ch 3 - feedback.ppt

7/25/2019 CH 3 - Feedback.ppt

1/54

CHAPTER 3FEEDBACKAMPLIFIERS

EMT 212/4 Analog Electronc II


2/54

!"tlne

1# Intro$"cton to Fee$%ac&

2# Fee$%ac& A'(l)er Po*t+e , -egat+e

3# A$+antage*/D*a$+antage* o. -egat+e

Fee$%ac&4# Ba*c Fee$%ac& Conce(t

# Cla**)caton o. A'(l)er*

0# Sere* S"nt Con)g"raton

# S"nt Sere* Con)g"raton

# Sere* Sere* Con)g"raton

5# S"nt S"nt Con)g"raton


3/54

Intro$"cton to Fee$%ac&

Fee$%ac& * "*e$ n +rt"all6 all a'(l)er *6*te'#

In+ente$ n 152 %6 Harol$ Blac& engneer n7e*tern Electrc Co'(an6

'eto$* to *ta%l8e te gan o. a'(l)er .or"*e n tele(one re(eater*#

In .ee$%ac& *6*te'9 a *gnal tat * (ro(ortonalto te o"t("t * .e$ %ac& to te n("t an$co'%ne$ :t te n("t *gnal to (ro$"ce a$e*re$ *6*te' re*(on*e#

Ho:e+er9 "nntentonal an$ "n$e*re$ *6*te're*(on*e 'a6 %e (ro$"ce$#


4/54

Fee$%ac& A'(l)er

Feedback* a tecn;"e :ere a (ro(ortono. te o"t("t o. a *6*te'


5/54

Po*t+e Fee$%ac&

Po*t+e .ee$%ac& * te (roce** :en teo"t("t * addedto te n("t9 a'(l)e$agan9 an$ t* (roce** contn"e*#

Po*t+e .ee$%ac& * "*e$ n te $e*gn o.o*cllator an$ oter a((lcaton#


6/54

Po*t+e Fee$%ac&

E?a'(le In a PA *6*te'

get .ee$%ac& :en 6o" ("t te'cro(one n .ront o. a *(ea&er an$ te*o"n$ get* "ncontrolla%l6 lo"$


7/54

-egat+e Fee$%ac&

-egat+e .ee$%ac& * :en te o"t("t **"%tracte$.ro' te n("t#

Te "*e o. negat+e .ee$%ac& re$"ce* tegan# Part o. te o"t("t *gnal * ta&en %ac&to te n("t :t a negat+e *gn#


8/54

-egat+e Fee$%ac&

E?a'(le S(ee$ control

I. te car *tart* to *(ee$ "( a%o+e te$e*re$ *et(ont *(ee$9 negat+e.ee$%ac& ca"*e* te trottle to clo*e9tere%6 re$"cng *(ee$ *'larl69 . te

car *lo:*9 negat+e .ee$%ac& act* too(en te trottle


9/54

Fee$%ac& A'(l)er

Conce(t

Ba*c *tr"ct"re o. a *ngle loo( .ee$%ac& a'(l)er


10/54

A$+antage* o. -egat+eFee$%ac&1# an Sen*t+t6 +araton* n gan *

re$"ce$#

2# Ban$:$t E?ten*on larger tan tat o.

%a*c a'(l)e$#3# -o*e Sen*t+t6 'a6 ncrea*e S- rato#

4# Re$"cton o. -onlnear D*torton

# Control o. I'(e$ance Le+el* n("t an$o"t("t '(e$ance* can %e ncrea*e$ or$ecrea*e$#


11/54

D*a$+antage* o. -egat+eFee$%ac&

1# Crc"t an o+erall a'(l)er gan *re$"ce$ co'(are$ to tat o. %a*ca'(l)er#

2# Sta%lt6 (o**%lt6 tat .ee$%ac&crc"t :ll %eco'e "n*ta%le an$o*cllate at g .re;"ence*#


12/54

Ba*c Fee$%ac& Conce(t

Ba*c con)g"raton o. a .ee$%ac& a'(l)er


13/54

Ba*c Fee$%ac& Conce(t

Te o"t("t *gnal *>

:ere A * te a'(l)caton .actor

Fee$%ac& *gnal *

:ere * te .ee$%ac& tran*.er ."ncton At *"''ng no$e>

Clo*e$loo( tran*.er ."ncton or gan *

.

