NGUYN THANH TR - THI VNH HIN

250 BI TPKV THUT IN T

NH XUT BN GIO DC VIT NAM

Chng 1

IT

1.1. TM TT PHN L THUYT

Hiu ng chnh lu ca it bn dn l tnh dn in khng i xng. Khi it c phn cc thun, in tr tip gip thng rt b. Khi it c phn cc ngc in tr tip gip thcmg rt ln. Khi in p ngc t vo ln it b nh thng v mt i tnh chnh lu ca n. Trn thc t tn ti hai phofng thc nh thng i vi it bn dn. Phcng thc th nht gi l nh thng tm thi (zener). Phng thc th hai gi l nh thng v nhit hay nh thng thc l. Ngi ta s dng phng thc nh thng tm thi lm it n p.

Phng trnh c bn xc nh dng in Id chy qua it c vit nh sau:

~ DS enu.. ( 1- 1)

y: - = , l th nhit;q

- k = 1,38.10"^ , hng s Boltzman;K

- q = 1,6.10 'c , in tch ca electron;- n = 1 i vi Ge v n = 2 i vi Si;- T nhit mi trng tnh theo K.

T phng trnh (1-1) ngi ta xy dng c c tuyn Volt-Ampe = f(Uj3) cho it v dng n inh ton cc thng s c lin quan i vi

cc mch in dng it.hg dng quan trng ca it l:

a) Chnh lu dng in xoay chiu thnh mt chiu nh cc s c bn s dng cc loi it khc nhau (it c iu khin v it khng iu khin).

b) Hn ch bin in p mt gi tr ngng cho trc.c) n nh gi tr in p mt chiu mt ngng xc lp Uz nh nh

thng tm thi (zener).M hnh gn ng m t it trong cc mch in c xem nh:

a) L mt ngun in p l tng c ni tr bng khng khi it chuyn t trng thi kho sang m ti mc in p U K = Up.

b) L mt ngun dng l tng c ni tr rt ln khi it chuyn t trng thi m sang kho ti mc in p = oV

c) ch xoay chiu khi tn s tn hiu cn thp, it s tcmg ng nh mt in tr xoay chiu c xc nh theo biu thc (1-2) di y :

( 1-2 )

Cn khi' tn s tn hiu cao, cn ch ti gi tr in dung k sinh ca it Cd, n c mc song song vi in tr xoay chiu r .

1.2. BJ TP C LI GII

Bi tp 1-1. Xc nh gi tr th nhit (U-r) ca it bn dn trong iu kin nhit mi trng 20c.

Bi gii

T biu thc c bn dng xc nh th nhit

u ,= i q

Trong :

- k = 1,38.10'^ , hng s Boltzman;K

- q = 1 , 6 . in tch ca electron;- T nhit mi trng tnh theo K.Tiay cc i lng tcng ng vo biu thc ta c:

U, = = ^ M . 2 5 . 2 7 , n V q 1,6.10"'

Bi tp 1-2. Xc nh in tr mt chiu Rj3 ca it chnh lu vi c tuyn V-A cho trn hnh 1-1 ti cc gi tr dng in v in p sau:

= 2mA

Uo = -10V.

Bi gii

a) Trn c tuyn V-A ca it cho ti I = 2mA ta c:

Ud = 0,5V nn:

K = =u.. 0,5Id 2.10 -3

= 250Q

b) Tng t ti Uq = -lOV

Ta c Id = l|iA nn;10

RHinh 1-1

= 10MQ.

tp 1-3. Xc nh in tr xoay chiu ca it chnh lu vi c tuyn V-A cho trn hnh 1-2.

a) Vi Id = 2mA

b) Vi Id = 25mA.

Bi gii

a) Vi Ij) = 2mA, k tip tuyn ti im ct vi c tuyn V-A trn hnh 1-2 'a s c cc gi tr Ij3 v Up tng ng xc nh AU v AIp nh sau:

= 4niA; U = 0,76V In(mA)

Ip = OrnA; p = 0,65V

AIp = 4m A - OmA = 4m A

AU d = 0 ,7 6 V -0 ,6 5 V = 0 ,11V

Vy:

" AI 4.10-

302520

10

AI.

AI, u (v; ---0 0,2 0,4 0,60,7 0,8 1,0

Hinh 1-2

b) Vi Id = 25mA. Cc bc tng t nh cu a) ta xc nh c cc i lng tng ng di y:

Id = 30mA; D = 0,8VId = 20mA; Ud = 0,78VAIjj = 30 - 20 = lOmAAd = 0,8 - 0,78 = 0,02V

V y , = ^ = = 2 . AI 10.10''

04 ) Bi tp 1-4. Cho c tuyn V-A ca mt it nh trn hnh 1-2. Xc nh in tr mt chiu ti hai gi tr dng in.a) Ij5 = 2mA.b) Iq = 25mA v so snh chng vi gi tr in tr xoay chiu trong bi tp 1-3.

Bi gii

T c tuyn V-A trn hnh 1-2 ta c cc gi tr toig ng sau;

a) Id = 2mA; D = 0,7V

Nn: R . = ^ = - ^ = 3 5 0 QAL 2.10

so vi = 27,5Q.

b) Id = 25mA; D = 0,79V

Nn: R , = ^ = - ^ ^ = 3 1 , 6 2 Q'* AL 25.10"'

so vi = 2 Q.

Bi tp 1-5. Cho mch in dng i nh hnh l-3a v c tuyn V-A ca it nh trn hnh l-3b.

a) Xc nh to im cng tc tnh Q[)o; liX)]-b) Xc nh gi in p trn ti Ur.

Bi gii

a) Theo nh lut Kirchoff v in p vng ta c:

8

uD

R.

IkQ

u.

a)Hnh 1-3

E - u - u, = 0 hay E = Uo + ,y chnh l phcrtig trnh na ti mi chiu cci mch din dng i trn.Dng ng ti mt chiu thng qua hai im cl trn trc lung vi

U|) = o v v trn trc honh vi Ip = 0.Ti p = 0 ta c E = 0 + IpR,

Nn: D=-E lOV

R 10'o= 10mA

Ti I|J = 0 la c l = U|J + (OA).R,

Up = E| -lO Vi) UdoI vi to tcmg ng:

I[)0 = 9,25m A

Upo = 0 ,78V

b) in p ri trn ti R, s l:

u =I.R, =I,.R, =9,25.10-M0 =9,25V

Hoc Ur, c th c tnh:

Ur, = E -U do= 10-0,78 = 9,22V

S khc nhau trong hai kt qu trn do sai s khi xc nh theo thi biu din c tuyn V-A i vi it trn hnh 1-3 v hnh 1 -4.

Bi tp 1-6. Tnh ton lp li nh bi tp 1-5 vi R, = 2kQ.

Bi gii

a) T biu thc: E lOV

R 2kQ= 5mA

U^ = E = 10V

ng ti mt chiu (R_) c dimg nh trn hnh 1-5 v ta c to im Q[Ido; UdoI tcmg ng:

Ido = 4,6mA

Udo = 0,7Vb) in p ri trn ti R, s l:

=1 .R, =IdoJR, =4,6.10-' .2.10' =9,2V hoc

= E -U do=10V-0,7V=9,3V

7 ] Bi tp 1-7. Tnh ton lp li cho bi tp 1-5 bng cch tuyn tnh ho c tuyn Volt-Ampe cho trn hnh l-3b v it loi Si.

Bi gii

Vi vic tuyn tnh ho c tuyn V-A ca it trn ta v li c tuyn nh trn hnh 1-6.

10

Dng ng ti mt chiu (R_) cho mch tng t nh trong cu a) ca bi tp 1-5 v c biu din trn hnh 1-6.ng ti mt chiu c tuyn V-A ti Q vi to tong ng.

Ido = 9,25mAU do = 0,7V. Hnh 1-6

( 8 j Bi tp 1-8. Tnh ton lp li cho bi tp 1-6 bng cch tuyn tnh ho c tuyn V-A cho trn hnh l-3b v it loi Si.

Bi gii

Vi vic tuyn tnh ho c tuyn V-A ca it trn ta v li c tuyn nh trn hnh 1-7.

Dng ng ti mt chiu (R_) cho mch tng t nh trong cu a) ca bi tp 1-6 v c biu din trn hnh 1-7.

ng ti mt chiu (R_) ct c tuyn V-A ti Q. Vi to tng ng:

Ido ~ 4,6rnA = 0,7V.

Bi tp 1-9. Tnh ton lp li cho bi tp 1-5 bng cch l tng ho c tuyn V-A cho trn hnh l-3b v it loi Si.

Bi gii

Vi vic l tcmg ho c tuyn V-A ca it, ta c nhnh thun ca c tuyn trng vi trc tung (Ip), cn nhnh ngc trng vi trc honh (Ud) nh trn hnh 1-8.

Hnh 1-7

11

Dng dng li mt chicu (R_) cho mch tng t nh Irong cu a) ca bi lp 1-5.

ng ti mt chiu ct c tuyn V-A ti im Q vi to tcyng ng:

no = iOmAU,K, = OV.

ng ti mt chiu (R_) c biu din nh trn hnh 1-8.

Bi tp 1-10. Cho mch in dng it loi Si nh hnh i -9.

Xc nh cc gi tr in p v dng in Uq. U|(, I|y

Bi gii

Bit rng it loi Si lm vic bnh thng ngng thng nm trong khong l 0.5V -r 1,25V. Chn ngng m viq cho it:

U = 0,7V; E = 8V.

in p ri trn in ir ti R s l:

U, = E- Up = 8 -0 ,7 = 7,3V Hnh 1-9Dng in chy qua it I|) = 1,;, (dng

qua ti R) s :

Id = Iu = - ' = ^ = - ^ ^ = 3.32mA " ' R 2 ,2 .10 '

Bi tp 1-11. Cho mch in dng it nh hnh 1-10. Xc nh inp ra trn ti v dng in Id qua cc it D, Dj.

Bi gii

Chn ngng in p thng cho hai it D| v D, lng ng.

=0,7V di viitSi

12

=0,3V i vi it Ge.

in p ra trn ti s l:

= 12-0,7-0,3= liv.Dng in qua cc it D|,

Ip Dj Si D, Ge

E

.L +

12V u5,6kQ

ra

v E s l:

r r 11Hnh 1-10

R 5,6.10l,96m A.

(^1^ Bi tp 1-12. Cho mch in dng it nh hnh 1-11 Xc inh cc in p v dng in u, Up , Ij3.

Bi gii

D,Si D.Si 1 ki12V

R-5,6kQ

Hnh 1-11

Id Uo,=OV I=I,,=I,=0A=I,

u.rn 12V D. D2

r :5,6kf

T uR ra

Hnh 1-12

Do D| c phn cc thun, cn Dt c phn cc nghch, ta v li s tng ng ca mch vi gi thit c hai it u l tcmg nh trn hnh 1-12.

Khi ; u = Id.R = Ir.R = OA.R = o vV it D, trng thi h mch nn in p ri trn n chnh l in p

ngun E:

U ,= E -I2V

Nu theo nh lut Kirchoff ta cng s c kt qu nh trn.

E -U D, =0

u = E -U ,-U ^ = I2 -0 -0 = 1 2 V .D-, D, ra

13

+ u , - DSi

E,=10VR 4,7kQ

(^1^ Bi tp 1-13. Cho mch in dng it nh hnh 1-13

Xc nh cc dng in v in p I, U|, 2,

u

, . 0 ^ 1VW^->

+ L

R, 2,2kQ E ,^IO V

R, I

E3=-5V

I +

R, u .

E , : 5V

Hnh 1-14Hnh 1-13

Qin in p ing cho it D loi Si 0,7V ta v li s trn nh hnh 1-14. Dng in I c tnh:

, ^ E . E - U (1 0 .5 -0 ^ )R,+R2 (4,7+2,2)10^

in p U|, 2 tng ng trn R|, R, s l:

u , =IR, =2,07.10'\4,7.10^ =9,73V

2 =IR2 =2,07.1012,2.10^ =4,55V

in p ra s l:

u = 2 - E, = 4,55 - 5 = -0,45V Du tr (-) trong kt qu biu th rng cc tnh ca in p ra (U) s c

Bi gii

Chn gi tr in p thng cho cc it D , loi Si 0,7V. S 1-15 c v li nh hnh 1-16.

Dng in I c tnh

RI = H ^ = ^ = i ^ = 2 8 , 1 8 m A

R 0 ,3 3 .1 0 '

14

ra

Hnh 1-15 Hnh 1-16

Nu chn D v D, ging nhau ta c dng qua chng s nh nhau v tnh c;

I =I Q gD, D, ^

in p ra chnh l in p thng ri trn it D| v D,

U = 0 ,7V

Bi tp 1-15. Cho mch in dng it nh hnh 1-17. Xc nh dngin I chy qua mch.

Bi giai

Di tc ng ca hai ngun in p E| v E. D| c phn cc thun, cn D c phn cc nghch, ta v i s tng ong nh hnh 1-18 di y:

Si

I R

E|=20V 2,2kQ

Si

N 1D.D,

------ ------- i E,=4V +----- A

R 2.2knE, -4 :^ 0 V

- E2=4V

Hnh 1-17

Dng in I c tnh:Hnh 1-18

R 2,2.10'

15

E t l2V

Bi tp 1-16. Cho mch in dng it nh hnh 1-19. Xc nh inp ra trn ti R.

R

4rO,3V

u.2,2kQ

ra

Hnh 1-20

Bi gii

V D| v D, khc loi (D, - Si; D-, - Ge) nn khi c cp in p phn cc E it D-, (Ge) lun lun thng ngng 0,3V, cn it D| s lun lun kho do ngng thng ti thiu ca it loi Si l 0,7V.

S tong ofng ca mch c v li nh trn hnh 1 -20.

in p ra (U) trn ti R c tnh:U,, = E - u = 12-0 , 3= 11,7V.

17 ) Bi tp 1-17. Cho mch in dng it,nh trn hnh 1-21. Xc nh dng in I I,, .Bi gii

Chn ngng in p thng cho hai it D 2 loi Si bng 0,7V.

Dng in I| c tnh:u . 0,7

SiH >h

D.

R| 3,3kQ- aXat- i

I

E - i20V

I,= D,R. 3,3.10

3-=0,212mA

d , Si

h4-AAAr

Theo nh lut Kirchoff v in p vng ta c:

5,6kf

Hnh 1-21

- U ,+ E - U - U ,= 0

16

Hay

Do :

Ur =E -U c -U =20-0,7-0,7= 18,6V

, _ u 18,6I= -^ = 3 ,3 2 m A

R, 5,6.10^

Theo nh lut Kirchoff v dng in nt ta c;

=1^- I ,=3,32-0,212 = 3,108mA

Bi tp 1-18. Cho mch in dng it nh hnh 1-22 (cng lgic OR dng). Xc nh in p v dng in ra trn ti I, u.

Bi gii

V D , Dj u l it loi Si, nu chn ngng thng cho chng bng 0,7V th D s lun lun thng cn Dj lun lun b kho. Mch in c v li nh hnh 1-23.

(1) * - i E.=10V

Si DI

(0)E, ov

D,SiSD,

ura

+E *:r iov

1

t I '-0.7V - *-

urara

R ^ ik n

Hnh 1-22

in p ra s l:

Hnh 1-23

U = E -U d,= 10-0 ,7= 9 ,3V

I =i2-=_iL=9 3mA. R 1.10^

Bi tp 1-19. Cho mch in dng it nh hnh 1-24 (cng lgic AND dng). Xc nh dng in ra (I) v in p ra (U^) n ti R.

Bi gii * Chn ngng thng bng 0,7V cho D| v D2, khi s 1-24 c v

li nh hnh 1-25, tng ng vi thng, cn D, tt.

