Prob2EExpBTHieu

Bi s 2: Cc dng ghp c bn ca mch khuych i tn hiu nh

Bi Trung Hiu. Lp: DD02KSTN: www.buitrunghieu.edu.tf

Bi th nghim s 2: CC DNG C BN CA MCH KHUCH I TN HIU NH I. Mch khuch i ghp E chung:

1. Phn cc DC: a. Tnh ton phn cc:

Xc nh dng tnh EQI : Th t ti cc C l 6.5V,

dng tnh 12 6.5

5.51000

CC CCQ

C

V VI mAR = = = , suy

ra dng emiter: 1 131

5.5 5.542130

FEEQ CQ

FE

hI I mA mAh+= = = . p

dng Kirchhoft 2 v phn p, ta s c:

2 1 22

1 2 1 2

5.9ccE D BQV R R RV V I R k

R R R R+ = +

+ +,

chn gi tr 2 5.6R k= . T :

( )

( )1 2

1

1 2

//

5.081//

1

CCD

EQ

EFE

V R R VRI mA

R RR

h

= =

++

, in p

tnh

( ) 13012 1 390 5.081 4.96130 1CEQ CC C CQ E EQ

V V R I R I k m V = + = + = +

b. Phn cc Maxswing: Khi K ng, ta c: 1AC CR R k= = , 1390DC C ER R R= + = ,

2 1 22

1 2 1 2

5.506ccE D BQmaxswingV R R RV V I R k

R R R R+ = + =

+ +chn gi tr 2 5.6R k= .

c. Cc gi tr o: Dng Fluke45, ta s o c cc gi tr: CEQV , EEQE

VIR

=

Tnh ton phn cc

EQI (mA) CEQV (V) Tnh ton o c Tnh ton o c

5.081 5.4835 4.96 4.6378

Ta o c Vc=6.5165(V) 6.5(V), phn cc cho BJT xp x gi tr maxswing. 1. Ch AC:

a.S tng ng tn hiu nh khi K ng: 25.61.4 130 9175.081

T

EQ

mV mhie hfeI m

= =

Cc gi tr tm c bng l thuyt:

( )// 1 //1

Ein i b E

CZ R R hie hfe Rhfe

= + + + + , 1out cZ R k= =

Ti tn s f=1kHz, ta tm c: 1.77inZ k=

li p: out out bVin b in

V V iAV i V

= =

( )( )( )

25.660

38.1 18.2Vj j

Aj j

+

+ +

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Ti tn s cho, 60VA . T , li cng sut: 2

2 1.7760 63721

out out inp

in in out

P V Z kAP V Z k

= = = = .

R rng chng ngc pha nhau. iu gi thch cho du - xut hin trc cng thc li p. Thc t o c:

Cc thng s ca mch ghp E chung Gi tr in p nh-nh Tng tr Tn s ct li

Vi(mV) Vout(V) Zin(kOhm) Zout(kOhm) LT o LT o LT o LT o L

f (Hz) Hf (kHz) vA (db) pA (db)

50 50 3 2.6 1.77 2 1 0.987 138.69 135 35.6 76.1 S khc nhau gia l thuyt tnh ton v thc t do tnh ton l tng ho cc gi tr t k sinh, khng tnh n nh hng ca nhit , nhiu, v khi chn cc gi tr tnh ton cho hfe, Cbe, Cbc khng tht s chnh xc nh trong bn Datasheet ca Transitor (Q2SD468-Hitachi). V d nh ly cc gi tr hFE, Cbe khng chnh xc ti gi tr dng collector Ic tng ng(trong bi ly gi tr tiu chun).

Gi s ta chnh li cc thng s nh sau: hFE=100, Tf =85Mhz, ' 30b cC pF= , lp tc ta c ngay:

' 374b eC pF= , khi , bng m hnh m phng Transitor Q2SD468(Cc thng s c dng trong Pspice nh sau: .model Q2sd468 NPN(Is=4.344f Xti=3 Eg=1.11 Vaf=100 Bf=100 Ise=4.365f Ne=1.288 Ikf=.7482 Nk=.429 Xtb=1.5 Var=100 Br=13.13 Isc=4.344f Nc=1 Ikr=.1613 Cjc=30p Mjc=.3333 Vjc=.3905 Fc=.5 Cje=374p Mje=.3333 Vje=.65 Tr=10n Tf=934.7p Itf=1 Xtf=0 Vtf=10 Af=0)) v bng m hnh tng ng ca n (hie=712W, g=0.14), ta c dng sng ra so snh nh sau:

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R rng lc ny, cc gi tr m phng, o c rt gn nhau. Tn s ct cao c s chnh lch gia m hnh tng ng, BJT m phng do m hnh tng ng cha k n cc s b chnh khc. Gi tr o ngoi thc t li b chi phi bi s quan st ca ngi thc hin, m dao ng k khi s dng di tn cao th li b nhiu nn rt kh quan st, tuy nhin, gi tr xp x khong t 130kHz n 160kHz c th chp nhn c. b.S tng ng tn hiu nh khi K m:


( )( )( )// 1in i b EZ R R hie hfe R= + + + 1out cZ R k= =

Ti tn s f=1kHz, ta tm c: 4.945inZ k=

li p:

out out bV

in b in

V V iAV i V

= =

( )2

9VjA

j

+

Ti tn s cho, 2VA . T , li cng sut: 2

2 4.9452 19.781

out out inp

in in out

P V Z kAP V Z k

= = = = .