AS=oS

oS=fbS

fbi SS =S

A

A

S

S

i

o

+==

1fA

11 =>>

A

Athen fAA


14/54

Cla**)caton o. A'(l)er*

Cla**.6 a'(l)er* nto 4 %a*c categore*%a*e$ on ter n("t


15/54

Fee$%ac& Con)g"raton

Series:

connectngconnectng

tete

.ee$%ac&.ee$%ac&

*gnal*gnaln *ere* :tn *ere* :t

tete

n("t *gnaln("t *gnal

+oltage#+oltage#Shunt:

connectngte.ee$%ac&*gnaln *"nt


16/54

Sere* S"nt Con)g"raton

vv

vvf

A

AA

+=1


17/54


.Lo RR

si RR >>

fbi V=VVvv

v

i

ovf

A

A

V

VA

+==1

:ere + * clo*e$loo( +oltage tran*.er


18/54


!r

In("t c"rrent

Rif:t .ee$%ac&

A**"'e an$ ?a((le$ to o"t("tter'nal#

!r

In("t c"rrent

Rof:t .ee$%ac&

Input Resistance, Rif Output Resistance, Rof

)( VAVVV vvfbi +=+=V

)1( vv

i

AVV

+=

)1( vvi

i

i

i

AR

V

R

VI

+==

)1( vvii

iif AR

I

VR +==

0=+=+ xvfb VVVV xvVV =

o

vvx

o

vxi

RAV

RVAVI )1( +==

)1( vv

o

x

xof

A

R

I

VR

+==


19/54

Sere* n("t connecton ncrea*e n("t re**tance a+o$ loa$ng e@ect* on te n("t *gnal *o"rce#

S"nt o"t("t connecton $ecrea*e te o"t("tre**tance a+o$ loa$ng e@ect* on te o"t("t *gnal

:en o"t("t loa$ * connecte$#

E;"+alent crc"t o. *"nt *ere* .ee$%ac& crc"t or+oltage a'(l)er



20/54

For $eal nonn+ertngo(a'( a'(l)er

Fee$%ac& tran*.er."ncton


-onn+ertng o(a'( * an e?a'(le o.te *ere**"nt con)g"raton#

+==

1

21R

R

V

VA

i

ovf

+

=

1

21

1

R

R


21/54


E;"+alent crc"t )1(/

1

11

1

221

1

21

1

21

1

vii

i

i

i

if

voi

v

v

v

v

i

ovf

ofb

fbi

ARRV

V

I

VR

R

R

VAVV

RR

RVV

A

A

RR

R

A

A

V

VA

VRR

RV

VV

+===

+

+=

++=

+=

+

+==

+

==

V

VAVvo


22/54


E?a'(le>

Calc"late te .ee$%ac& a'(l)er gan o.te crc"t %elo: .or o(a'( gan9

A19 R12 G an$ R21# &G#

Sol"ton> A+. 5#555 or 1


23/54


Ba*c e'tter.ollo:er an$ *o"rce.ollo:ercrc"t are e?a'(le* o. $*cretecrc"t*ere**"nt .ee$%ac& to(ologe*#

vi* te n("t

*gnalerror *gnal *%a*ee'tter/gate

*o"rce +oltage#.ee$%ac& +oltage o"t("t +oltage.ee$%ac&

tran*.er ."ncton9


24/54


S'all*gnal +oltage gan>

!(enloo( +oltage gan>

Clo*e$loo( n("t

re**tance>

!"t("t re**tance>

e

E

e

E

Em

Em

i

ovf

r

R

r

R

Rgr

Rgr

V

VA

+=

++

+

==11

1

1

e

EEmv

r

RRg

rA =

+=

1

++=++= EmEmif Rgr

rRrgrR

11)1(

Em

E

m

Eof

Rgr

R

rg

rRR

++

=+

=

11

)1(


25/54

S"nt Sere*Con)g"raton

ii

iif

A

AA

+=1


26/54

S"nt Sere*Con)g"raton Ba*c c"rrent a'(l)er :t n("t re**tance9 R

an$ an o(enloo( c"rrent gan9 A#

C"rrent IE * te $@erence %et:een n("t *gnal

c"rrent an$ .ee$%ac& c"rrent#

Fee$%ac& crc"t *a'(le* te o"t("t c"rrent (ro+$e .ee$%ac& *gnal n *"nt :t *gnalc"rrent#

