1Chng 6: Op-Amp

Chng 6-2

NOI DUNG

Gii thiu Op-Amp Mch Op-Amp c bn Mch Op-Amp nang cao

Chng 6-3

6.1 Gii thieu Op-Amp

Ten goi Cau tao Ky hieu ac tnh ac tuyen Mo hnh Op-Amp ly tng Mach so sanh Mot so Op-Amp thc te

Chng 6-4

Ten goi Op-Amp

Vi mch khuch i thut ton (Operational Amplifier) k hiu l OpAmp u tin c dng ni v cc mch khuch i c kh nng thay i theo mch ghp ni bn ngoi thc hin cc php bin i ton hc nh cng tr, bin i t l, vi tch phn... trong cc my tnh tng t.

Nh s pht trin ca cng ngh bn dn, Op-Amp ngy cngtr nn tin cy, kch thc nh, n nh nhit, v vy, ngy nay opamp c s dng nh l thnh phn c bn ca cc ng dng khuch i, bin i tn hiu, cc b lc tch cc, to hm v chuyn i.

Chng 6-5

Cau tao Op-Amp

C s ca vi mch khuch i thut ton l cc tng khuch i vi sai.Cc vi mch khuch i thut ton bao gm ba phn:9 Khuch i vi sai:Dng khuch i tn hiu vo, c c im l khuch i nhiu thp,tr khng vo cao, thng u ra vi sai.9 Khuch i in p:To ra h s khuch i in p cao, thng u ra n cc.9 Khuch i u ra:Dng vi tn hiu ra, cho php kh nng ti dng ln, tr khng ra thp, c cc mch chng ngn mch v hn ch dng in.

Chng 6-6

Ky hieu Op-Amp

Vi+: ng vo khng o Vo: ng ra Vi-: ng vo o +/-VS cung cp ngun

Chng 6-7

ac tnh Op-Amp

Mt b vi mch khuch i thut ton khuch i vi sai in p vd= v1 v2 gia 2 tn hiu vo. H s khuch i in p hmch c tnh theo cng thc:

AOL=V0/Vd vd: ng vo vi sai AOL li p vng h Rd in tr vo R0 in tr ra

BW=f1-f2 :bandwidth

20log ( )vdVC

ACMRR dBA

= =11 cdo d

d

VV VA CMRR V = +

Chng 6-8

ac tuyen Op-Amp

+/- Vs ngng in th ng vo (rt b vi trm micro vol)

+/-V0max gi tr cc i ng raVi < -Vs: vng bo ha mVi > -Vs: vng bo ha dng-Vs< Vi

Chng 6-9

Mo hnh Op-Amp ly tng

0

V

i

o

ARR

trnh tn hiu ra bo ha khi tn hiu vo qunh , khng dng cch khuch i vng h khi khng cn thit.

tn hiu vo ln v tn hiu ra khng b bo ho ( khng b xn) khuch i hi tip ( cho 1 phn tn hiu ra vo li ng vo)

Chng 6-10

Mach so sanh dung Op-Amp

So snh khng o:

y in th chun Vref > 0V t ng vo (-)y in th so snh Ei a vo ng vo (+)y Khi Ei > Vref th V0 = +Vsaty Khi Ei < Vref th V0 = -Vsat

Chng 6-11

Mach so sanh dung Op-Amp (tt)

Mch so snh o:

in th chun Vref > 0V t ng vo (+) in th so snh Ei a vo ng vo (-) Khi Ei > Vref th V0 = -Vsat Khi Ei < Vref th V0 = +Vsat

Chng 6-12

Mach so sanh dung Op-Amp (tt)

Mch khuch i c hi tip:Lc ny do vin so snh vi tn hiu ng vo v+ l in th trn mch phn p R4-R2, nn theo s bin thin gia hai mc in p ca vout, mch hi tip cngc hai ngng so snh l VH v VL.

Chng 6-13

Mot so Op-Amp thong dung

Chng 6-14

Mot so Op-Amp thong dung (tt)

LM381: low noise dual amp., audio.Voltage gain= 112dB; BW = 75KHz; Rin= 100K; Rout= 150.

LM380: audio power amp.Voltage gain= 34dB; BW= 100KHz; out-put power = 2W

MC1553: Video amp.Voltage gain= 52dB; BW=20MHz

LM703: RF/IF amp.