2- 250BTKTINT.A 17

E - i r l O V

0 , 7 V u

u IraD2R ^ Ikn

"^ElOV

Hnh 1-25

in p ra chnh l in p thng cho it D2 v bng Up . Vy ta c:

=0,7V.

Dng in qua ti R cng chnh l dng qua D2 v c tnh:E -U ,

= l l ^ = 9 , 3 m A . R 1.10'

Bi tp 1-20. Cho mch chnh lu dng it nh hnh 1-26.V dng in p ra n ti R v xc nh gi in p ra mt chiu

sau chnh lu Ujc vi it D l tng.

uV 2

D

R 2kQ

Hnh 1-26

Bi gii

b)

Vi mch in cho trn hnh 1-26 it D s dn in (thng) trong na chu k dng (+) ca tn hiu vo (t 4-T/2) cn trong na chu k m (-) ca tn hiu vo (t T/2^T) it D s b kho hon ton. Dng ca in p ra trn ti c biu din nh trn hnh l-27b, cn s tng ofng c biu din nh hnh l-27a.

18 2- 250BTKTINT - B

+

u

+

R S 2kQUde

a) Hinh 1-27 b)

Dien p ra mt chiu tren tai didc tnh:

Ud, = 0,318U, = 0,318.20V = 6,36V

1-21. Cho mach chinh lim dng di't nhuf trn hinh 1-28.

Ve dang din p ra trn tai R va tnh gi tri din p ra mt chiu trn ti R vi di't D thirc t' loai Si

Uv

D

R 2kQ

a) Hinh 1-28

Bi gii

Vi di't D thuc (khdng 1; tucmg) ni trf ca di't khi phn cuc veri tiimg nfa chu ky ca tn hiu vo s c gi trj xc lp. Khi di't thng ni trd ca D rt b con khi D kho s tuofng ng rt ln. Vi vy dang din p ra diroc biu din nhir trn hinh 1 -29.

Din p ra mt chiu trn ti R duoc tnh: = -0,318(U, - U )

= -0,318(20-0,7) = -6,14V

Hinh 1-29

19

Nh vy so vi trng hp D l tcmg trong bi 1-20 in p ra gim0,22V tng ofng 3,5%.

( 2^ Bi tp 1-22. Tnh ton lp li bi 1-20 v 1-21 vi gi tr = 200Vv rt ra kt lun g?

Bi gii

i vi it D l tng ta c:u.,, = 0,318U^ = 0,318.200V = 63,6V

i vi it D thc (khng l tng) ta c:

U,, = 0,318(U,-Uo)= 0,318 (200-0,7) = 63,38V

Kt lun: Khi in p vo c mc ln = 200V).

i vi trng hp it thc, in p ra mt chiu gim 0,22V tng ng 0,3459% t hn 10 ln so vi kt qu trong bi 1-21 khi c mcb ( u l = 20V ).

( 2^ Bi 1-23. Cho mch chnh lu hai na chu k dig it nh trn hnh 1-30

a) V dng sng sau chnh lu trn ti R,.

b) Tnh gi tr in p ra mt chiu trn ti Uj,,.

c) Tnh gi tr in p ngc t ln D v Dj.

Bi gii

a) y l mch chnh lu hai na chu k dng it. d dng nhn bit trng thi lm vic ca mch ta v li s tng ng khi cc it

20

thng, kho vi tng 1/2 chu k ca tn hiu vo. V d: vi 1/2 chu k dng ca tn hiu vo (t O- T/2) s tng ng c biu din trn hnh 1-31.

+

a) b)

++

R. .> > *''

Bi gi

t ,(V)

a) Hnh 1-32 b)

5V

U R U

Gi thit it D l tng, d dng nhn thy D lun lun thng vi 1/2 chu k dng (+) ca in p vo. Mch in tng ng lc ny c v nh trn hnh 1-33.

in p ra s l: = Uy + 5V vit D s thng cho n thi im Uy gim xung n -5V na chu k m. Sau khong thi gian it D s trng thi phn cc ngc, dng qua it v qua ti R lun bng khng, nn in p ra cng s bng khng (tng ng vi mc in p vo U y < -5V. Khi U y > -5V cng tcnigng trong khong na chu k m ca tn hiu vo, tc khi U v > -5V it D thng tr li v qu trnh s lp li nh phn tch trn. .

Dng in p ra c biu din nh trn hnh 1-34:

Hinh 1-33

' UJV)

25^=20V +5V =25V

5 / / 71-------- J-5

2

Hnh 1-34 b)

^2^ Bi tp 1-25. Cho mch in dng it nh hnh 1-35. V dng in p ra trn ti R.

22

20

-10

Uv(V) H ^U=5V

u.u

+

R u

t(s)

ra

a) Hinh 1-35

Bi gii

b)

Gi thit it D l tng.' Trong khong thi gian t O--T/2 vi Uv = 20V it D thng hon ton, s in tng ng c v li nh trn hnh 1 -36 v in p ra s l:

U,=25V =OV

Hnh 1-36

= Uv + u = 20 + 5 = 25V

Trong khong thi gian t T/2 T T vi Uy = -lOV it D lun lun trng thi kho, s in tcfng cmg c v li nh trn hnh 1-37 v in p ra trn ti R lc s l:

Hnh 1-37

U , = Ir.R = O.R = ov

Dng in p ra trn ti R c biu din nh trn hnh 1-38.

Bi tp 1-26. Cho mch in dng it nh hnh 1-39 (mch hn bin song song).

V dng in p ra trn ti R,.

'U(V)

25

T0

r t(s)

2

Hnh 1-38

23

Bi gii

Vi gi thit it D l tng, n s thng khi in p vo Uy ^ 4V, ngha l ton b 1/2 chu k m (-) ca in p vo v mt phn ca 1/2 chu k {+) dng ca in p vo vi Uv < 4V. S in tng ng c v li nh trn hnh 1-40 v ong khong thi gian in p ra lun lun bng ngun u = = 4V.

RvwR ' +

J-. t4V+

Hnh 1-40

Trong khong thi gian khi Uy > 4V, it lun lun trng thi kho nn in p ra trn ti s ln hn 4V v bng in p vo. S in tng ng c v li nh hnh 1-41.

Dng in p ra c biu din nh n hnh 1-42 di y.

( 27^ Bi tp 1-27. Cho mch in dng it nh hnh 1-43. V dng in p ra khi dng it D loi silic vi Ud = 0,7V.

vura

4V

Hnh 1-41

Hnh 1-42

24

RAAr

D i : SiU.

U--4VUra

RAA/V-

b)

Bi gii

Vi it thc, ngng thng cho trong u bi Uo = 0,7V mch in c v li nh hnh 1 -44.

TTieo nh lut Kirchoff v in p vng ta c:

U v + U d - U = 0

hay Uv = U - U o = 4 - 0 ,7 = 3 ,3V

Vi Uv > 3,3V it D lun lun trng thi kho nn in p ra s ng bng in p vo (U v).

.U 'o ,7 V

T u -iAv

Hnh 1-44

Hnh 1-45

Vi in p vo Uv < 3 ,3V it trng thi thng hon ton nn in p ra s !:

U,, = 4 - 0 ,7 = 3 ,3V

Dng in p ra c biu din nh hnh 1-45.

/2^) tp 1-28. Cho mch in dng it zener nh hnh 1-46 v c

tuyn V-A ca zener nh trn hnh 1-47.

a) Xc nh cc gi tr in p Ur, u dng in Iz qua zener v cng sut tiu tn trn zener Pz-

b) Lp li tnh ton trong cu a, khi thay R, = 3kQ

25

RAA/V-Ikn

^=16V U^=10V2

Pz,a.=30mA

l,2kQ '

Hnh 1-46

Bi gii

a) thun tin cho vic tnh ton cc thng s ca mch ta v li s tong ng nh hnh 1-48.

T hnh 1-48 ta c:

u

R L

IkQ 1^16V u"" l,2kQ '

U = U, = ^' R+R,

RHnh 1-48

16V.1,2.10- = 8,73V1.10 + 1,2.10

in p = u, t ln zener bng 8,73V lun lun nh hn y = lOV nn zener lun lun trng thi kho v I7 = OA.

in p st trn R s l:

Ur = Uv - u, = 16 - 8,73 = 7,27V Cng sut tiu tn trn zener l:

p = U2.Iz = U z .0 = 0W

b) Vi R, = 3kQ.in p u trn s hnh 1-48 s l:

U = - H ^ . R , = 4 5 ^ = , 2 VR + R, 1.10+3.10

26

V in p t ln zener u = 12V > 2 = lOV nn zener s c m thng. S mch in c v li nh hnh 1-49.

in p trn ti R, chnhbng in p \Jj v bng lOV I-------------- --------------* ------------------- 1 += U. = U,.

16-10 = 6V

I, = = = 3,33mA ' R. 3kQ Hnh 1-49

I,u 6V

6mA

U^=50V

V R IkQ

. I, = 6 - 3,33 = 2,67mA

= Uz.Iz = 10V.2,67mA = 26,7mW

Thp hn tr cc i cho php = 30mW.

Bi tp 1-29. Cho mch n p dng zener nh hnh 1-50.

a) Xc nh khong gitr in tr ti R, v dng in qua ti R, sao cho in p ra trn n lun lun n nh U = 2 = 10V = U,. Hnh 1-50

b) Xc nh cng sut tiu tn cc i trn zener.

Bi gii

a) Ta bit rng zener bt u thng khi in p ngc t ln n u >U2- (hnh 1-47 hay 1-48). Khi in tr ti cc tiu R, i c xc nh;

- Iz.ax=32mA

R = - ^u.,-u. 50-10250Q

Ch : Khi dng qua zener cc tiu (l thuyt th = 0), dng qua ti tng ng c gi tr cc i Vi in p n nh trn ti u, = U2 th

27

trong trng hp gi tr R, c xc nh chnh l R,j in p ra trn ti khng i u, = = const.

in p ri trn in tr hn ch R s l:

U r = U v - U z = 50- 10 = 40V

I _ U r _ 4 0 V _ ^V L = ^ = - ^ = 4 0 m A" R IkO

Dng in cc tiu trn ti s l:

U = lR-I,n,ax = 4 0 -3 2 = 8mAin tr ti cc i s l:

Ru 10T=1250f=l,25kD I.min 8-10( iY)in

th biu din vng n p ca mch v trn hnh 1-51.

f U,(V) t U,(V)

250n l,25kn R, 0

a) Hinh 1-51

b) Cng sut tiu tn cc i trn zener s l; Pzmax = u , . = lOV . 32mA = 320mW

b)

z * *Zmax.030 ) Bi tp 1-30. Cho mch in dng it n p (zener) nh trn hnh 1-52.Xc nh khong bin i ca in p vo in p ra trn ti lun

lun n nh v bng lOV = Uz-

Bi gii

Ta bit rng vi R, = const (c nh) in p thng cho zener bt u t > Uz t ln zener.

T s ta c;' R + R. '

28

U,R, + U ,.R = UvR,

NnR.

R Vmin

Thay cc gi tr Uz, R, R, ta xc nh c c Uvmin l:

__ j^a a . . _ r L

220

U y=? J,=20V ^ R.

Hlnh 1-78

38

Chong 2

TRANSISTOR LNG cc V TRANSISTOR TRNG

2.1. TM TT PHN L THUYT

Transistor lftig cc (BJT) gm ba lp bn dn p v N ghp xen k nhau; tu thuc vo cc tip gip P-N m hnh thnh hai loi transistor: P-N-P (transistor thun) v N-P-N (transistor ngc) nh k hiu trong hnh 2-1.

+ cI

B

c.

B -

t

T ransistor riguc T ransistor thuna) N-P-N b) P-N-P

Hnh 2-1. K hiu hai loi transistor N-P-N v P-N-P

Chiu ca dng in mt chiu chy qua transistor c ch trong hnhv trng vi chiu mi tn quy c cc emit.

lm vic ch khuch i, in p ngun E c cp cho cc E-c tu thuc vo loi transistor c ch trong hnh 2-1. in p phn cc cho tip gip B-E phi lun l phn cc thun, tc l i vi transistor N-P-N cc haza phi dng so vi cc emit, ngc li, i vi transistor thun P-N-P cc B phi m hn so vi cc E.

Trong c hai loi transistor, cc dng in u c th coi nh tp trung ti mt nt

Ie + Ic + Ib = 0 hay Ie = Ic + Ib v Ig Ig, ic

39

C ba cch mc s c bn ca transistor l emit chung (EC) baz chung (BC) v colecto chung (CC) cn c vo cc no c ly lm im chung cho c u vo v u ra.

Trong cc s tra cu v thuyt minh thng cho cc thng s v c tuyn theo s mc EC hay BC.

i vi s mc BC dng in vo l Ig, dng in ra l Ic, h s khuch i dng in tnh a c xc nh:

a = = _ k _ < ih I c + I b

thc t h s a vo khong (0,9 0,99).

i vi ch xoay chiu, khi im lm vic thay i trn c tuyn

ra, h s khuch ai dng xoay chiu a = trong A I e l bin thin

dng in emit cn AIc l bin thin dng colect.

- S mc emit chung (EC): dng in vo l dng Ig, dng in ra l dng Ic- H s khuch i dng in tnh c xc nh;

tu thuc vo loi transistor p c gi tr t vi chc n hng trm ln. Ic v Ib l gi tr dng in ti im lm vic tnh.

ch xoay chiu h s p c xc inh p = .AIb

Nu bit h s khuch i a c th xc nh c h s p v ngc li:

a = ^ v p = p + 1 " 1 - a

Ngoi ra cn cc tham s khc nh in tr vo, in tr ra, h dn... Cc tham s ca trahsistor cng c th xc nh gn ng bng phng php th da vo c tuyn ca transistor.

40

AI, Ib,

in tri ra R = rcB = ^AI,

transistor lng cc lm vic bnh thng ngoi in p cung cp E cho cc E v c cn mt in p phn cc mt chiu t vo Baz-Emit gi l thin p. in p ny dng thit lp ch mt chiu v im lm vic tnh.

Thin p ban u UggQ s quyt nh dng in tnh, khuch i, mo.

u Bo (0,2 4- 0,6) V i vi transistor Ge UggQ (0,5 4-1,0) V i vi transistor Si.

C ba cch to thin p cho transistor.- To thin p bng dng baz (hnh 2.2a)TTiin p UggQ c xc nh

Suy ra in tr R| cn thit

E -U -BEOBO

Trong : E l in p ngun;UgQ l thin p cn to ra;

IgQ l dng baz xc nh theo UggQ trn c tuyn vo ca transistor.

a) Hnh 2-2. To thin p dio transistor lng cc b)

41

- To thin p bng phng php phn p (hnh 2-2b) Thin p UggQ = Ip.Ra- Suy ra

D _ BEO

trong Ip - dng phn p IR| +R 2

Ip c chn bng (4 ^ 10)Igo

Nu cho trc ggo xc nh c Igo trn c tuyn vo ca transistor.

in tr R| xc nh t biu thc:

BO E - Ip.R2 = E - UggQ

E -USuy ra R, BEO p + l B O

Trong trmg hp c in tr mc emit th trong cc cng thc trn phi tnh n st p mt chiu trn in tr .

- Ch mt chiu v ng ti mt chiu.Xc nh im lm vic tnh 0; khi cung cp cho baz thin p ban u

U beo . th s thit lp dng tnh v in p mt chiu EO To caim lm vic tnh o (Ico UcEo)- im o cng chnh l giao im cang ti mt chiu vi ng c tuyn ng vi dng Igo (hnh 2-3).

a) b)Hnh 2-3. c tuyn vo (a) v c tuyn ra (b)

42

- ng ti mt chiu l s ph thuc dng Ic vo in p ng vi

in tr ti mt*chiu v c xc nh theo biu thc;

u = E - Ic.R=

Cch dng: Cho = 0 -> I,, = , xc inh c im B.