Increa*e n o"t("t c"rrent ncrea*e .ee$%ac&c"rrent $ecrea*e error c"rrent#

S'aller error c"rrent *'all o"t("t c"rrent *ta%l8e o"t("t *gnal#


27/54

S"nt Sere*Con)g"raton. si RR

IAI io=.ee$%ac& c"rrent *>oiIIfb =

In("t *gnal c"rrent>

fbi II += I

ii

i

i

oif

A

A

I

IA

+

==

1

ten IIi

:ere * clo*e$loo( c"rrent tran*.er .


28/54

S"nt Sere*

Con)g"raton

!r

In("t c"rrent

Rif:t .ee$%ac&

Input Resistance, Rif

)( IAIII iifbi +=+=I

)1( ii

i

AII

+=

)1( ii

iiii

A

RIRIV

+==

)1(ii

i

i

iif

A

R

I

VR

+

==

A**"'e I an$ I?a((le$

to o"t("t ter'nal#

Rof:t .ee$%ac&

Output Resistance, Rof

[ ]oiixx

oxiixx

oixx

xi

xifb

RAIVRIAIV

RIAIV

II

IIII

)1()(

)(

0

+==

==

=+=+

( )iio

x

x

of

ARI

VR

+== 1


29/54

S"nt Sere* Con)g"raton

S"nt n("t connecton $ecrea*e n("t re**tance a+o$ loa$ng e@ect* on te n("t *gnal c"rrent *o"rce#

Sere* o"t("t connecton ncrea*e te o"t("t re**tance a+o$ loa$ng e@ect* on te o"t("t *gnal $"e to loa$

connecte$ to te a'(l)er o"t("t#

E;"+alent crc"t o. *"nt *ere* .ee$%ac& crc"t or+oltage a'(l)er


30/54


!(a'( c"rrent a'(l)er *"nt*ere*con)g"raton#

I .ro' e;"+alent *o"rce o. Ian$ R*#I* neglg%le an$

R*R

a**"'e 1+rt"all6

gro"n$

C"rrent I1>

!"t("t c"rrent>

I$eal c"rrent gan>

fbii II == 'I

FiFfbo RIRI ==V

1/RVo=1I

+=+=

1

1 1R

RIII FifboI

+== 11

R

R

IA F

ii

oI


31/54


A * o(enloo(c"rrent gan

an$ A**"'e 1* +rt"all6

gro"n$>

I1c"rrent>

!"t("t c"rrent

fbifbi IIII = 'I

)( fbii IIA == IAI io

FfbRI=oV

Clo*e$loo( c"rrent gan>

==

11

1R

RI

R

V Ffb

oI

+=+=

1

1R

RIIII FfbfbfboI

+

+==

1

1

1

R

R

A

A

I

I

F

i

i

i

oifA


32/54


Co''on%a*e crc"t * e?a'(le o.$*crete *"nt*ere* con)g"raton#

A'(l)er gan> Clo*e$loo(c"rrent gan>

RL

Io

Ii

I

RLIo

Ii

I

Ifb

== iAI/oIi

i

i

oif

A

A

I

IA

+

=

+

==

11


33/54


Co''on%a*e crc"t :t REan$ RC

RC

Io

RE

Ii

V-V+

RC

Io

RE

Ii

i

E

i

m

E

m

i

oif

AR

r

A

rgR

r

rg

I

IA

+

+

=+

+

==

11


34/54

Sere* Sere*Con)g"raton

gg

g

gfA

AA

+=

1


35/54

Sere* Sere*Con)g"ratonTe .ee$%ac& *a'(le* a (orton o. te

o"t("t c"rrent an$ con+ert* t to a +oltage +oltagetoc"rrent a'(l)er#

Te crc"t con**t o. a %a*c a'(l)er tatcon+ert* te error +oltage to an o"t("tc"rrent :t a gan .actor9 Agan$ tat a* an

