy l Mosfet tt.

o kim tra Mosfet ngc thy b chp

Bc 1 : ng h thang x 1K o gia G v S hoc gia G v D nu kim ln = 0 l chp o gia D v S m c hai chiu o kim ln = 0 l chp D S

5. ng dung ca Mosfet trong thc t

Mosfet trong ngun xung ca Monitor

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Mosfet c s dng lm n cng xut ngun MonitorTrong b ngun xung caMonitor hoc my vi tnh, ngi ta thng dng cp linh kin l IC todao ng v n Mosfet, dao ng to ra t IC c dng xung vung ca n chn G ca Mosfet, ti thi im xung c in p > 0V =>n Mosfet dn, khi xung dao ng = 0V Mosfet ngt => nh vy daong to ra s iu khin cho Mosfet lin tc ng ngt to thnh dngin bin thin lin tc chy qua cun s cp => sinh ra t trng

bin thin cm ng ln cc cun th cp => cho ta in p ra.* o kim tra Mosfet trong mch .Khi kim tra Mosfet trong mch , ta ch cn thang x1v o gia D v S => Nu 1 chiu kim ln o chiu o kim khng ln=> l Mosfet bnh thng, Nu c hai chiu kim ln = 0 l Mosfet b chp DS.

VII. Transistor1 - Gii thiu v Transistor

1.1 - Cu to ca Transistor. ( Bng bn dn )

Transistor gm ba lp bn dn ghp vi nhau hnh thnh hai mitip gip P-N , nu ghp theo th t PNP ta c Transistor thun , nughp theo th t NPN ta c Transistor ngc. v phng din cu toTransistor tng ng vi hai Diode u ngc chiu nhau .

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Cu to Transistor

Ba lp bn dn c ni ra thnh ba cc , lp gia gi

l cc gc k hiu l B ( Base ), lp 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 hay P )nhng c kch thc v nng tp cht khc nhau nn khng hon v chonhau c.

1.2 - Nguyn tc hot ng ca Transistor.

* Xt hot ng ca Transistor NPN .

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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 ccC 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 C E ( lcny 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 (-) tothnh dng IB

Ngay khi dng IB xut hin => lp tc cng c dng IC chy qua mi CE lmbng 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 mtcng thc .

IC = .IB

Trong IC l dng chy qua mi CE IB l dng chy qua mi BE

l h s khuch 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 mitip gip P-N to thnh dng in, khi xut hin dng IBEdo lp bn dn P ti cc B rt mng v nng pha tp thp, v vy sin 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 nhtrong s cc in t th vo l trng to thnh dng IB cn phn ln s in t b htv pha cc C di tc dng ca in p UCE => to thnh dng ICE chy quaTransistor.* Xt hot ng ca Transistor PNP .S hot ng ca Transistor PNP hon ton tng t Transistor NPN nhng cc tnhca cc ngun in UCE v UBE ngc li . Dng IC i t E sang C cn dng IB i tE sang B.

2 - K hiu v hnh dng ca Transistor

2.1 - K hiu & hnh dng Transistor .

K hiu ca Transistor

Transistor cng xut nh Transistor cng xut ln2.2 - K hiu ( trn thn Transistor )*Hin nay trn th trng c nhiu loi Transistor ca nhiu nc snxut nhng thng dng nht l cc transistor ca Nht bn, M v Trungquc.

Transistor Nht bn : thng k hiu l A, B, C, D V d A564,B733, C828, D1555trong cc Transistor k hiu l A v B l Transistor thun PNP cnk hiu l C v D l Transistor ngc NPN. ccTransistor A v C thng c cng xut nh v tn s lm vic caocn cc Transistor B v D thng c cng xut ln v tn s lm victhp 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 bitloi bng : Ch A v B l bng thun , ch C v D l bng ngc, chth hai cho bit c im : X v P l bng m tn, A v G l bng caotn. Cc ch s sau ch th t sn phm. Th d : 3CP25 ,3AP20 vv..

2.3 - Cch xc nh chn E, B, C ca Transistor.

Vi cc loi Transistor cng xut nh th th t chn C v B tu theo bng canc no s xut , nhng chn E lun bn tri nu ta Transistor nh hnhdi

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 chnh xc ta dng phng php obng 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.

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Transistor cng xut ln thngc th t chn nh trn.

* 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 = nhauth chn c que t c nh l chn B, nu que ng h c nh l queen th l Transistor ngc, l que th l Transistor thun..