Cho = 0 ^ u = UcE = E, xc nh c im A.

Ni im A vi B c ng ti mt chiu.

- ng ti xoay chiu R_, cng c xy dng trn c tuyn ra nhng i vi in tr ti xoay chiu, tc l khi c tn hiu vo, eng l ng thng v i qua im lm vic tnh o .

Cch dng: T im U gQ trn trc honh, cng thm mt in p bng I(,qR_ , c im A'. K ng thng qua hai im o v A', c ng ti

xoay chiu.E

Cng c th xc nh dng !(, = c im B' trn trc tung, k

ng qua B' v o cng nhn c ng ti xoay chiu.

Trong cc bi tp p dng, c th s dng mt trong hai cch trn, tu tng trng hp c th.

- Transistor trng (FET) l loi transistor c ch to da vo hiu ng trng, l iu khin dn in ca bn dn loi N hay p, nh mt in trng bn ngoi.

C hai loi FET - l J-FET (iu khin bng tip xc P-N) v MOSPET l loi FET c cc ca cch ly bng lp xit. Hnh 2-4 l k hiu JFET knh N v knh p.

GD D

a) J-FET knh N b) J-FET knh pHnh 2-4. J-FET knh N v knh p

43

s - l cc ngun D - cc mng G - cc ca.V phn cc cho cc ca ca J-FET lun l phn cc ngc nn in tr

vo rt ln v dng in ly = Iq = 0; I = Ij.Dng Ij c iu khin bng in p t vo cc ca Uqs v c xc

nh bng biu thc:

uOSKtrong U gs l in p bt k t vo G-S;

Ugsk l in p kho ng vi dng Iq = 0.Quan h gia Ijj v Uqs c din t bng c tuyn truyn t cn quan

h Iq = f(Ds) vi cc tr s Uqs khc nhau c gi l h c tuyn ra. y l hai c tuyn c trimg cho FET, cn c vo , c th xc nh gn ng cc thng s ca FET-

b)Hnh 2-5. c tuyn truyn t (a) v c tuyn ra (b) ca J-FET knh N

H dn ca FET: g = hay mS (milisimen) chi r khi inAUqs V

p t vo cc ca thay i IV th dng I thay i bao nhiu mA.MOSFET gm hai loi: MOSFET knh t sn v MOSFET knh

cm ng.- MOSFET knh t sn; knh dn in loi N hay p hnh thnh ngay t

khi ch to. c tuyn truyn t v c tuyn ra ch dn trong hnh 2-6a, b.

44

b)

Hnh 2-6. c tuyn truyn t (a) v c tuyn ra (b) ca MOSFET knh N t sn

Cn c vo c tuyn truyn t v c tuyn ra c th xc nh gn ng cc thng s ca MOSFET.

- MOSFET knh cm ng: ch khi t vo cc ca in p ngoi (knh N l in p dng), th knh dn in mi hnh thnh v mi c dng in chy qua (hnh 2-7).

Phn cc cho FET.C hai phng php phn cc (to thin p) ph bin cho FET: to thin

p t cp v dng phn p.

b)Hnh 2-7. c tuyn truyn t (a) v c tuyn ra (b) ca MOSFET knh cm hg N

Phcmg php t cp s dng ngay dng j) chy qua Rs to st p v dn qua in tr Rq t vo cc ca G (hnh 2-8a).

45

V 1(3 = 0; Ip = Ij nn Urs = Id-Rs = Uqs; cc (+) t vo cc s v cc (-) t vo cc G.

R - gi l in tr to thin p.Rq - l in tr dn thin p; Ro c tr s ln hng chc hoc trm kQ.

R , = - ^

Hnh 2-8. To thin p cho J-FET

Hnh 2-8b l s to thin p bng phng php phn p.

in p trn cc ca Q c xc nh

G= ~ RaR.+Ra

Uo l in p cc G so vi t.

U gs = U o - U 3 = g - I oR s

Mch phn p cho MOSFET knh N t sn cng tng t nh hnh 2- 8b. Ring i vi MOSFET knh cm ng, vic to thin p c khc vi J- FET, n c to thin p ging nh vi transistor lng cc N-P-N: c th dng phng php hi tip t cc D v cc G hay dng phcmg php phn p (hnh 2-9a, b).

Trong s 2-9a DS = U gs (v dng l o = 0, qua Ro khng c dng chy qua)

UdS E - Iq-Rq

Suy ra Uq5 = E - Iq.R0.

Trong s 2-9b, in p cc ca so vi t.

46

+E

RD

u i-

a) Hnh 2-9. To thin p cho MOSFET knh cm ng N b)

U g = R| +R 2R

^GS ~ ^D' s ~E

R, + R2

in p Uds = E = = E - Id(Rs + Rd)

2.2. PHN BI TP C LI GII

( 5^ Bi tp 2-1. Mt transistor N-P-N mc theo s BC c dng in L = Ig = 50mA; dng in Ic = 45mA.

a) Xc nh h s khuch i dng mt chiu a.

b) Nu mc transistor theo s emit chung (EC), hy tnh h s p.

Bi gii

a) H s khuch i dng mt chiu a

I 49 a = -^ = = 0,98 Ie 50

b) H s p tnh theo a

> = = ............= 491 -a 1-0,98

( 5^ Bl tp 2-2. Mt transistor c dng tnh emit Ig = l,602mA; dng tnh baz Ig = 0,016mA; b qua dng in ngc.

47

a) Xc nh dng tnh colect Ic-b) Tnh h s khuch i p, a.

Bi gii

Tnh dng tnh colect Ic

= Ig - Ig = r,602 - 0,016 = l,586mA

H s khuch ai a = = ^ = = 0,99Ie Ie 1,602

H s khuch i p l _ I - I b _ 1,602-0,016I, IB 0^016

Cng c th xc nh p theo cng thc:

a 0,99

99,125

1 -a 1-0,99= 99

59) Bi tp 2-3. Bit c tuyn vo v c tuyn ra ca transistor mc theo s emit chung EC nh hnh 2-10.Bng phng php th hy xc nh:a) H s khuch i p ti im lm vic A.b) in tr vo = BE-c) H s khuch i a nu mc theo s baz chung BC.d) Nu tn hiu vo Ig thay i, xc nh h s khuch i dng xoay chiu.

- m A )

40Ig=0,4iiA

Ig=03mA

i . .l3=0,2mA

p=0,lmA

0,2 0,4 0,50,6 0,8 Ugg(V) ce(V)

a) b)Hnh 2-10. c tuyn vo (a) v ra (b) ca transistor

48

Bi gii

a) H s khuch i tnh ti im A.

p = ^ = : l = 100BO 0,2 .10

-3

1..^ 0 ,70 -0 ,5 0,65 ^b) in tr vo R v = r, = ---- SS- = , = = 3 ,2 5 k QAL (0,3-0,1)10-' 0,2.10'

_BE _

B

c) Nu mc theo s baz chung BC h s khuch i tnh a c xc nh

a = i = ^ = 0 ,989 1 + p 1 0 0 + 1

d) Khi dng in vo Ig thay i t 0,1 n 0,3mA, tm bin thin dng Ic tng ng trn c tuyh ra, tnh c h s khuch i p xoay chiu.

/

6 _ Ac _ ( 2 8 ,5 - 9 ,8 ) 1 0 -

A L (0 ,3 -0 ,1 )1 0 '= 93,5

(^6^ Bi 2-4. Cho mch khuch i dng transistor nh hnh 2-11

Bit; R c = 5 k Q

p = 5 0

in tr vo Ry = gE = IkO in p vo Uy = UgE = 0,1Va) Xc nh dng in vo v dng in ra.

b) Tmh h s khuch i in p ca transistor.

Bi gii

a) Dng in vo

0,1

Hnh 2-11

= 10"" =0,lm A

Dng in ra:

I = I = p3 = 50.0,1 =5mA

4- 250BTKTINT - A 49

in p ra:

U , = = Ic-Rc = 5.10^5.10^ = 25Vb) H s khuch i in p

. 0,1

Bi tp 2-5. c tuyn vo v ra ca transistor c dng nh hnh 2-12.a) Hy xc nh h dn ca transistor ti im lm vic o.b) Nu bit in p BE thay i 0,2mV, in tr Rc = 4kQ. Hy xc nh in p ra.c) Tnh h s' khuch i in p.

1^=4,2

7 0,8 U,(V)

Ic(mA)50 iA

40|J.A

U=3,Q. 30 A

20|aA

I=10HA

U c e ( V )

a) Hnh 2-12. c tuyn vo (a) v c tuyn ra (b) ca transistor b)

Bi gii

a) H dn ca transistor c xc nh bng phng php th

s = _c_AUbb V

s = A 2 L - =

c) H s khuch i in p

K = H ^ = M = 48 u, 0,2

(^6^ Bi tp 2-6. Transistor lng cc c c tuyn vo v ra mc theo s EC nh hnh 2-13. Cn c vo c tuyn hy xc nh gn ng cc thng s' sau:

a) in tr vo tnh ti im o.b) in tr vo ng.

c) H s khuch i dng in mt chiu p.

d) H s khuch i dng xoay chiu.

250200

50

BE(V)

- I b(^A )40

m A )250fxA

/

3025,

200nA

ISOuA

f ! !

...

15. , L . _ _ iQ A .

--------- 5 / I=50jiA

l U^V)

a) b)Hnh 2-13. c tuyn vo (a) v ra (b) ca transistor lung cc

Bi gii

a) in tr vo tnh

R = r , = 4 k Q'' Igo 150.10-

b) in tr vo ng Rvd

o _ - U be, _ 0 ,6 8 -0 ,5 2^ V a t ^ T TAI B Ib, - I b. (200- 100)10

= l,6 k Q

c) H s khuch i dng mt chiu p

51

~6

I I50.10-*

d) H s khuch i dng xoay chiu p_

AI3

AIb= I3 -Ib_ =(200-100)10-^ = 100.10

Tm AIc tng ng trn c tuyn ra

I =30mA; = 15mA

AIc = (30-15).10l

(200-100)10-"

(6 ^ Bi tp 2-7. Oio mch in nh hnh 2-14. Nu bit dng Ico =5mA; h s p = 100; 5V;thin p Ubeo = 0,6V; E = lOV.

a) V cc dng in mt chiu chy trong mch.

b) Tnh in tr R ec) in p Uc so vi t.

Bi gii

a) Dng in mt chiu chy trong mch nh ch n trong hnh 2-14.

Ie = Ic + Ib

b) in tr to thin p R| c xc nh.

Hnh 2-14

R,E - U ^ E -U ^ o 10-0 ,6 9,4

Ibo co q-3 5.10 *p 100

188ka

c) Tnh in tr R,

52

I I 5.10-

d) in p Uc so vi im mass chnh l in p UgQ

U c = U ,,o = 5V

@ Bi tp 2-8. Cho mch in nh hnh 2-14. Nu bit R, = 220k0; Rc = 2kQ; = 50; ggQ = 0,5V. Hy xc nh cc thng s tnh:dng Ig, Ic, Ie, in p Uceo

Bi gii

a) Xc nh dng Igo

R, 220.10' 220.10'

b) Dng Ico = l = 50.34, lK = 1,7mA

c) Dng 1 0 = Ico + I b o = 1 >7 + 0,0342 = 1,7342mA.

d) in p U go

UeEo=E-Ico.Rc=10-l,7.10"'.2.10^=6,6V

Bl tp 2-9. Mch in nh bi 2-7 nhng mc thm in tr Re emit v bit st p trn in tr ny l IV.

a) Xc nh tr s' R|, Rc, Re-b) Xc nh in p Uc U so vi im mass ca my.

Bi gii

a) Xc nh Re

U re = I e o - R e = 1 V

_ IV IV 1Suy ra Rb = = = ^ ------- = 198Q

Iro + 5 .10 '^ + ~ 10-^ 100

- in tr R

53

R _ _ E - ^ beo -U r , _ 1 0 -0 ,6 -1' I bo I bo 5.10-^

168kQ

- in tr Rc

CO C ^ CEO ^R,

800Q

V. V.V.V/ IVJ.-

Suyra: R , = =leo 5 .10-^

b) in p Uc = E - IcoR c=10-5.10l800 = 6V

h a y U c = U ,, /+ U ,^ =5 + l = 6V

in p Ub = Uggo + R = 0,6 + 1,0 = 1,6V

( e ^ Bi tp 2-10. Cho mch in nh hnh 2-15. Bit R, = 300kQ; Rh = 2,7kQ; p = 100; 3,o =

0,5V ;E= 12V.

a) Xc nh cc tham s tnh.

b) Nu mc R, = 2,7kQ hy tnh in tr ti xoay chiu.

Bi gii

a) Trc ht xc 'nh dng tnh baz I

R+E

R. R.

Hnh 2-15

BO '1 ' '-'BEO ' ^EO^'E BEO

( y I e o = I co + I b o = I b o + P I b o = 0 + P)Ibo)

E -U .. 12 -0 ,5Suyra l30 = BEO _

R, +(1 + P)Re 300.10"+(1 + 100).2 ,7.10^= 20A

- Dng tnh 1^0 = lOOIgo = 100.20^iA = 2mA

- Dng tnh 1^0 = Ic + Ibo = 2 + 0,02 = 2,020mA.

- in p trn cc E, cc c v B so vi im mass:

ra

54

Ue = Ieo-Re = 2,02.10-^2,7.10" = 5,45V

in p U c = E = 12Vin p Ub = Ue + = 5.45 + 0,5 = 5,95V

b) Nu mc R, = 2,7kQ th in tr ti xoay chiu mch emit.

R = R / /R = A = A Z : ^ = l , 3 5 k Q ' Re+R, 2,7 + 2 ,7

Bi tp 2-11. Cho mch khuch i dng ansistor lng cc nh hnh 2-16a. Bit E = lOV; Rc = 5kQ; Re = 0,2R R, = 85kO; R , = 15kQ; = 4 V ; Ico c ; p = 50-

a) Hy xc nh cc tham s tnh ca transistor.b) im lm vic tnh o v dng ng ti mt chiu.

a)

a) C th coi

Suy ra:

Hnh 2-16

Bi gii

EO ~

- Dng tnh baz IgQ:

- Thin p

Ur0 Ip-R ~ RE ~ -----------Rt ~^E0'^EBEO p 2 RE 2 EO E

10-M0^=0,5V(15+ 85). 10

b) To im lm vic tnh O: = lmA;UcE0 = 4 V . t) dng ngti mt chiu cn xc nh mt im na. T biu thc phng trnh ng ti mt chiu.

U = E -I c .R cCho Ic = 0 u = E = lOV (im A trn trc honh) ni qua im A

Bi gii

- in tr ti xoay chiu R_.

R. = R^//R ,= ^ = ^ = 2,5kQRc+R. 5 + 5

- ng ng ti xoay chiu R_ cn xc nh mt im trn trc honh hay, trn trc tung ri ni vi im lm vic tnh o. T imcng thm mt on ng vi in p bng IcqR-

IcoR_= 1012,5.10^ = 2,5V

ta c im A' trn trc honh (hnh 2-16b).

Ni im A' vi im o v ko di s c ng ti xoay chiu. Cng c th dng ng ti xoay chiu bng cch xc nh im B' trn trc tung

E 10ng vi dng I = = r = 4mA, ri ni im B v o .

& R_ 2,5.10'

56

(m ) Bi tp 2-13. Cho mch in nh hnh 2-16a. Nu E = lOV; CEO = 4V ; Rg = 0,1 Rc, Ico=20mA; UgQ=0,7V, t c tuyn vo ca transistor ng vi UggQ = 0 ,7 V , tm c IgQ =0,2m A .

a) Xc nh tr s cc in tr Rc, Re, Ri, R-> m bo c cc thng s trn.b) Xy dng ng ti mt chiu.