Thc t o c: Gi tr in p nh-nh Tng tr li

Vi(mV) Vout(mV) Zin(kOhm) Zout(kOhm) LT o LT o LT o LT o v

A (db) pA (db)

38 38 74 68 4.945 4.9 1 0.973 5.1 23.9 Nu dng li cc thng s chuyn i, ta s c Vout=67mV(nh-nh). iu ny cng khng nh s ng n ca vic chn li cc thng s ca BJT. T y v say, khi tnh l thuyt, ta ly cc gi tr mi ny.

II. Mch khuch i ghp B chung:

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1. Phn cc DC: a. Tnh ton phn cc: Dng cc nh l chia dng, p, ta c ngay:

2'

1 2

2.85ccCCV RV V

R R= =

+,

' 2.85 0.61 5.184271

3901011

CC BEEQ

bE

V VI mAR Rhfe

= = =++

+

,

( )100

12 1 390 5.18 4.85100 1

CEQ CC C CQ E EQV V R I R I

k m V

= +

= + = +

b. Cc gi tr o: Tnh ton phn cc


5.18 5.4 4.85 4.6373 Nhn xt: Cc gi tr o v tnh ton xp x nhau.

1. Ch AC:

a.S tng ng tn hiu nh khi K ng: 25.61.4 75.18

T

EQ

mV mhibI m

= =


( )1 //1

bin e b

RZ R hib hfe Chfe

= + + + + ,

1out cZ R k= = Ti tn s f=1kHz, ta tm c:

0.44inZ k=


V V iAV i V

= =

2.5VA

T , li cng sut: 2

2 0.442.5 2.751

out out inp

in in out

P V Z kAP V Z k

= = = = .

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Trong m phng, vi cc gi tr cho BJT nh ni trn, sng Vout gp 2.5ln sng Vin nn khi i t l biu din trn my Osillocope, chng trng nhau(cng pha). Thc t o c:

Cc thng s ca mch ghp B chung Gi tr in p nh-nh Tng tr Tn s ct(M phng) li

Vi(mV) Vout(mV) Zin(kOhm) Zout(kOhm) LT o LT o LT o LT o L

f (Hz) Hf (MHz) vA (db) pA (db)

100 100 250 240 0.44 0.44 1 0.9 11.13 7.6 8.8 Tn s ct cao b gim so vi Tf do c hiu ng Miller.

III. Mch khuch i ghp C chung: 1. Phn cc DC:

a. Tnh ton phn cc: Dng cc nh l chia dng, p, ta c ngay:

2'

1 2

2.85ccCCV RV V

R R= =

+, '

2.85 0.615.18

4271390

1011

CC BEEQ

bE

V VI mAR Rhfe

= = =++

+

,

12 390 5.18 9.98CEQ CC E EQV V R I

m V= = =

b. Cc gi tr o:

Tnh ton phn cc


5.18 5.505 9.98 9.853 Nhn xt: Cc gi tr o v tnh ton xp x nhau.

1. Ch AC:

a.S tng ng tn hiu nh khi K ng: 25.61.4 100 6925.18

T

EQ

mV mhie hfeI m

= =


( ) ( )// 1 //1

bin i i b b

CZ R ntC nt R hie hfe Rhfe

= + + + ,

( )// 1 0.41 1

b iout E i

R RZ R hib nt hfe C khfe hfe

= + + + = + +

Ti tn s f=1kHz, ta tm c: '4.889 3.889inin

Z k Z k= = (b Ri) 378outZ =


V V iAV i V

= = Suy ra 0.78VA

T , li cng sut: 2

2 4.8890.78 7.440.4

out out inp

in in out

P V Z kAP V Z k

= = = = .

Thc t o c: Cc thng s ca mch ghp C chung

Gi tr in p nh-nh Tng tr Tn s ct(M phng) li Vi(V) Vout(V) Zin(kOhm) Zout(Ohm)

LT o LT o LT o LT o Lf (Hz) Hf (MHz) vA (ln) pA (ln)

2.3 2.3 1.8 2.3 4.858 4.889 400 378 1.58 8.28 1 12.9 http://www.khvt.com



Tn s ct cao b gim so vi Tf do c hiu ng Miller. Ta c th kt lun php o Vout(hay Vin) khng tnai lch n hn 20%

Biu din li theo tn s:

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