Chng 6-15

Op-Amp n

Chng 6-16

Op-Amp kep

Chng 6-17

Op-Amp 4

Chng 6-18

6.2 Mach Op-Amp c ban

Mach khuech ai khong ao Mach khuech ai ao Mach khuech ai tong Mach khuech ai vi sai Mach tch phan Mach vi phan Mach tao ham mu Mach tao ham logarith

Chng 6-19

Mach khuech ai khong ao

2 2

1 1

1 1oo ii

VR RV V AR V R

= + = = +

Nhn xt:Ng ra Vo cng pha vi ng vo Vi c gi l ng vo khng o. R2 ng vai tr hi tip m tng khuch i AV.Khi R2 =0, ta c: A=1 => Vo =Vi hoc R1= ta cng c A=1 v Vo= Vi . Lc ny mch c gi l mch voltage follower thng c dng lm mch m (buffer) v c tng tr vo ln v tng tr ra nh nh mch cc thu chung BJT.

Chng 6-20

Mach khuech ai ao

0

2 1

0 2

1

0 0 0 i

i

i i V Vv v R R

V RV R

+

+

= = == =

Nhn xt: Vo v Vi s lch pha 180 (nn c gi l mch khuch i o vng vo ( - ) c gi l ng vo o).R2 ng vai tr mch hi tip m. R2 cng ln (hi tip m cng nh) khuch i ca mch cng ln. Mch c kh nng khuch i in p DC ln AC

Chng 6-21

Mach khuech ai cong

01 2

1 2

1 2

1 2

0 ... 0

...

n

n f

no f

n

V VV Vv vR R R R

VV VV RR R R

+ = = + + + + =

= + + +

9Nhn xt :Nu R1=R2==Rn= R th

Nu Rf=R th Vo l tng ca tt c cc ng vo Vi (Tng ny phi nh hn Vsat ca op-amp)

( )1 2 ...fo nRV V V VR= + + +

Chng 6-22

Mach khuech ai cong (tt)

1 2

1 2

...1 1 1 1...

1 2

n

f no

N

n

VV VR R R RVR

R R R

+ + + = + + +

9Nhn xt

Nu R1=R2==Rn th

Gi tr ng ra Vo bng tng cc ng vo khi v ch khi Rf=0 hoc RN=.

( )1 21 ...fo nN

RV V V V

R = + + + +

Chng 6-23

Mach khuech ai vi sai

2 12 1 1

1g f fog

R R RV V V

R R R R = + +

Nhn xt:

Nu th

Nu Rg=Rf =R1=R2 th Vo =V2-V11 2f gR R

R R= ( )2

1

1foR

V V VR

=

Chng 6-24

Mach tch phan

( ) ( ) ( )0

1 1 0t

o i i oV V t dt V t dt V tRC RC = = + =

Nhn xt: Gi tr ng ra Vo t l vi tch phn gi tr ng vo.

Tn s ct:

Nn mch tch phn ch hot ng ng mt dy tn s nht nh.Ngoi ra chng ra cn c th ly tch phn ca mt tng.

1cf RC=

Chng 6-25

Mach vi phan

0i

oi o

v vdvV RCdv V dtC

dt R

+ = = ==

Nhn xt:Gi tr in p ng ra Vo t l vi vi phn in p vo .

Tn s ct:

Mch vi phn hot trong trong mt dy tn s nht nh, ti c tuyn bin -tn s: c dc 20dB/decade.

1cf RC=

( )oi

V fV

=

Chng 6-26

Mach tao ham mu

: in p ri trn hai u diode : dng ngc bo ha

1

. . .

. .

i

i

VV V

o s

Vs

V R I e k e

k R I e

= =

=

V

sI

Chng 6-27

Mach tao ham logarith

: in p ri trn hai u diode : dng ngc bo ha

( ) ( )ln ln lnio i ss

VV V V V V RII R

= = +

V

sI

Chng 6-28

6.3 Mach Op-Amp nang cao

Mach chuyen oi dong sang ap Mach chuyen oi ap sang dong Mach khuech ai dong Mach khuech ai instrumentation

Chng 6-29

Mach chuyen oi dong sang ap

Cn gi l b khuch i bin i in tr, c u vo l iiv u ra l: vo =Aii trong : A l li ca mch.Xem hnh trn ta c: ii +(vo -0)/R=0 hay vo = -Rii

Chng 6-30

Mach chuyen oi ap sang dong

)3(2,1

)2(0)1(

RV

RVIi

IiiZVVVA

io

odi

ioL

======

===

+

Chng 6-31

Mach khuech ai dong

+==

1

21RR

ii

Ai

oi

Chng 6-32

Mach khuech ai instrumentation

Vo = A(v2 v1)A = A1 .A2 = (1+2R3/RG).(R2/R1)

Chng 6-33

Mach khuech ai instrumentation (tt)

vo = -R2v3 /R1 +(1+R2)v2 /R1

Chng 6-34

TOM TAT

Gii thiu Op-Amp Mch Op-Amp c bn Mch Op-Amp nang cao