Bi gii

a) Xc nh tr s cc in tr T biu thc:

E = CEO EO E * CEO( y c th coi I Q IgQ n gin cho vic tnh ton).

Suy ra + R . = - - - ggg = = 300Q l 20 . 10

Re 0,1 Rc = l,lR c ~ 3000

M = 272,701,1

Rg = 0 , lR c = 2 7 ,2 Q .

- in tr Rj c xc nh theo biu thc:

~ ' BEO

Suy ra

( y chn dng phn p Ip = 5 Io )

R 0.7 + 20.10-.27,27..^ 5.1 5.0,2.10-

- in tr R| c xc nh t biu thc: I

Ri(Ip+ I^q) = E - IpR2 = E - UggQ- IgQRg

" u r a r E - U o - I ^ R , _ 10 - 0,7 - 0,5 4 5 _ ,5 l" + I 6.0,2.10-

57

b) xy dng ng ti mt chiu, ngoi im lm vic tnh o bit 0(20mA, 4V) cn xc nh mt im na.

T phng trnh UcE = E - Ic(Rc + Re) nu cho UcE = 0 th

E 10= 0,0333A = 33,3mA

R. + Rg 300

ta c im B trn trc tung, ni B vi o v ko di s c ng ti mt chiu (hnh 2-17).

Hnh 2-17

070) Bi tp 2-14. Bit c tuyn truyn t v c tuyn ra ca mt J-FET knh N nh hnh 2-18.

a) Xc nh trn th dng b ho Ij5ss v in p kho U qsk-

b) Tnh dng Iq ng vi cc gi tr Uos = OV; Uos = -2V; Uos = -4V vU g s = -6V.

Bi gii

T c tuyn truyn t Id = f ( G s ) hnh 2-18a, dng bo ho Ipss ng vi U q s = ov, Ij5ss = 15mA.

in p kho U gsk ng vi Iq = 0 , trn th xc nh c Uqsk = -8V.

b) Dng Ij3 ph thuc vo in p QS v c xc nh bi biu thc;

58

a) b)Hnh 2-18. c tuyn truyn t (a) v c tuyn ra (b) ca J-FET knh N

Id = Idss(1 - ^ ) 'U GSKUgs = 0 ^ Id = Idss = 15mA

Uos = -2V-^ = 15 (1 - = 8,437mA.-0

U gs = -4V ^ l o = 15 = 3,75mA.o

Ucs = -6V ^ Id = 1 5 (1 - )' = 0,9375mA.

( 7 1 Bi tp 2-15. Cho mch in dng J-FET knh N nh hnh 2-19. c tuyn ca J-FET nh bi 2-14.

Bit E = 15V; im lm vic tnh c chn ng vi Rd = IkQ.

a) Xc nh tr s R.b) Xc nh thin p Uqsq .

c) in p trn cc mng Up.Bi gii

a) in tr Rs c xc nh theo biu thc:

U

R - - U q d k - 8V 21 2.15.10-^

= 266Q

+E

H h -p -H i

Hnh 2-19

ra

59

b) Thin p = R Jn = 266.7,5.10'" 2 VGSO S- D

(y I t ,= % = ^ = 7,5mA) 2 2

c) in p UqU d = E - I d. Rd = 15 -7 ,5 .1 0 ^ 1 0 ^ = 7 ,5V

Bi tp 2-16. Cho mch to thin p cho J-FET knh N bng phng php phn p nh hnh 2-20. Bit: E = 15V; R, = 600kQ; R, = 150kQ; R = l,5kQ; Rs = IkQ; 5mA.

a) Xc nh Uas-b) Dng cc mng Ip.c) in p trn cc mng Up.

Bi giia)

GS R| +Rj (600 + 150)10

E

Hnh 2-20. Mch to thin p cho J-FET

5.10"\10' = - 2 V

,R ,=15 150 = 3Vin p trn cc ca U f - _

R ,+ R , " 600 + 150

in p trn cc ngun Us = Q - U qs = 3 - (-2 ) = 5V. hay Us = Is.Rs = Id-Rs = 5.I0 M 0 = 5Vb) Xc nh li dng cc mng Ip

I. = L = = = 5.10-'A = 5mA Rs 10'

c) in p trn cc mng UpUd = E-Id.Rd= 15-5.10M,5.10^ = 7,5V

in p U ds = Uo - U s = 7,5 - 5 = 2,5V.( t ) Bi tp 2-17. Cho mch in dng MOSFET knh t sn nh hnh

2-21 a v c tuyn truyn t nh hnh 2-21b. Bit: E = 12V; Ro = 200kQ; u 3 , 5 V .

a) Hy xc nh tr s in tr R| to thin p yu cu U qsq= -2V.

b) Xc nh dng 1,30

60

a) b)

a) GSO

Hnh 2-21. Mch in (a) v c tuyn truyn t (b)

Bi gii

= - U30 = -2 + 3,5 = 1,5V

V dng lo = 0 nn c th vit

Suy ra

R .=

R. =

R, +R qR.

URG

G

12 200Thay s: R, 200 = 1400k0 = 1,4MQ

' 1,5

b) Dng 1^0 = 5mA ng vi Q5Q = -2V (xc nh trn th 2-2 Ib).

( 7^ Bi tp 2-18. Nh bi 2-17. Nu chn im lm vic ng vi U qsq = -2 V , dng IpQ = 5mA; in tr Rjj = l,2kQ.

a) Hy xc nh in p Uq.b) Tnh in tr Rs.

c) Khi in p vo thay i trong khong -2V 0,5V, hy xc nh bin in p ra v h s khuch i K.

Bi gii

a) in p Ud = E - IdqRo = 12 - 5.10M,2.10^ = 6V.

b) in tr Rg.

61

3,5Ido 5.10-^

= 7 0 0 0

c) Khi in p vo U qs thay i trong phm vi -2V 0 ,5V, xc nh trn th 2-2 Ib dng Id thay i t 2,5mA n 6,25mA, nh vy bin thin dng Id t nh - nh

AI = 6,25 - 2,5 = 3,75mA in p ra (nh - nh) s bin thin

u = AId-Rd = 3,75.10-M,2.10^ = 4,5V H s khuch i in p

1

tp 2-19. Mt MC^PETkih t sn c c tuyi ttuyi t nh Hnh 2-22.

a) Cn c vo c tuyn xc nh h n ti vng ngho GS = -2V v ti vng giu QS = +3V.

b) Cho nhn xt.

iD(mA)'

15vng giu/ M

107,55

vng ngho i l '

-4 -3 -2 -1 1 2 3 4 Uqs(V)

Hnh 2-22

Bi gii

a) Ti vng ngho, theo th

U g s = -2V -> Id = l,2mA Ugs = -IV Id = 2,5mA

A U os=lV

AIp = 2,5mA - l,2mA = l,3mA

62

H dn g = -" - - = l,3^^^hay l,3mS (milisimen) AUqs V

Ti vng giu Uos = +3V -> Id = lOmA

Ugs = +4V Id = 15mAAl 15-10 _mA, _ H dn g = = = 5 hay 5mS

AUGS 4 - 3

b) Nhn xt: vng giu h dn ca MOSFET ln hn vng ngho.

Bi tp 2-20. Cho mch in dng J FET knh N nh hnh 2-23. Bit Ro = 1,5MQ; Rs = 300Q; R =2,2kQ; R, = 15kQ; E = 15V.a) Xc nh in tt ti xoay chii R_.b) H dn ng ti Uqs = -2V.c) Tnh h s khuch i Ky.d) Tnh in p ra n.u Uv = 0,5V.

B gii

a) in tr ti xoay chiu R_

b) H dn ti gc:

m oGSK

H dn ti im Ucs = -2V.

U m mo 1 GSUGSK .

= 5mS 1 -2-6

= 3,33lA

c) Tnh h s khuch i

K = gR_ = 3,33.10-'. 1,92.10' = 6,393.

63

d) Xc nh in p ra

Uos = OV; U gs = +2,0V; Uos = -2,0V.

Bi gii

- Khi Uq5 = 0 > Ij) = Idss 15mA. -Khi

Ucs = +2V ^ I ^ = I s3 1 u

- Khi Uqs = -2V -> In = 15.10

GSK

-3

= 15.10-3-6

= 26,66mA

-6= 6,6mA.

Bi tp 2-22. Mt MOSFET knh N cm ng c c tuyn truyn t v mch in nh hnh 2-24.a) Hy xc nh bng phng php th h dn g ti im lm vic 0(8V, 7,5mA).

b) Tnh tr s Rq.c) Tnh in p ra nu in p vo bin thin IV.

.+15V

a) Hinh 2-24 b)

64

Bi gii

a) Xc nh h dn g.

gm = . ?:. ,2 ,5 i^ h a y 2 ,5 m sAUGS 8V -7Vb) in tr Ro

= - p i . = J 5 _ 8 _ ^ chn R =.lkQI, -3DO 7,5.10

(yUos = UGs = 8V vIc = 0).c) Xc nh U,, nu Uv = 1V.

u = Ki .Uv = g.Ro.Uv = 2, 5. ^. 0M,0 = 2,5V

( t^ Bi tp 2-23. Cho mch in dng J-FET knh N nh hnh2-25. Bit;E = 12V; Rg = IMQ;

c5q = 1,2V . in p trn Rs,Urs = 0,2E = 2,4V. H dn

g = 5 . in tr cc mng

ngun r = 200kQ.= 0, Ir, = 0, 1 ,200kQ = 20kn.

a) Tnh in tr R.b) Tnh h s khuch i Ky.

Bi gii

a) Tnh R,R.

Suy ra R. =E.R,

^RS

R| +R q

E

= 10'12

1

vUks- U oso

= 9MQ.

-1

b) H s khuch i Ku.

Ku = m- Rd = 5.10 ^20.10^ = 100.

5- 250BTKTNT-A 65

Chng 3

CC MCH KHUCH I TN HIU B

3.1. TM TT PHN L THUYT

phn tch v tnh ton cc thng s k thut i vi b khuch i in t dng transistor lm vic ch tn hiu b thng da vo cc loi s tcmg ng.

Transistor thng c biu din bng hai loi s tng ng:

- Loi th nht gi l s tng cmg vt l hay s tofng cfng hnh T v cng c tn gi l s tng ng (The g transistor model).

- Loi th hai c gi l s tng ong tham s' bao gm cc tham s tr khng, in dn hoc hn hp.

C hai loi s tng ng ca transistor c th coi l khng ph thuc vo tn s n mt phm vi kh cao:

- i vi cc loi transistor lng cc (BJT) khi tn s tn hiuf ,< ( 0 , l - f 0,5)f,.

- i vi cc loi transistor hiu ng trng (FET) khi tn s tn hiuf ,< (1 0 ^ 150)MHz.

phm vi tn s cao hn nhng s liu trn, khi s dng cc loi s tng ofng phi c la chn mt cch thch hp v khng c b qua nh hng ca cc t k sinh (Cj(;s) bn thn transistor n s truyn t tn hiu qua n.

Vi mi kiu mc i vi transistor c ba h c tuyn Volt-Ampe quan trng: h c tuyn vo, h c tuyn ra v h c tuyn truyn t.

C th xy dng ng ti mt chiu (R.) v ng ti xoay chiu (R_) trn cc h c tuyn c bn ca transistor v xc nh cc tham s mt chiu cng nh xoay chiu ca tng khuch i in t.

6 6 5-250BTKTINT.B

Cc thng s k thut c bn i vi tng khuch i in t dng transistor bao gm; tr khng vo (Ry), tr khng ra (R a), cc h s khuch i in p ( K u ) dng in ( K ) , cng sut ( K p ) .

H s khuch i nhiu tng ghp lin tip bng tch cc h s thnh phn.

3.2. BI TP C LI GII

( 8 Bi tp 3-1. Cho tng khuch i dng BJT nh trn hnh 3-1.

a) Xc nh r .

b) Xc nh tr khng vo ca tng Ry.

c) Xc nh tr khng ra ca tng (vi fo = oo)

d) Xc nh h s khuch i in p Ku (vi Q = oo)

e) Xc nh h s khuch i dng in K (vi Q = o)

E .J 2VCO

II uCj 10|iF

p=100

r=50kQ

Hnh 3-1

Bi gii

Chn transistor T loi Si v thin p Uggo =0,7V

a) Dng tnh IgQ s l:

12V -0,7V ,Ibo = = 24,04^iA

Rg 470kQ

Dng tnh IgQ s l:

1,0 =(1 + P)l30 = (l + 100)24,04.10-'A = 2,428mA

in tr r, c xc nh:

67

1 0 2,428.10-'b) Tr khng vo c tnh:

Ry Rb // TvTtrong Tvt - tr khng vo ca transistor

fy = pr,= 100.10,71 = l,071kQ

Ry = 470//1,071 = l,069kQ.c) Tr khng ra ca tng c tnh:

R = Rc / / Q = Rc / / 0 = Rc = 3kQ .

d) H s khuch i in p ca tng:

r, 10,71

e) V Rg > lOrvT = lOp.r, (470k0 > 10,71k0) nn K p =10 0

Bi tp 3-2. Tnh ton lp li cho bi tp trn*hnh 3-1 vi Q = 50kQ.

Bi gii

Ta nhn thy cc thng s trong hai cu a, b s khng c g thay i nn;

a) r,= 10,710b) Rv= l,071k ac) Tr khng ra ca tng c tnh:

= Re // ro = 3 // 50 = 2,83k.

d) H s khuch i in p ca tng.

-264,24r. 10,71

e) H s khuch i dng in KjY- _ P-Re-rp : 100 .470 .50 ^3

(ro+R^XRg + r ) (50+ 3)(470 + 1,071)

C th tnh K: theo biu thc khc:

68

K , = - K > = 2 H 3 1 ) W 9 =94,163

Bi tp 3-3. Cho tng khuch i dng transistor lng cc (BJT) nh trn hnh 3-2. Hy xc nh:

R

n , lO iF

^3 6,8kQ+E^22V

56kn

^1

T R

R,

uc'lOjiF

X - p=90R

>8,2kf n lORp th tr khng ra c th c tnh:

R = R o//R o = RD = 2kQ

e) Ku = -g^.Ro = -1,63mS.2 = -3,26.Khi b qua nh hng ca vi r lORp.Khi tnh n r th:

Ku = -g,(Rc // ra // Rd) = -1,6ms( 1OMQ // 50kQ // 2kQ) = -3,21.

( 9^ Bi tp 3-16. Qo tng khuch i dng J-FET nh

UoD 30V

trn hnh 3-13. Hy xc nh in tr ti mt chiu Rp ca tng vd h s khuch i in p Ku = 10.

Bi gii

Vi Rs = O trn s hnh 3-13 ca u bi ta c u Q5 = o v v iu c ngha l:

R

II T

Rg > lOMn Ip55 = 1 Oll A Up = -4V g, = 20tiS

Hnh 3-13

Ku = -gn,Rn. = -gm Rra = -gmCRo // r

Mt khc ta c:

1 1rd= =g. 20 .10 -

Khi : Rd // r, = Rd // 50kQ = 2kQ

= 50kf

RoSOkQR^+SOkQ

RoSOkQ = 2(Rd + 50)kQ

Vy Rj) = 2,08kQ v chn in tr R theo tiu chun s l Rjj = 2kQ.

(% ) Bi tp 3-17. Cho mch khuch i dng J-FET nh trn hnh 3-14.

Hy xc nh in tr Rj) v Rs vi Ku = 8 v Uqs_ = Up = - I V . Bit

thm: Idss = lOmA; Up = -4V; gj = 20|J,S.