3- Phng php kim tra TransistorTransistorkhi hot ng c th h hng do nhiu nguyn nhn, nh hng do nhit

, m, do in p ngun tng cao hoc do cht lng ca bn thnTransistor, kim tra Transistor bn hy nh cu to ca chng.

Cu to ca Transistor

Kim tra Transistor ngc NPN tng t kim trahai Diode u chung cc Ant, im chung l cc B, nu o t B sang C

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v B sang E ( que en vo B ) th tng ng nh o hai diode thunchiu => kim ln , tt c cc trng hp o khc kim khng ln.

Kim tra Transistor thun PNP tng t kim trahai Diode u chung cc Katt, im chung l cc B ca Transistor, nuo t B sang C v B sang E ( que vo B ) th tng ng nh o haidiode thun chiu => kim ln , tt c cc trng hp o khc kimkhng 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 => kimkhng ln l transistor t BE hoc t BC* 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 vok hiu ta bit c Transistor trn l bng ngc, v ccchn ca Transistor ln lt l ECB ( da vo tn Transistor ). < xem li phn

xc nh chn Transistor >

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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.

-

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

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Php o cho bit bng b t BE

Bc 1 : Chun b . Bc 2 v 3 : o c hai chiu gia B v E kim khng ln. => Bng t BE

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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.

3- Phng php kim tra Transistor

Transistor khi hot ng c th h hng do nhiu nguyn nhn, nh hng do nhit, m, do in p ngun tng cao hoc do cht lng ca bn thnTransistor, kim tra Transistor bn hy nh cu to ca chng.

Cu to ca Transistor

Kim tra Transistor ngc NPN tng t kim trahai Diode u chung cc Ant, im chung l cc B, nu o t B sang Cv B sang E ( que en vo B ) th tng ng nh o hai diode thunchiu => kim ln , tt c cc trng hp o khc kim khng ln.

Kim tra Transistor thun PNP tng t kim trahai Diode u chung cc Katt, im chung l cc B ca Transistor, nuo t B sang C v B sang E ( que vo B ) th tng ng nh o haidiode thun chiu => kim ln , tt c cc trng hp o khc kimkhng 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 => kimkhng ln l transistor t BE hoc t BC* o t B sang E hoc t B sang C kim ln c hai chiu l chp hay d BE hoc

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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 vok hiu ta bit c Transistor trn l bng ngc, v ccchn ca Transistor ln lt l ECB ( da vo tn Transistor ). < xem li phn xcnh chn 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

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Php o cho bit bng b t BE

Bc 1 : Chun b . Bc 2 v 3 : o c hai chiu gia B v E kim khng ln. => Bng t BE

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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.

VIII. IC n p :

IC n p hLA78..

IC n p LA7805

LA7805 IC n p 5V LA7808 IC n p 8V LA7809 IC n p 9V LA7812 IC n p 12V

Lu :H IC78.. ch cho dng tiu th khong 1A tr xung, khi rp IC trongmch th U in > Uout t 3 n 5V khi IC mi pht huy tcdng.

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3.3 ng dng ca IC n p h 78..

IC n p h 78.. c dng rng ri trong cc bngun , nh B ngun ca u VCD, trong Ti vi mu, trong my tnh vv

ng dng ca IC n p LA7805 vLA7808 trong b ngun u VCD

4 Mch n p tuyn tnh (c hi tip)

4.1 S khi ca mch n p c hi tip .

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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 haitrng 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.

Cho in p mt chiu u ra c cht lng cao, gim thiu c hin tng gnxoay 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 iu 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 hngngc 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 nuin p ra gim => thng qua mch hi tip iu chnh => n cngxut li dn tng => v in p ra tng ln =>>kt qu in p u ra khng thay i.

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Mch chnh lu

Mch chnh lu in xoay chiu

1.1 B ngun trong cc mch in t .

Trong cc mch in t ca cc thit b nhRadio -Cassette, mlpy, Ti vi mu, u VCD v v chng s dngngun mt chiu DC cc mc in p khc nhau, nhng ngoi zc cmca cc thit b ny li cm trc tip vo ngun in AC 220V 50Hz ,nh vy cc thit b in t cn c mt b phn chuyn i t ngunxoay chiu ra in p mt chiu , cung cp cho cc mch trn, b phnchuyn 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. Mch lc 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.

1.2 Mch chnh lu bn chu k .

Mch chnh lu bn chu k s dngmt Diode mc ni tip vi ti tiu th, chu k dng =>Diode c phn cc thun do c dng in i qua diode v i quati, chu k m , Diode b phn cc ngc do khng c dng qua ti.