DSS * mAU p = - 4 V

Ga = 20 lS

Hnh 3-14

Bi gii

T- ' _ 2Idss _ 2.10mATa c; - = 5mSU,

v g = g ( l - ^ ^ ) = 5 m s ( l - ^ ) = 3,75mS

mt khc: Ku = -g(RD // r

nn

Rd // ra = Rd // = Ri, / / - ^ = Rd //50kQ = 2,13kQ gd 20|aS

T ta xc nh c Ro = 2,2kQ (ng theo tiu chun).

xc nh in tr Rs c th xut pht t biu thc;

' GSO ~ DO S

DO Dss(uGSO \2 _Up

= lOmA-4

= 5,625mA

Vy Rs = = 177,80IDO 5,625.10

Chn theo bng in tr tiu chun Rs = 180Q.

{^9^ Bi tp 3-18. Qio tng khuch i dng J-FET nh trn hnh 3-14 (xem s liu bi tp 3-17). Hy xc nh gi tr R|5, Rs khi khng c t Q.

Bi gii

Khi khng c t Cs trn mch, cc i lng tnh ton cho ch mt chiu ca tng khng c g thay i ngha l: QSO = - I V ; Ij3 = 5,625iiA;

Rs = 180f! (nh trong bi 3-17).

Biu thc tnh h s khuch i in p Kjj s l:

m^D" l + Sn,Rs

8 =- 3,75mS.Rj3

l + 3,75.10"^180_ 3,75mS.Rp

1+0,675

t tnh c Rq s l:

13 4R ^ = - - = 3,573kQ 3,75mS

Chn in tr Rp theo tiu chun l Rp = 3,6kQ.

82 6- 250BTKTINTL

( 98 Bi tp 3-19. Cho b khuch i in t nh trn hnh 3-15. Hy xc nh K ; Ry; Rn.; u^; u vi U gso= -1 ,9V ; Ioo=2,8mA v R, = lOkQ.

Ipss = lOmA; Up = -4V; T v T2 cng loi v c cng cc tham s.

ra

Hnh 3-15

Bi gii

m o_ _ 2.10mA

m S m o ^ ^

U

u 4V = 5mS

Up) = 5mS 1 -1>9

4 J= 2,6mS

Ku. = Ku, = = -Ri = -gRs = -2,6mS.2,4kQ =H s khuch i Ku s l:

K ,=K ,,.K ^ ,^=(-6,2)(-6 ,2) = 38,4

in p ra s l:

u = Ky.Uv = 38,4. lOmV = 384mV

Tr khng vo ca b khuch i l:

Ry = Rg = R2 3,3MQTr khng ra ca b khuch i l;

- 6,2

83

R , = R5 = = 2,4kD.Khi mc ti R, = lOkQ, in p ra trn ti s l:

u, = u =i^384mV = 310mV R+R, 2,4 + 10

( 9^ Bi tp 3-20. Cho b khuch i in t dng BJT nh trn hnh 3-16 vi Ub = 4,7V; Ue = 4V; Uc = i 1V; Ie = 4mA. Hy xc nh: K ; u; Rv; rI v u, khi mc ti R, = 1 OkO.

R

10)iF h -Uv c,

15kQ

25 iV R < 4 J ^

:R,2,2ka * 5

q 10nF P=20

R7 > 2,2kO

+E,,20V

4,7kn1

C ,1 0 |iF

p=200

^620mF

Hnh 3-16

Bi gii

Trc tin ta xc nh in tr Tg

26mV 26= = 6,5Q

H s khuch i n p tng 1:

r. _ R _R c(//R 4//R 5//P-r.)* u, ~

Te Te2,2kQ//(15kQ//4 ,7kQ//200.6,5Q

y

6,5QR,, = R 3 //(R ,//R ,//p .rJ

= -102,3

84

H s khuch i s l:

. = _ ^ = _ ^ = _ ^ = _ 2 : ^ . _ 3 3 8 , 4 66,5

Ku = Ku, = (-102,3){-338,46) = 34624

u = Kij.Uv = 34624.25^iV = 0,866V Tr khng vo ca b khuch i l:

Rv = R, // R, // pr, = 4,7kQ // 15kQ // 200.6,50 = 953.6Q Tr khng ra:

Rc ^6 ~ 2 ,2kQ.Khi mc R, = lOkQ in p ra trn ti s l:

u = ^ U = 1 ^ 0 .8 6 6 V = 0.71V

> 2 ,4 k n ^3

0 ,05^F

4,7kQ 4 = .1 '5 100fxF

Hnh 3-17

Bi gii

H s khuch i ca tng th nht:

85

Ku. = //R v,) = -2,6mS(2,4kQ//953,6D) = -1,77

H s khuch i K s l:

K^^=KK = (-l,77 )(-338 ,46) = 599,1

in p ra u = K^.Uv = 599 ,l.lm V = 0,6V

Tr khng vo Rv = Rq = 3,3MQ

Tr khng ra R,, = Rc = 2,2kQ = R5.

(10^ Bi tp 3-22. Cho tng khuch i cascode nh trn hnh 3-18. Hy xc nh Ku ca tng vi = 4 ,9V ; U 3 = 10,8V ;

!(, = Ic = 3,8mA = 1 = Ig; P| = p2 = 200; T = T2 = T (ging nhau).

p, = p, = 200

T, = T, = T

(ging nhau)

Hnh 3-18

Bi gii

26mV 263,8

= 6,8Q

86

Vy K =K ., .K = -2 6 5 .'

( 1 ^ Bi tp 3-23. Cho tng khuch i dng transistor Darlington nh n hnh 3-19. Hy xc nh h s khuch i dng in K|.

Bi gii

Ta c th v li s tng ng mch in nh trn hnh3-20 di y:

_ Pd^b

8000.3,3.103,3.10^+8000.390

= 4112

Hnh 3-20( 1 ^ Bi tp 3-24. Oio tng

khuch i dng transistor Darlington nh trn hnh 3-21. Hy xc nh Rv; R; K|; Ku vi = 3kQ.

87

Bi gii

Ry = Rg // (r^ + p,p2.Rc) = 2MQ // (3kQ + 140.180.75Q) = 974kQ.

K;=p.p2R 9 1 a6

= 140.180( - t) = 3,7.10^Rg +Rv 2.10"+974.10^

R = -!h _ = i i ^ = 0,12Q p,p2 140.180

v K = - J M ^ = _ 1 ^ 1 * ^ = 0,9984, p,p2Rc+r 140.180.75+3000

( ^ Bi tp 3-25. Cho mch in dng J-FET nh trn hnh 3-22 (mch to ngun dng). Hy xc nh dng Id v u khi:

a)RD=l,2kQ.

b) Rd = 3,3kQ.Vd Idss = 4mA v Up = -3,5V.

Bi gii

T mch in cho khi Uqs = ov.Ij3 = I0SS 4m A.a) = E dd - IdRd = 18V - 4mA.l,2kQ = 13,2V.

Edd18V

R,

u_

Hnh 3-22

88

b) u , , = Edo - IdR d = 18- 4 .3 ,3 = 4,8V .

Bi tp 3-26. Cho mch in dng BJT

nh trn hnh 3-23 (mch to ngun

dng). Hy xc nh dng in I.

Bi gii

Chn transistor loi Si vi Ugg = 0,7V.R,Ta c: g =

R, 4-R2

5,1 (5,1 + 5,1)

(_20) = -10V

S.lkQ-

+E^ -20VcC

Hnh 3-23

Ue = U 3 -U bh = -10-0 ,7 = -10,7V

I = I , = l ^ = d Z z m = 4,65mA. R. 2

(1^ Bi tp 3-27. Cho ngun dng

dng transistor v zener nh trn

hnh 3-24. Hy xc nh dng

in I vi u , = 6,2V.2.2kn'

Bi gii

Chn transistor loi Si vi

l,8kQ

+E. -18V

Ube = 0,7V.

Ta c:Hinh 3-24

R 1,8

(1^ Bi tp 3-28. Cho mch in ng transistor nh trn hnh 3-25 (mch gomg dng). Hy xc nh dng in I.

89

Bi gii

Chn transistor T| v T2 cng loi Si. E - Tac: 1 = 1

(12-0 ,7)1,1

R

= 10,27mA.

108) Bi tp 3-29. Cho tng khuch i vi sai dng BJT nh trn hnh 3-26. Hy xc nh in p ra u. Vi = 20kQ; Pi = P2 = ^5.

Bi gii

Chn transistor T| v T, loi Si vi Ube = 0,7V.

Ta c:E. - U

h =BE

R

9 -0 ,7j = 193 iA

= 96,5nA.

43.10

Dng colect; l 193|aA

2 2

T ta c Uc c tnh:

Uc = Ecc - lRc = 9 - 96,5.10 ^47.10' = 4,5V. in tr c tnh;

1-3

Hnh 3-26

96,5.10

H s khuch i in p Ku s l;

K = ^ = ^ = 87,4 2r 2.269

90

u = Ku-Uv = 2.10187,4 = 1,I75V.

(1^ Bi tp 3-30. Hy xc nh h s khuch i tn hiu ng pha ca tng khuch i vi sai dng transistor trn hnh 3-26.

Bi gii

T biu thc c bn tnh ton cho h s khuch i tn hiu ng phai vi tng vi sai ta xc nh c Kc nh di y:

K PRc , 75.47 Uv r^+2(p + l)Rg 20 + (l + 75)2.43

(1^ Bi tp 3-31. Hy xc nh Kc ca tng vi sai cho n hnh 3-27 di y:

Vy u s l:

T, &T p, = p2 = 75VTl VT IcC

Tap3 = 75

r3 = Re = 2 0 0 k

Bi gii

Transistor Tj kt hp vi cc linh kin mc trn mch to thnh mt ngun dng nhm nng cao tr khng mt chiu. Rg v v th khi thay cc gi tr vo biu thc tnh Kc ta c:

K , = ------- = 24,7.1 0-' ry^+2(l + p)RE 11 + 2.76.200

91

3.3. BI TP

0 Bi tp 3-32. Cho tng khuch i dng BJT mc EC nh trn hnh 3 28. Hy xc nh Rv; R; Ku, Kj

a) vi Q = 40kQ

b) vi Tq = 20kQ.

:60

Hinh 3-28

( 1 ^ Bi tp 3-33. Cho mch in dng transistor nh trn hnh 3-29. Hy

xc nh E c c sao cho Ku = -200.

( ^ Bi tp 3-34. Cho tng khuch i ng transistor nh trn hnh 3-30.

Hy xc nh r ; Ry; R; K ; K| vi:

a) Tq = 50kQ

b) ro = 25kQ.

92

+E^16V

R| :3,9kn

I , I I - - - *u,q I^ F

raP=100

Hinh 3-30

(1 ^ Bi tp 3-35, Cho tng khuch i dng BJT nh trn hnh 3-31. Hy ?CC c) Ku; K,

+Ecc20V

Hp=80r.=40kQ

Hnh 3-31

Bi tp 3-36. Cho mch in dng transistor nh trn hnh 3-32. Hy xc nh R v ; R; K ; K, v u,, khi Uy = ImV.

93

( l ^ Bi tp 3-37. Cho tng khuch i dng BJT nh trn hnh 3-33. Hy xc nh Ib; Ic; r ; R v, K^; K.

(1^ Bi tp 3-38. Cho mch khuch i dng BJT nh trn hnh 3-34. Hy xc nh r ; Rv, Rra K|.

T+6V -IOV a = 0,998R ^6,8kQ R ^ 4 ,7kn

v Iv \ /l----*u

R

ra

Hnh 3-34

94

(b) Bi tp 3-39. Cho mch khuch i ng BJT nh trn hnh 3-35. Hy^ xc mh Ku; K,.

+8V

ra

-5V

Hnh 3-35

Bi tp 3-40. Cho tng khuch i dng BJT nh trn.hnh 3-36. Hy xc nh r,; Rv; R,,; K; K;.

t E.. 12V

R. 220k

,-II-

R,3.9kQ

l . p=120

R,r=40k

Hinh3-36

Bi tp 3-41. Cho tng khuch i dng BJT nh trn hnh 3-37. Vi r, = lo; p = 200; =-160; K = 19; To = )kn. Hy xc nh R K Ecc.

R.

u.-l-

VSAr

68kQ > 2,2kf

^+Ecc 18V

Hnh 3-38

Bi tp 3-43. Qio tng khu&h i dng BJT nh t-n hnh 3-39 vi h2| = -0 ,992;

h =9,45Q ; h,, = 1 ^ ^ . h 22,, Y

Hy xc nh Rv; R; K ; K ; a; p; r ; Tq.Bi tp 3-44. Cho tng

y-R

H l -10iF V /

R ^l,2kQ

T 4V

lO iP 2,7kQ ^

12V R.

Hnh 3-39

khuch i dng J-FET nh trn hnh 3-40. Hy xc nh Rv; R; Kjj vi Idss - lOmA; Up = -4V; = 40kQ.

Edd18V

Rol.SkQ

Hnh 3-40

96

( ^ Bi tp 3>45. Cho tng khuch i dng J-FET nh trn hnh 3-41Hy xc nh Ry; R; Ku vi = 3000|iS v gd = 50|aS.

( ^ Bi tp 3-46. Hy xc nh Rv; R; Ku ca tng khuech i dng J- FET nh trn hnh 3-41 (xem bi 3-45) khi ngt t Cj ra khi mch.

( l ^ Bi tp 3-47. Cho tng khuch i dng J-FET nh trn hnh 3-42. Hyxc nh Rv; Rn,; u vi Uy = 20mV; loss = 12mA; Up = -3V; T = lOOkQ.

ra

Bi tp 3-48. Hy xc nh Rv; R; u ca tng khuch i dng J FET nh trn hnh 3-42 (xem bi' 3-47) khi ngt t C3 ra khi mch.

@ Bi tp 3-49. Tnh ton lp li cho bi 3-47 khi thay r., = 20kQ.

(1^ Bi tp 3-50. Tnh ton lp li cho bi 3-48 khi thay = 20kQ.

7. 250BTKTINT.A 97

^3^ Bi tp 3-51. Cho tng khuch i mc GC dng J-FET nh trn hnh 3-43.^ Hy xac nh Rv, R; u^; vi Uv = 0,lmV; Icss= 8mA; Up = -2,8V; = 40ka.

ra

Hinh 3-43Bi tp 3-52. Cho tng khuch i dng DMOSPET nh n hnh 3-44. Hy xc nh bit gj = 20pS; Uy = 2mV; I ss = 8mA; Up = -3V.

41 *u

Hh

RG>10Mf

Hnh 3-44(132) Bi tp 3-53. IO tng khu&h i dng D-MOSFET nh trn Knh 3-45. Hy

xc nh Rv, R; Ky. Bit = 6kQ; Icss = 12mA; p= -3,5V; Edd = 22V.

Eoo 22V

^ o i.sk n

u.'ni

Rq!lOMQ' R

100 .Hnh 3-45

98 7-250BTKTINT-B

(1 ^ Bi tp 3-54. Tnh ton lp li cho bi tp nh hnh 3-45 vi = 25kQ.

( 1 ^ Bi tp 3-55. Cho tng khuch i dng D-MOSPET nh trn hnh 3-46.Hy xc nh vi Uv = 4mV; gj = 35|0,S; g = 6000|J,S.

Eoo_________t 'DD

[ n91NK > 3

. E^d 20VR,

R 22MD r-AAAr-

\QkQ------- i H

2ra

Hinh 3-48

( Bi tp 3-60. Hy xc nh u ca tng khuch i dng E-MOSPET cho trn hnh 3-48. Bit: Uv = 4mV; Ut = 4V; 1 ^ = i ; = 4m A ;

- U , 3 _ = U ; s = 7 V ; g , = 2 0 ^ i s .

Bi tp 3-61. Oio tng khuch i dng E-MOSPET nh trn hnh 3-49.

Hy xc nh u vi U v = 0,8mV; = 40kQ; T = 3V; k = 0,4.10 \

Bi tp 3-62. Cho mch khuch i dng JFET nh trn hnh 3-50. Hy xc nh Rjj vi: Iqss = 8mA; U p = -2,5V; gd = 25fiS; Ku = 8.

100

ra

Bi tp 3-63. Cho tng khuch i dng JFET nh trn hnh 3- 51. Hy xc nh R v Rs- Vi

Ku = l,

Ic = 12mA; Up= -3V; = 40kQ.

Bi tp 3-64. Cho bkhuch i gm hai tng nh trn hnh 3-52. Hy xc nh in p ra u. Vi I dss = 8mA; p = -4,5V.

ra

101

Bi tp 3-65. Cho b khuch i gm hai tng nh trn hnh 3-53. Hyxc nh h s khuch i K. VI Iss = 6mA, Up = -3V, = 150.

( ^ Bi tp 3-66. Hy xc nh Rv v R ca b khuch i cho n hnh 3-53.

( l ^ Bi tp 3-67. Cho tng khuch i Cascode nh trn hnh 3-54. Hy xc nh h s khuch i K v in p ra u. Vi Uy = lOmV, , = , = = 200

102

( l ^ Bi tp 3-68. Cho tng khuch i Darlington nh trn hnh 3-55. Hyxc nh K.

( ^ Bi tp 3-69. Cho tng khuch i Darlington nh trn hnh 3-56. Hy xc nh in p ra . Vi Pi = 160; P2 = 200.

ra

(1^ Bi tp 3-70. Cho mch in ng JFET nh trn hnh 3-57. Hy xc nh dng in I viIoss = 6mA;Up = -3V.

R2 k i

Hnh 3-57

103

Bi tp 3-71. Hy xc nh dng in I cho mch in trn hnh 3-58 vi p = 100.

4,3kR,

-

Chng 4

MCH KHUCH I CNG SUTm w

4.1. TM TT PHN L THUYT

Nhim v ca tng khuch i cng sut l a ra ti mt cng sut ln theo yu cu, c th t vi chc mW n hng trm hay hng ngn w . H s khuch i cng sut ng vai tr quan trng, cn h s khuch i in p ch l th yu.

- Tng cng sut c th lm vic cc ch khc nhau; ch A, AB, B hay ch c , nhng khuch i cc tn hiu iu ha thng s dng hn c l ch A v AB (hay cn gi l ch B|).

- y l tng khuch i tn hiu ln nn buc phi lm vic on cong ca c tuyn transistor nn s gy mo phi tuyn.

- Tng cng sut c th mc theo s ofn hay s y ko, c th dng ngun cp in n cc hay ngun i xng c im gia trung ha.

- Hiu sut ca tng cng sut quyt nh hiu sut ca my khuch i; vic nng cao hiu sut ngoi ngha tit kim nng lng cn lm gim cng sut tiu tn trn v transistor di dng nhit.

- Cc tng khuch i cng sut c phn ra: tng cfn, tng y ko, tng c bin p ra, tng khng bin p ra...

* Tng cig su t m c n ti in tr (hnh 4-1)

Hnh 4-1. Tng cng sut mc n ti in tr

khuch i cc dao ng iu ha tng ch lm vic ch A, trong transistor lm vic trong c hai na chu k tn hiu.

105

Cng sut ra p = = Is 2 = -Hsm-" 2 2 2R

Trong U, = U c B = |v I = I

p_. , = H - k = i . = i l , Eramax 2 2 2 ^ 4 *

Cng sut tiu th t ngun

Po = Ico E

Hiu sut cc i khi p -> p,ra max

n = i = -|. 100% = 25% 4 I E

Thc t hiu sut cn thp hn.

in tr ti xoay chiu ti u c xc nh:

C t.h . 2 K

u im: tn hiu t b mo

Nhc im: cng sut ra nh, hiu sut thp.

* Tng cng sut mc n c bin p ra (hnh 4-2)Bin p ra c chc nng ngn mt chiu, dn tn hiu xoay chiu ra ti

R ng thcri phi hp tr khng.

iu kin phi hp tr khng

Rra = R( = R(_ wTrong n = h s bin p;

W2

R - in ra ca tng khuch i;

R, - in tr ti;R, - in tr ti quy v s cp bin p.

T suy ra n =i

R.R.

106

Nu bin p ra l l tng th in tr ti xoay chiu mch ra

u_ UI Ira - co

a) Hinh 4-2. Tng cng sut mc n, c bin p ra

- Cng sut ra cc i

2 2

b)

ramax- Cng sut tiu th t ngun:

Po = U,.I^ = I,E- Hiu sut cc i:

=1 E.I

Po 2 E.I^100% = 50%

Trong thc t bin p lun c tn hao v tn ti in p d Udu nn hiu sut cn nh hn.

Khi lm vic vi ti ti u bin in p cc i Uca, bng 2E Y ti mang tnh in khng nn xut hin sc in ng cm ng trong cun s cp bin p.

* Tng cng sut m c theo s y ko c bin p ra (hnh 4-3)

BA l bin p o pha;BA l bin p ra.Tng c th lm vic ch A hay ch B nhng thng l ch

AB vi dng tnh I,.o (1 0 100) ^A.

107

.

ruyL

r"TT~V i :u -v v -^ ^

+E

B T,AI Ba2

a)

Hnh 4-3. S cng sut (a) v c tuyn ra (b)

in tr ti ca mi transistor (1/2 cun s cp l W| vng) c xc nh,

w, w.

R, = n'.R, Suy ra n = R n = -^R

- Cng sut ra cc i mt nhnh

p _ il r ; _ I.. UcB. _ I.n Eni max 2 2 2

Dng in trung bnh trong mt chu k ca mt nhnh (1 transistor)

1 I ...I n

Dng tiu th t ngun E (c hai nhnh); = 2.n

- Cng sut tiu th t ngun E:

Po = I .E = -I,E n

Hiu sut cc i ca tngp F.

Imax

71

= -100%=78,5% 4

108

Thc t bin p c tn hao v cEm < E nn hiu sut thp hn.Cng sut tiu tn trn colect ca mt transistor di dng nhit.

P _ p I I

2

Suy ra p = -^ P wO,4Pcmax _2 r;iniaxnKt lun:

- ch B hay AB khi Uy = 0 tng khng tiu th nng lng.- Ngn mch ti v h mch ti khi c tn hiu vo u rt nguy him

cho transistor.* Tg cng sut y ko m c ni tip khng hin p ra (hnh 4-4)

1R,

R. c,

11 1

I I 'u.JL R.: ; R,

Hnh 4-4

mc ti trc tip khng qua bin p phi dng ngun i xng E c im gia trung ho, cc cc + v -E khng c ni vi v my. Transistor T|, Tt l hai nhnh ca tng cng sut, dng hai transistor khc loi dn in, u mc theo s ti emit nn khng khuch i c in p. Tng T, l tng kch cng sut v khuch i in p, ti xoay chiu l Rj; D| v D, lm nhim v to thin p v n nh nhit cho T| v T,.

Tng thng lm vic ch AB. Cc tnh ton ca tng ny ging nh xt trn.

* Tng cng sut m c theo s y ko ng t phn cch c>Trong trng hp khng c ngun i xng m ch c ngun n cc,

mun mc ti trc tip, khng qua bin p th phi dng t phn cch Cp mc ni tip vi ti.

T Cp c hai chc nng: ngn thnh phn dng mt chiu qua R, v lm ngun th cp cho T2 khi T| tt. T Cp s phng, np qua T|, T-, v R,.

109

Tng Tj v cc linh kin hp thnh ging nh s dng ngun i xng.

4.2. PHN BI TP C LI GII

(1^ Bi tp 4-1. Cho mch khuch i cng sut nh hnh 4-5 a

Bit: E =12V

Rc = 20Q

R, = 2kQ

U be = 0,5V; p = 50

Dng in vo c bin Iv = I b = 5mA.

a) Xc nh im lm vic tnh 0 v ng ti mt chiu, xoay chiu.

b) Xc nh dng Ic ng vi ly = 5mA.

Bi gii

a) Dng tnh Ibo c xc nh

12-0 ,5

Hnh 4-5a

= 5,75mA

I,(mA) R=R~1 \ 287,5

....V /V/ ..... x, ^6,25 U(V)Hnh 4-5b

E -U e,o _____R, 2.10'

Dng tnh colect

Icx) = PIbo = 50.5,75 = 287,5mA

- in ap U(^ = 12-IqqRc =12 - 287,5. lOMO = 12 - 5,75 = 6,25V

im lm vic tnh o c to o (6.25V; 287,5mA).

- v ng ti mt chiu v xoay G hiu ( y = R_ = Rc) cn xc nh thm mt im na ngoi im o . Bit phng trnh ng ti U,, = E-IcR c

Cho Ic = 0 u = UcE = E = 12V. Ni im o vi im 12V trn trc honh ta c ng ti mt chiu.

Trong trng hp ny v R = R. nn ng ti mt chiu v xoay chiu trng vi nhau.

110

b) Khi dng in vo Ig bin thin 5mA th dng in ra s bin thin

a) Hiu sut ca tng.

b) Cng sut tiu tn trn colect ca transistor.

Bi gii

a) xc nh hiu sut, cn xc nh cng sut ra ti v cng sut tiu th._ ("250

- Cng sut ra p = ^ R = .20 = 0,625W2 2

- Cng sut tiu th t ngun

Po = E.I, = 12.287,5.10' = 3,45W

Hiu sut T = ^ ^ 1 0 0 % = 18,1 %' 3,45

b) Cng sut tiu tn trn colect transistor

Pc = Po - Pra = 3,45 - 0,625 = 2,825W

(Q ) Bi tp 4-3. lp li bi 4-1.

Nu gim bin dng tn hiu vo cn 3mA

Hy xc nh:

a) Cng sut ra.

b) Hiu sut ca tng.

c) Cng sut tiu tn trn colect.

d) Cho nhn xt.

Bi gii

a) Xc nh cng sut ra

- Dng in ra = Ig .p = 3.50 = 150mA15010"^y

- Cng sut ra = -^ R . = ^ 20 = 0,225W

111

- Cng sut tiu th, khng i

P= L,,n= 12. 287,5 .10 ' = 3 ,45w

b) liu su ca tn

p . . 0 225n = 100% = - - - 100% - 6,52%

K 3,45

c) Cng su tiu tn trn colect P(.

= p - = 3,45 - 0,225 = 3,225W

d) Nhn xt:

- Cns sut tiu th t ngun l c nh, khng ph thuc vo mc lnhiu vo, vl tng lm vic ch A.

- Bin tn hiu vo gim th hiu sut gim v cng sut tiu tn P(~ tng ln.

(1 ^ Bi tp 4-4. Cho mch khuch i cng sut c bin p ra nh hnh 4-2.

Bit dng in tnh l|i = 3iiA; = 20; H = 12V; Un|,,) = 0.6V, bin dnt din vo |j, 4mA.

St p trn R,v : R,.; = 1V; R, = 8Q; n = = 4 .

a) Xc nh in tr R| v R,.

b) Xc nh dim lrn vic tnh, ng ti mt chiu v xoay chiu.

c) Xc dinh dng , v in p u ,.

Bi gii

a) Xc nh tr s in tr R| v R,

- u, = u,,; + U,,o = 1.0 + 0,6 = 1 ,6V

U,, - I,.R, R, - = % - V - so n' l , 4I 4 .5 .1 0 '

- U |^ | = ( I , + I q ) R = E - U 2

l, + I, 51., 5.5.10

1 2

b) Xc nh im lm vic tnh

Nu coi bin p l l tng th C E O = E = 12V

Ico lo 20.50 = lOOmATo im lm vic tnh o (12V; lOOmA)

in tr ti quy v s cp bin p

R, = n-R, = 4 l8 = 128n

T im trn trc honh c in p Uc0 = 12V cng thm mt on in p bng = 100.10'll28 = 12,8 V, c im B k ng thng qua B v o ta c ng ti xoay chiu.

T th xc nh, ng vi dng In, bin thin 4mA.U c e . = 22V

U c E . i n = U a . = 3 V

Icmax= 180 mA

Icmin = 2,0 tA.

Bin dng cc i I180-2 = 89mA

Bin in p ra cc i

IU CEmax ^CEmn

2 2 -3 = 9,5V

8- 250BTKTINT-A 113

( ^ B tp 4-5. lp li bi 4-4

a) Xc nh cng sut ra ti.b) Xc nh cng sut tiu th.c) Xc nh hiu sut ca tng.d) Cng sut tiu tn trn transistor.

B gii

a) in p hiu dng trn cun s cp bin p:

TI I 79 ' I = - ^ = = 6,74 V

72 2y2 i S- Gi tr hiu ng in p bn th cp bin p tc l trn ti R,:

U ,= U = A 7 4 = 1.685V

- Cng sut ra ti:

p = ^ = l ^ = 0 , 3 5 5 W R. 8

b) Cng sut tiu th t ngun:

Po = E.I, = 12V.100.10' = 1,2Wc) Hiu sut ca tng:

p ___ 0 355T1 = -^100% = = 29,58%Po 1 ,2

d) Cng sut tiu tn n v transistor Pc

Pc = Po - Pra = 1,2 - 0,355 = 0,845W

Bi tp 4-6. lp li bi 4-4. Nhng gim in tr ti xung cn 4 0 . Hy xc nh cng sut ra, hiu sut v cng sut tiu tn Pc-

Bi gii

a) Nu R = 4Q, th R, = n .R, = 4 .4 = 64Q, to im B trn trc honh by gi l 12V + 100.10164 = 18,4V. T th (hnh 4-6) ng vi Ib = 4mA so vi Igo ta xc nh c

8 -250BTKTOINT - B

U., = U ce=18V

. = c h m = U, = 3V

Icmin = 2mA Q _ = 1 8 0 m A

Bin in p ra khng mo

n - UcB.a.-UcB.n_ 18-3CEm 2 2

- in p hiu dng bn s cp bin p

. = ^ = ^ = 5,32Vn/2 >/2

- in p hiu dng bn th cp bin p

- Cng sut ra

1 5 32U ,= U ^ .- = ^ = 1,33V

' ""*4 4

P , = ^ = !4 )! = o,442W " R 4

Cng sut tiu th

Po = I,.E = 100.10M 2 = 1,2Wp 0 442

b) Hiu sut TI = ^ .100% = ^^^.100% = 36,83% Po 1 ,2c) Cng sut tiu tn

Pc = Po-p = 1,2-0,442 = 0,758 w Kt lun: Khi in tr ti gim cng sut ra tng ln.

( 1 ^ Bi tp 4-7. Cho tng khuch i cng sut (KCS) mc cfn lm vic ch A nh hnh 4-7.

Hy xc nh cng sut ra (P) hiu sut ca tng (i) vi bin dng20

baz Ib = lOmA; p = 25; Ic(B) = ^ = = OOOmA20

Ecc = ce(A) = 20V ; Ube = 0,7 V

115

" E 20V

o

20Q

+ IcT(Si)

a)

Hnh 4-7

Bi gii

Ta im Q c xc nh theo phcttig trnh cmg ti mt chiu (R_)

R, 1.10'

= .Ibo = 25.19,3mA = 0,48 A

Uceo = Ecc - IcoRc = 20 - 0,48. 20 = 10,4V

- To hai im A v B trn trc honh v trc tung tofng ng s l: 20V v lOOOmA.

- Bin dng ra (dng colect) s l:

Icm = Ibm- = lOmA.25 = 250mA

p = 2 5 0 ]0 2 20 = 0,625wm 2 ^ 2

P o = E c c - I c o = 2 0 . 0 , 4 8 = 9 , 6 W

^ = ^ 1 0 0 % = ^ ^ 1 0 0 = 6 , 5 %

Po 9 ,6

( l ^ Bi tp 4-8. Cho tng khuch i cng sut ghp bin p nh hn 4-8.