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

1.3 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 dym

chu k m, in p trn cun th cp o chiu ( udy trn m, di dng) dng 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.

2 Mch lc v mch chnh lu bi p

2.1 Mch lc dng t in.

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Sau khi chnh lu ta thu c in p mt chiu nhpnh, nu khng c t lc th in p nhp nh ny cha th dng cvo cc mch in t , do trong cc mch ngun, ta phi lp thm cct lc c tr s t vi trm F n vi ngn F vo sau cu Diodechnh lu.

Dng in p DC ca mch chnh lutrong hai trng hp c t v khng c t

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

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 C1trong cc b ngun thng c tr s khong vi ngn F .

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

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Trong cc mch chnh lu, nu c t lc m khng c tihoc ti tiu th mt cng xut khng ng k so vi cng xut ca binp th in p DC thu c l DC = 1,4.AC

2.2 Mch chnh lu nhn 2 .

S mch ngun chnh lu nhn 2

tr thnh mch chnh lu nhn 2 ta phi dnghai t ho cng tr s mc ni tip, sau u 1 u ca in p xoauchiu vo im gia hai t => ta s thu c in p tng gp2 ln.

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 in p ra tng gp 2 ln.

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B. THC HNH1.Cch s dng ng h VOM o v kim tra cc linh kin:

ng h vn nng c

p AC v o dng iu im ca n h

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S dng

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nhm th=> s hng

* Nu thang

kim ng h khhng . (i khi

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nhmng h

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Tuyt i khngin hoc thangkhi ta o in

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Php

o dng

Cch 1:Dng tha

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Cch 2 :

Cch c tr

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*Nu ta thangcao nht l 250

* c gi t

Php o

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Php o

Ph

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Php

Php o

+ t ng h t

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Php

+ o thun chi

=>kim ln, => Diode cn

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2. Thc hnh o kim tra chn ca Transistor

C 1061 :t transistor nm hng mt ch ln trn, que en t bn tri, ln lt o que

vo hai chn cn li, kim ln => y l transistor loi N, cc B l chn bn tay tri( que en ), hai chn cn li l C v E. C1815:

t trasistor p mt ch xung di, que en t bn tay tri, que ln lt t vohai chn cn li, o thy kim ln l loi NPN => chn B que en, 2 chn cn li lC v E, chn C nm gia. MJ 2955:t trasistor hng chn ln trn, que t vo chn bn phi, que en ln lt tvo hai chn cn li, o kim ln => transistor loi P, cc B ti que , hai cc cn lil C v E. C535C:t transistor p mt ch xung di, que en t vo chn bn tri, que t vohai chn cn li, o kim ln => transistor loi N cc B l chn bn tay tri que en,hai cc cn li l C v Em C nm gia.

Xc nh loi transistor:Kp que o ni cc dng ca pin ( que en ) c nh vo chn B, sau dngque cn li ca ng h chm ln hai chn cn li ca transistor

Nu trong c hai ln o kim ng h u ln chnh l NPN Nu trong c hai ln o kim ng h khng ln thtransistor l NPN Xc nh chn E v C:

Bt chuyn mch VOM v thang o Rx10k xc nh chn E v C i vi transistor loi NPN kp que caVOM vo hai chn C v E xc nh trn, sau dng ngn tay t trmvo gia chn v chn ang ni vi cc dng ca ng h, nu kim ng hkhng ln hoc ln rt t tc l ang o sai, o hai que o, gi nguyn dy niB vi mt chn bt k, tin hnh o li,

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+ nu kim ng h ln th chn ang ni vi cc dng ca pin ng h l chn C,chn cn li l chn E

i vi loi PNPDy ni B vi mt cc c nh ch o que o, ni cc B vi que , hai chncn li nu o kim ln th chn ang ni vi cc m ca pin ng h l chn C, cnli l chn E.

3. Thc hnh Hn

Hn hnh cu:

Hn theo b mt:

Hn ch thp:

Thc hnh lp mch trn test board

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Thc hnh v Orcard trn my ..

o Mach ngun:

S nguyn l:

Mch in:

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o Mch hin th Led 7 on

S nguyn l:

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Mch khuch i tn hiu dung transistor :S nguyn l:

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102


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Thc hnh lm mch thc t:

1.Mch Dao ng a Hi:

S nguyn l v mch in v tay:

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2. Mch Ngun chnh lu ton k dung IC 7905

S nguyn l v mch in :

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3. Mch Dimmer

S nguyn l v mch in :

Nhn xt ca ging vin hng dn

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