116

u.

Hy xc nh cng sut ra trn ti.E lO V

R.l

w,5 ^R. 8f

X

a)

l _ = 2 2 5 m A

AIc

400-

2oa-

l . =25mA 1001-,

T A )

4m A

12mA

lOmA8m A

6m A

4mA2mA-j^ ^ H-- ^

5 10 15 p o 25 U J V )

Uc.,=18.3V

b)

Hnh 4-8

w 3Vi cc s liu cho thm: Ibo = 6mA; I( = 4mA; n = = = 3

W2 1

Bi gii

Dng ng ti mt chiu R_ nh trn hnh 4-8b, ta c c: = lOV

I,,= 140mA

in tr ti phn nh t th cp v s cp ca bin p l: R, = n .R, = 3 \s = 720

Bin dng colect c xc nh:

I =- = i =i39mA R , 72

To im B trn trc tung s l:

rc..x = Ico + I c . = 140+ 139 = 279mA Ni im Q v B ta s c ng ti xoay chiu R. ct trc honh ti

im c ,, = 20V l im A .Trn hnh 4-8b vi bin dng = 4mA ng ti R ct cc ng

c tuyn ra tomg ng vi = I| + Ibn, = 6 + 4 = lOmA

v Ibi = Ib - b = 6 - 4 = 2mAr

Khi ta c cc gi tr in p u v Ic tng ng

117

Ui=l,7V Ui = 25mA u _ = 18,3V u , = 255mA

nh trn hnh v 4-8b.Cng sut ra s l:

p _ ^ cemax cemn ^ciTiax cmin8

( 1 8 , 3 - 1 , 7 ) ( 2 5 5 . 1 Q - ^ - 2 5 . 1 0 - ^ ) p

8

(15^ Bi tp 4-9. Cho tng khuch i cng sut nh hnh 4-8 da trn kt qu bi tp 4-8.Hy xc nh Pq; Pc v t|.

Bi gii

p = = 10V.140.10' = 1,4 wp = Po - p= 1,4 - 0,477 = 0,92 w

p __ 0 47711 = - ^ 100% = 100% = 34,1%

Po( i Bi tp 4-10. Cho b KCS lm vic ch B vi = 20V, ^ R, = 16Q, E = 30V.

Hy xc nh Pq, Pr "n.

Bi gii

Vi bin in p ra 20V v ti 16Q ta ti c bin dng ti s l:

I,m = U = ^ = ^ = U 5 A .lo

Dng tiu th trung bnh l:

I .b = % = - = r ( U 5 ) = 0,796A71 71

Cng sut tiu th t ngun cung cp s l

Po = Ecc.I,b = 30.0,796 = 23,9 w Cng sut ra ti l

U i (20 f " 2R. 2.16

118

Hiu sut ca tng l:

TI = ^ 100% = 100% = 52,3%Po 23,9

(l6^ Bi tp 4-11. Cho b KCS dng transistor lm vic ch B mc y ko nh hnh 4-9 (gi thit transistor l tng). Hy xc nh cng sut tiu tn Pc trn mi -ansistor, p, Po v . Vi Uv hiu dng (rms) l 12V = vnro-

Bi gii

Bin in p vo l:

u., = >/2.U_ = n/2.12V = 17Vvm vrmsVi tng KCS l tng ta coing bng (khng c tn hao trn tip gip baz-emit).

Cng sut ra s !:

17p ^ = 36,125W2R. 2.4ra

Bin dng ti l;

U _ 17I. = l.n,= - ^ = J = 4.25A

Dng trung bnh c tnh

71Cng sut tiu th t ngun cung cp l:

p,b = = 25.2,71 = 67,75W

Cng sut tiu tn trn mi transistor l

67,75-36,125 = 15,8W

119

Hiu sut ] l:

^ 1 0 0 % = 1 0 0 % = 5 3 , 3 %

tb 67,75

162) Bi tp 4-12. Cho tng KCS lm vic ch A nh hnh 4-10. Hy xc nh dng tnh I(.o v cng sut tiu th t ngun cung cp Po-

Bi gii

E E cc ________ cc______" R _+R _ R ,+ R ,+ R ,

+E,, 24V

E=24W

~ X r r ^R , t 'jR ,8 n

I - .

Hnh 4-11

U:

E 24= = = 1,454A

2R^+R^ 2.8+ 0,5

( y R _ = R,; R - = R , + R ,)

Po = = 24.1,454 = 34,896 w

(16^ Bi tp 4-13. Cho tng KCS nK hnh 4-11. Hy xc nh h s bin p n vi p = 9 w?

Bi gii

= 9W , t ta xc nh c bin in p ra trn ti , 2R,

U,.=VP.2R, = 7 ^ = 12 V

Vi gii thit r, = (bin p c cun s cp l tng) nn bin in p ra phn nh v s cp u ng bng u 0 v bng E.

, = U = E,, = 24V

u . 12

120

( ^ Bi tp 4-14. Qio tng KCS lm vic ch A nh hnh 4-11 (xenn bi tp 4-13). Hy xc nh cng sut tiu tn trn colectQa transistor T.

Bi gii

Ico =E E 24

R. + R_ R',+0 n^R, 2\8

Po = E,Ao = 24.0,75 = 18W

Vy p, = Po - p = 18 - 9 = 9 W

( l ^ Bi tp 4-15. Cho mch khuch i cng sut nh hnh 4-12. Bit hai transistor l l tng = 0, I = o, E = 20V. Bin p ra l l tng,h s bin p n = 2.

R, = 8Q; R2= lOOQ.

a) Xc nh tr s in tr R| tng lm vic ch AB

Y T /\ \ rVI U beo = 0 . 4 V .

Hinh 4-12b) Tnh dng in cc i qua transistor.c) Tnh hiu sut ca tng.d) Cng sut tiu tn trn colect.

Bi gii

a) Thin p BEO c xc nh theo biu thc:

Suy ra R, = - R, = - 00 = 4,9kfU ^ 0 4BEO ^Bin p l tng nn UgEo = E = 20V v dng tnh 10 = ( )m Ab) Dng colect cc i

E E 20 , = T = , - - = = 1,25AR , n".R, 2-.8

121

- Cng sut ra cc i

__ CEm cmax __ 20.1,25 = 12,5W

- Cng sut tiu th t ngun

P=E.L = E .- .I = 20 .1,25 = ]5,92W " 71 3,14

c) Hiu sut cc i ca tng:

Tln,.,x = .100% = - ^ . 1 0 0 % = 78,5% p 15,92d) Cng sut tiu tn:

= p - = 15,92 - 12,5 = 3,42 w

Bi tp 4-16. lp li bi 4-15. Nu gi thit tng lm vic ch A vi thin p U g E o = 1,2V. Hy xc nh in tr R|.

Bi gii

ch A c ha transistor T| v T2 lm vic ng thi, thin p t voT, vT^l 1,2V

R.U b e o = 1 , 2 V =

R, +Rj.E

Suy ra R, = l,566kQUbeo 1,2

(1^ Bi tp 4-17. Cho tng khuch i cng sut nh hnh 4-13. Hai transistor T| v T2 c

= 0,5V; I, = ImA. Tng lm vic ch AB. Cng sut , ra p, = 25 W; in tr ti R, = 8Q.

a) Xc nh dng in cc i qua transistor.

b) in p ngun cn thit.

1 2 2

a) T biu thc = R, (ong l bin dng in ra mt nhiih)

Bi gii

Suy ra I, , - I,2P '2.25

= 2,5A

b) T biu thc (U, l bin in p ra cc i)2R,

in p U,,, = u,. + U,, = ^P.2R, + ,, = V2 5 .2.8 + 0,5 = 20,5V

in p ngun E = 2(P,,.2R, + ) = 2 (7 2 5 .2.8 + 0,5 ) = 41V

E 20,5V.

(1^ Bi tp 4-18. Qio mch khuch i cng sut nh hnh 4-14. Bit R, = 8Q;

p, = 5 w. H s khuch i T, v % p = 50 UI = 0,5 V; Tng lm vic ch B| c Bg()| U BE02 = 0,2V

a) Tnh dng cc i qua transistor.

b ) in p U ceo-

c) in p ngun cung cp.

d) Cng sut ra cc i.

Bi gii

a) T biu thc p, , = -^ .R ,

Suy ra dng cc i =V R. 8

b) in p Uceo = /2P,,,R. + = ^ /5 I + 0,5 = 9,44V

c) in p ngun cung cp

E = 2 ( ^ 2 1 ^ + ) = 2 + 0 ,5 ) = 18,88 V

123

d) Cng sut ra cc i ---- L- = 5Wrama* 2 .R 2.8

(1^ Bi tp 4-19. lp li bi 4-18. Nu bit dng colect ca transistor T,

Icx)3 == 1.5Iboi = l ,5Ig02 (Ibom Ibo-> dng tnh baz ca transistor T v Tj)a) Hy xc nh in tr Rj v in tr nhit R,.

b) Xc nh cng sut tiu th.

c) Xc nh hiu sut ca tng.

Bi gii

- Dng tnh qua transistor Tj

leo, = 1,5I = 1 , 5 ^ = 1 ,3 - ! ^ = 33,5mAPmin

a) in tr Rj c xc nh

E= = = =281,8

Ic o , Ic o . 2 I , 2.33,5.10'2 T I O T ' ' e i n -3*co

- in tr nhit Rt

2 UR = .- ....E. = = 1 ,9 Q 1 2 f

Ico3 33,5.10

b) Cng sut tiu th t ngun

p. = -l ,..U c B 0 = r ^ l . ' 8 .9 ,4 4 = 7,095WK J ,1 4

c) Hiu sut cc i ca tng

2.0,2

p 4 99 X] = l i = -Z1Z_. 100% = 70,33%Po 7,095

( l ^ Bi tp 4-20. bi lp li bi 4-18. Nu thay bng hai it ging nhau mc ni tip thun chiu. Gi s dng qua Tj bng 1,2 Igoi, Ibo->- Hy chn hai it; dng qua T 3 , in tr Rj.

124

a) Xc nh dng qua Tj

Ia>5 = 1 .2 1 , , = 1 . 2 - ! ^ = 1 . 2 ^ = 2 6 . 8 m A

b) in tr R.,;

U F. Q 44R = - 5 - = _ Z l!!_ = 352,20

I, I, 26,8.10-

c) in tr thun ca hai it

= f e o i K|BEil. = _ _ M _ = 14,920C03

Bi gii

Ieo3 26,8.10

Chn hai it hon ton ging nhau c in tr thun14 Q2

R d . = R d 2 = - ^ = 7 , 4 6 0 .

( l ^ Bi tp 4-21. Cho mch khuch i cng sut nh hnh 4 - 1 3 . Bit

E = 2 5 V

R, = 4 Q

Gi s in p vo c gi tr hiu dng l lOV.

a) Tnh cng sut ra ti.

b) Tnh cng sut tiu th t ngun.

c) Tnh hiu sut ca tng.

d) Tnh cng sut tiu tn trn mi transistor.

Bi gii

a) Gi tr bin ca in p vo

U . = '/2 U ., = ^ y 2 .I0 = 1 4 ,lV

T| v T, mc theo s ti emit nn in p ra coi nh bng in p vo

U . < P ) = 1 4 , 1 V

Cng sut ra ti

125

C ^ ( H ) 1 ,2 4 ,8 5 W 2R, 2.4

Bin dng in ti

I = ^ = = 3 525A

b) Xc nh cng sut tiu th t ngun

- Dng trung bnh I,b trong c chu k

Cng sut tiu th

Po = I,b.E = 2,245.25 = 56,125 w

c) Hiu sut ca tng

p 24 85ri = ^ 100% = 100% = 44,17%

p 56,25

d) Cng sut tiu tn trn colect ca mi transistor

p _p.-p _ 56.125-24.85 _ 2 2

( l ^ Bi tp 422. Mt tng khuch di khi cha c hi tip m c h s khuch i in p k(dB) = 40dB, v in p vo Uy = lOOmV. tng n nh v gim mo, a vo mch hi tip m in p c h s

hi tip k(,t = .^ 200

a) Tnh h s khuch i khi c hi tip.

b) in p ra khi cha c hi tip v khi c hi tip.

c) in p hi tip.

Bi gii

) H s khuch i khi cha c hi tip kjB = 40 B. Suy ra K = 100

- H s khuch i khi c hi tip m:

126

= 100 ^

' + K-K. , + iooJ-200

b) in p ra khi cha c hi tip

u = K.v = 66,6.100.10-' = 6,66Vc) in p hi tip

u = K -U = 10 = 0,05V = 50mV

Bi tp 4-23. Mt tng khuch i cng sut sau khi lp rp o c tno phi tuyn l 6%.

gim mo phi tuyn xung cn 1 % ngi ta mc vo mt mch hi tip m.

a) Hy tnh su hi tip.

b) Tnh h s khuch i khi c hi tip. Nu gi thit khi cha c hi p v = 0,5 V th u = lOV.

Bi gii

a) Tnh su hi tip g

T biu tc y ' = ----------- , frong . mo phi tuyh khi cha c hi tip

y: mo phi tuyn sau khi c hi tip m._____ Y 6

Suy ra su hi tip g = 1 + KK,, = -L = = 6y' 1

K.Kh, = 6-l = 5

5

bit K = ^ = = 20 ln0,5

K = = 0,25 20

b) H s khuch i khi c hi tip

127

K' = K1 + K.K

= ^ = 3,33ht 6

( ^ Bi tp 4-24. Cho mch khuch i dng J-FET c hi tip nh hnh 4-15.Bit: R, = 120kQ

R2 = 30kQ

R3 = 20kQ

Rd = 20kf

HdncaPET g = 5 mA

a) Tnh h s khuch i khi cha c hi tip m.

b) Tnh su hi tip g v K,,.

c) Tnh h s khuch i khi c hi tip K. ,

Bi gii

y l mch hi tip m, khi cha tnh n hi tip {h R| v R,)

a) H s khuch i

K = g,.R. trong R_ l ti xoay chiu

Ri+Rp 20 + 20

K = 5. l0l l0" = 50

b) H s hi tip Kh,

30R| +Rj (120+30) 5

1 su hi tip g = 1 + K.Kh, = 1+ 50 - = 11

c) H s khuch i khi c hi tip m

KK' =l + K.Kht

. # = 4,54511

128

( l ^ Bi tp 4-25. gim mo phi tuyn cho tng khuch i cng sut t 5% xung cn 1% ngi ta a vo mch hi tip m qua phn p Rj, R,. Bit khi cha c hi tip K = 20dB.H yxcnhtrs R ,vR 2. -----

Bi gii

- K(dB) = 20dB. Suy ra K = 10

a) Xc nh h s hi tip K|,1

Bit y' =1 + K.K,,

Hnh 4-16

Kh.=1

/y

\- 1

I - - > '

_ 4K I y / " 1 0 U ; " 1 0

b) in tr phn p hi tip

Kh. =R - 4

R, + R 2 10

gii ra; R = 1,5R2 Nu chn = 20kQ th R| = 30kQ. ---------------------- - ---'I ---

( 1 ^ Bi tp 4-26. Mch khuch i thut ton khng o nh hnh 4-17.

Bit h s khuch i ca bn thn b KTT Ko = 10; Rn = IMQ; R, = 20k2

a)Tnh h s hi tipKh,.

b) Tinh h s khuch i khi c hi tip.

Bi gii

a) H s hi tip

K . = ^ = = 4 = 0.02ht RN 1.10" 50

b) H s khuch i khi c hi tip m K1f)4

K' = -----^ - = ----- --------- = 49,751 + K.K l + 10^0,02

9- 250BTKTNT-A 129

Chng 5

B KHUCH I THUT TONm

5.1. TM TT PHN L THUYT

B khuch i thut ton (KTT) l b khuch i mt chiu, c hai u vo mt u ra, h s khuch i rt ln, in p ra t l vi hiu in p vo, in tr vo rt ln v in tr ra rt nh.

Hin nay hu nh ch s dng b KTT di dng IC. Hnh 5-la l k hiu b KTT.

U. N

p p -Ea) K hiu KTT

ra

Hnh 5-1

Theo nh ngha u = Ko(Up- u,,) = KoU,

trong : = Up - Un l sai lch in p u vo;

Kq l h s khuch i ca bn thn b KTT.

Nu N = 0 th = Kq Up in p ra ng pha vi in p vo v ca p c gi l ca vo thun, k hiu +.

Nu Up = 0 th = - KqUn , in p ra lun ngc vi in p vo v ca N c gi l ca o v k hiu l (-).

130 9- 250BTKTOJNT-B

Cc tham s c bn ca ICKTT

Tham s L tng Thc- Tr khng vo Zv 00 Trm kQ

- Tr khng ra z 0 Trm Q

- H s khuch i Kq 00 lOUO^- Dng in vo Ip, Ifg 0 Trm nA

* H s nn ng pha

Nu Un = Up = # 0 (U . gi l in p ng pha), theo l thuytu = 0 , nhng trong thc t khc khng.

u = Kc . - K,. gi l h s khuch i ng pha.

H s nn ng pha (CMRR) l t s gia h s khuch i ca IC TT l trng Ko v h s khuch i ng pha

CMRR = ^ ; CMRR(dB) = 201g ^ , dB.Kp K ,

CMRR vo khong (70 100) dB.

* c tuyn truyn t (hnh 5-lb) l quan h gia u v Uv = Up - Un u v Uv ch tuyn tnh trong mt khong hp, ngoi phm vi in p ra khng thay i v gi l in p bo ho. Khi cha c mch hi tip m bn ngoi, IC TT lm vic ch bo ho E.

* Lch khng v h ch khng

Nu thng s tnh hai ca vo p v N khng hon ton cn bng Ip v Z|, t Zn th khi Un = Up = 0 vn tn ti in p mt chiu Uo no Uo = IpZp-lN Zn

in p ny c khuch i v u ra tn ti in p u ,0 0 gi lin p lch khng, bi vy phi c bin php u lun bng 0 khi Uy = 0 gi l mch b lch khng.

V nguyn l, mch b lch khng c thc hin bng cch b vo u vo mt in p mt chiu c tr s ng bng Uq v c cc tnh ngc vi Q. Mch ny c th thc hin bng cch a in p vo ca p hay N hoc IC c sn cc chn mc mch b lch khng.

* M ach khuch ai o

131

in p cn khuch i c a n ca o N, cn Rn v R| l hai

in tr hi tip mch ngoi (hnh 5-2).

i vi IC TT l tng, h s khuch i khi c hi tip c xc nh

K = ^ v in p ra u , = - ^ .Uv R, " R,

Du (-) y c ngha l in p ra v vo lun ngc pha.

b)

Hnh 5-2. Cc sd khuch i thut ton c bn

* B khuch i khng o

in p cn khuch i c a vo ca thun p (hnh 5-2b).

H s khuch i in p c xc nh theo biu thc:

U,. = ( l + ^ ) U ,

Nu gia Uy v in p ca p c mch phn p in tr th Up xc nh

theo Uy qua mch phn p .

* M ch cng v tr (hnh 5-3)

Mch cng l mch thc hin hm u = A(U|+2+...+U).

Trong U|, u , l cc in p vo.

Tu theo s c th l mch cng o hay cng khng o.

132

a) b)Hinh 5-3. Mch cng (a) v tr (b)

Hnh 5-3a l mch cng o.

in p ra c xc nh.

K| Kj

Mch tr (hnh 5-3b)

C th gii mch in theo nhiu phng php khc nhau, nhng thun tin hon c l s dng phng php xp chng.

U = ( l + ^ ) U p - ^ U ,K, K,

= ( i + ^ )R| Rj + Rp

* Mch vi phn v tch phn (hnh 5-4)

Hnh 5-4a l mch vi phn dng IC TT

R RR,

R

a) b)

Hnh 5-4. Mch vi phn (a) v tch phn (b)

133

in p ra mch vi phn (hnh 5-4a)

U = - R C ^ = - x ^

R.

Hinh 5-5

dt dt

Hnh 5-4b l mch tch phn dng IC TT

in p u ra mch tch phn (hnh 5-4b)

u = - ^ '|u.(t)dt=-!-|u.dtK U 0 T 0

Trong X = RC gi l hng s thi gian.

5.2. PHN BI TP C LI GII

@ Bi tp 5-1. Cho mch KTT nh hnh 5-5

R , = lOkn

R N = 500kQ

R p = lOkn

E= 12V

Vit biu thc U,,.

Tnh nu Uy = 0,2V v cho nhn xt.

Bi gii

a)U,. = - ^ U .

b)U = . ^ U , = . ^ . 0,2 = - l 0V.K| lU

in p ra -lOV ln hcfn E = -12V nn tn hiu ra nm trong vng tuyn tih, khng b mo.

( l ^ Bi tp 5-2. Hy tnh ton v thit k mch khuch i thut ton vi cc yu cu sau;

a) in p ra ngc pha vi in p vo.

b) Nu U, = 0,5V th u = 15V.in tr vo = 20k2.

134

V in p ra ngc pha vi in p vo nn y l mch khuch i o, s mch in nh hnh 5-4. *

H s khuch i: *

Bi gii

u . 0,5

Mt khc

K = - ^ = 30 suy ra Rn = 30R, R,

V R, chnh l in tr vo R, = R, = 20kQ

Suy ra Rn = 20kn .30 = 600kQ.

179) Bi tp 5-3. Cho mch KTT nh hnh 5-6a

rra

R2^vl--/S/^

-R

1

a)b)

Hinh 5-6

Bit R, = 20kQ

Rn = 780k2

R, = 20ka

E = 15V

a) Vit biu thc xc nh Ura-

b) Tnh ,, nu bit u , = 0,30V.

135

a) V in tr vo ca p rt ln nn c th coi nh khng c dng qua/ \ / \

R2 nninp, = Up,U= 1 + u , = 1 + R, / R, J

Bi gii

/ \

U p =R , J

pR , >\ 1 /

b)TnhU: U = ( 1 + ^ ) . 0 , 3 = 1 2 V

u = 12V < E = 15V, tn hiu khng b mo.

Bi tp 5-4. Cho mch in nh hnh 5-6b BitRn = 500k2 R, = 20kQ

= 20kn

Rj = lo mR4 = 3 0 m

= 400mV

= SOOmV

a) Xc nh biu thc u.b) Tnh tr s ca u.

Bi gii

*a) C th gii mch in trn theo cc phng php khc nhau, nhng tin hn c l dng phng php xp chng.

- Nu ch tc ng =

- Nu ch tc ng R, -> u =

R + 1 R3//R4

R1 y

R ,+ (R J /R ,)

R2//R.

.u

R ,+ (R J /R ,)u

u = u, + u,= 11 + _ R.

R 3/ /R , R 3//R , v , + - ---- *_ .Uv.' R ,+ (R ,//R .)^2 +CR3//R4)

R3 //R4 = 7,5kfR3+R, 10 + 30

136

R2//R4 =20.30

R ,+ R , 20 + 30= 12k2

b) Tnh tr s u: Thay s vo

U = ( l . ^ ) 20 20 + 7,5 10 + 12

= 9,906V

(18^ Bi tp 5.5. Cho mch in nh hnh 5-7 y l mch g?Vit biu thc tnh u^.Tnh u nu bit:U, =0,15V 2= IV

= 500R2, R , = 20kQ

R 2 = 30k2, R p = 20kf

Bi gii

ra

Hnh 5-7

a) y l mch tr, thc hin thut ton u = AUy2 thit lp biu thc u, tin hon c l gii theo phng php xpchng- Nu ch tc ng ngun tn hiu u^, y l mch khuch i o

RVI

Nu ch tc ng tn hiu u^2 l mch khuch i thunR

.UR, Rj + Rp

V2

in p ra: = u , , , + 2 =

b) Thay s vo

R I

RRs+Rp

UR

V2R ,

-.uVI

. 1,0 - .0,15 = 6,65 V 20 20 + 30 20

(1^ Bi tp 5-6. Thit k v tnh ton mch khuch i thut ton thc hin thut ton sau:

137

Y = 2a -4b *Trong : Y l in p u ra;

a v b l hai in p vo;4 v 2 l h s.

Bi gai

thc hin thut ton trn phi dng mch tr. S nh hnh 5-7.

a) Xc nh biu thc in p ra

Y = ( l+ : ^ )R R

R, R, + R_ R,

So snh biu thc v * suy ra

(1+4^)R

= 2

RR,

L = 4

RR

N 4. Suy ra Rn = 4R

T>

Thay = 4 vo: R.

RR R

^ = 2 - (1 + 4)------ -R,+R^

= 2

R . + R .

Nh vy thc hin thut ton trn phi chn:

Rn = 4R| v R = 1,5 Rp.Nu R, = 20k n th Rn = 80ka

Nu Rp = 20kQ th R2 = 30kn.

(18^ Bi tp 5-7. Cho mch khuch i thut ton nh hnh 5-8

a) Vit biu thc tnh h s khuch i K.

138

b) Tnh tr s u nu bit: R, = lOkQ, R2 = 200k2

R, = 20kQ, R4= 15k2 Rs= 150kO,E= 15V

U, = 0,15V.

Cho nhn xt

Hnh 5-8

Bi gii

a) y c th coi nh hai tng khuch i mc k tip nhau, tng IC| c h s khuch i l K| tng IC| c h s khuch i l K.

H s khuch i K c xc nh;

UK =

U= K , K ,

Trong ; K| =(1 + )R,

R R R,= Suyra:K = K,.K3 = ( l + 3 ( - ^ )R R, R,

R, K

b) Tnh Ura

1 +200^

2 0 j

1 5 0

1 5

.0,15=-16,5V

139

Nhn xt: V in p ngun -E = -15V trong khi = -16,5V, nhu v y in p ra b xn nh, nn b mo. in p ra tuyn tnh phi gim hay gim h s khuch i K.

(1^ Bi tp 5-8. Xc nh phm vi iu chnh in p ra trong mch hnh 5-9 Bit: R| = 10k2

Rn = 250ka R p = (0 -2 0 )k a

U v = 0,2V

Bi gii

- Vit biu thc in p ra Hnh 5-9

u = -R. .U.

R,+Rp

- in p ra s cc tiu khi chit p Rp = 02

u = - | ^ u . = 0 , 2 = - 5 V

- in p ra s cc i khi Rp = 20k

R.u . = -

R.+R..

250,u = . _ ^ . 0,2 = - 1 ,66V10 + 20

Nh vy in p ra s bin bin thin trong khong t -5V n -1,66Vkhi iu chnh chit p R p .

(1^ Bi tp 5-9. Cho mch KTT nh hnh 5-10.

Bit: R , = 15kO

R = 250kQ R3 = 20k2

R 4 = 470k0

E = 9 V

U, = 25mV

ICTTl l tng

140

a) Vit biu thc h s khuch i K.b) Tnh tr s u v cho nhn xt.

Bi gii

Dng in ti nt N

I| = I j + I n v I n = 0 nn I, = I2

Trong d l | =R

U v - U , U^-U^ Suy ra: - ^ M

R

R R

V N l im t o, nn N = Up = 0

v cui cng = . Suy ra = - Uy *R , R j R ,

Ti nt M: It +I 4 - Ij = 0

Um , U . - U m H R. R. R

R, R4

Thay gi tr t * vo v gii ra ta c.

1 1 1U = . R ,

R. ^

/ \ 1 1 1 1

1^2U.

H s khuch i

K =uu R

RI 1 1

Tnh in p ra:

U = - ^ .4 7 0 '15

1 1 +250 20 470

25.10' l i v

in p ra u,, = 11V > +E = 9V. Tn hiu ra b xn nh.

141

( l ^ Bi tp 5-10. Cho mch cng o nh hnh 5.11

BitR, =20k2 R= 25ka

R, = 30k2 ; = 500kf

U ,=0 ,1V

U, = 0,2V

3 = 0,3V

a) Vit biu thc u.b) Tnh u.

u, .---V\Ar U.

Ru ,

+E

-E

Hnh 5-11

U

Bi gii

a) y l mch cng vi ba in p vo U|, u, v u,; gii mch theo phcng php xp chng:

R

u=u,+u,+u,,,= - ^ . u , + ^ . 3 + ^ . U , R. ' R, R,

500 , , 500 , , 500 , ,U, +^ U, +^ U,

20 25

b) Thay s vo

^500

3025U,+20U,+ U,

' 30

u = -500

.0,1 + 20.0,2 + .0,3 20 30

= -l l ,5V

Bi tp 5-11. Cho mch in nh hnh 5-12

a) Vit biu thc h s khuch i K.

b) Xc nh tr s nu bit:

142

Uv = 0,5VR, = 20kQ; R2 = 20kQ; Rj = 30kQ R4 = 250kQ; R, = lOkQ

Hnh 5-12

Bi gii

a) H s khuch i K = Ki-K,trong K| = 1 y l mch lp in p u = ,

K .= 1 + v K. =IRs ;

11

. R, >\ 5 yb) in p ra

u,. = ( 1 + ^ ) -U. = (1 + .0,5 = 5,2VV _ _ 10 20 + 30= u + --- =TT--U. = U + -----)~r / r , + R 3 ' 10 2(

(1^ Bi tp 5.12. Cho mch in nh hnh 5-13Bit Rn = 500k2R, =25k2 E = 1 2 Vin p bo ho lOVXc nh in p vo cc i m in

p ra vn trong phm vi tuyn tnh.Xc nh u vi cc gi tr u = 0 ;

u = 0,4V. Hnh 5-13

Bi gii

H s khuch ai;

143

K = = . 5 5 = . 2 0 .R. 25

U

in p vo nh - nh Vp.p

vp-p = H ^ = ^ = 0 ,5 VK 20

u = i u = - ^ . U , = -20UR 25

Tnh tr s u,v .ov ov

+0,4V -8V

-0,4V +8V

Bi tp 5-13. Cho mch khuch i nh hnh 5-14

U v R .vv\/w

Hinh 5-14

a) Vit biu thc I v u 2

b) Tnh tr s u| v bit:

U. = 0,5 V

144

R, = Ra = 20k f; R3 = 3 0 k a ; R4 = 25kQ

R3 = 500kQ ; Rg = 500kQ; R7 = 25kQ.

Bi gii

a) u, = K,.K2 , ; trong K, l h s khuch i ca IC,

K2 l h s khuch i ca IC2

., = - ^R u = + M l . u

R.R4

b) Thay s ta c:

U. = .0,5 = lOVR..R 20.25

U, = . ( u M , . 0 , 5 = . , 0 . 5 V2 0 ' 25

{1^ Bi tp 5-14. Cho mch khuch i thut ton nh hnh 5-15.

Hnh 5-15

a) Vit biu thc u.b) Xc nh tr s nu bit:R, = 20k2 ; R2 = 500ka , R3 = 25kf

R4 = 2 0 k a ; Rs = 3 0 k a ; = 60ka

, = 0 , 2 V ; 2 = 0,3V.

10- 250BTKTINT.A 145

a) y l b khuch i c hai tng IC| v IC2 c hai in p vo.

Trc ht xc nh in p Ural

Bi gii

,= ,.

y chnh l in p a vo ca o ca ICj. Gii mch in ICj:

1 +i l l R3 . U,-

R