n("t re**tance9 R#

Te .ee$%ac& crc"t *a'(le* te o"t("tc"rrent an$ (ro$"ce* a .ee$%ac& +oltage9 .%9

:c * n *ere* :t te n("t +oltage9 #


36/54

Sere* Sere*Con)g"ratonA**"'e te o"t("t * a *ort crc"t9 teo"t("t c"rrent>

VAI go=.ee$%ac& +oltage *>

ozIVfb =In("t *gnal +oltage

fbi VV += V

gz

g

i

ogf

A

A

V

IA

+==1

:ere 8 * a re**tance .ee$%ac& tran*.e


37/54


A**"'e I an$ I?a((le$

to o"t("t ter'nal#

Rof:t .ee$%ac&


[ ]ogzxx

oxzgxx

ogxx

xz

xzfb

RAIV

RIAIV

RIAIV

II

IIII

)1(

)(

)(

0

+==

==

=+=+

( )gzox

x

of

ARI

VR +== 1

!r

In("t c"rrent

Rif:t .ee$%ac&


)( VAVVV gzfbi +=+=V

)1( gz

i

AVV

+=

)1( gzi

i

i

i

AR

V

R

VI

+==

)1( gzi

i

iif AR

I

VR +==


38/54

Sere* Sere*Con)g"raton Sere* n("t connecton ncrea*e n("t re**tance

Sere* o"t("t connecton ncrea*e te o"t("tre**tance

E;"+alent crc"t o. *ere* *ere* .ee$%ac& crc"t or+oltage a'(l)er


39/54


Te *ere* o"t("tconnecton *a'(le*te o"t("t c"rrent

.ee$%ac& +oltage * a."ncton o. o"t("tc"rrent#

A**"'e $eal o(a'(

crc"t an$ neglecttran**tor %a*ec"rrent>

Ei

ogf

Eofbi

RV

IA

RIV

1==

==V


40/54


A**"'e IEICan$R

( )

( ) Egmgm

i

ogf

Eoigmo

Eoifbi

gmbm

E

fb

o

RArg

Arg

V

IA

RIVArgI

RIVVVV

VArgIrgR

VI

+==

=

==

===

1


41/54



42/54


Em

LC

Cm

i

ogf

Emfbi

Emfb

LC

Cmo

Rg

r

RR

Rg

V

IA

Rgr

VVVV

RVg

r

VV

RR

RVgI

++

+

==

++=+=

+=

+=

11

11

)(


43/54

S"nt S"nt Con)g"raton

zz

zzf

A

AA

+=

1


44/54


Te .ee$%ac& *a'(le* a (orton o. teo"t("t +oltage an$ con+ert* t to a c"rrent c"rrentto+oltage a'(l)er#

Te crc"t con**t o. a %a*c a'(l)er tatcon+ert* te error c"rrent to an o"t("t+oltage :t a gan .actor9 A8an$ tat a*

an n("t re**tance9 R#

Te .ee$%ac& crc"t *a'(le* te o"t("t+oltage an$ (ro$"ce* a .ee$%ac& c"rrent9 I.%9

:c * n *"nt :t te n("t c"rrent9 I#


45/54


A**"'e te o"t("t * a o(en crc"t9 teo"t("t +oltage>

IAV zo=.ee$%ac& +oltage *>

ogVIfb =In("t *gnal +oltage

fbi II += I

zg

z

i

ozf

A

A

I

VA

+==1

:ere g * a con$"ctance .ee$%ac& tran*.e


46/54


!r

In("t c"rrent

Rif:t .ee$%ac&


)( IAIII zgfbi +=+=I

)1( zg

i

AII

+=

)1( zg

iiii

A

RIRIV

+

==

)1( zg

i

i

iif

A

R

I

VR

+==

A**"'e an$ ?a((le$ to o"t("t

ter'nal#

!r

In("t c"rrent

Rof:t .ee$%ac&


0=+=+ xgfb VVVV xgVV =

o

zgx

o

zxi

RAV

RVAVI )1( +==

)1( zg

o

x

xof

A

R

I

VR

+

==


47/54


E;"+alent crc"t o. *"nt *"nt .ee$%ac&crc"t or

+oltage a'(l)er


48/54


Ba*c n+ertng o(a'( crc"t * an e?a'(le o.*"nt*"nt con)g"raton#

In("t c"rrent *(lt* %et:een .ee$%ac& c"rrent an$error c"rrent#

S"nt o"t("t connecton *a'(le* te o"t("t+oltage .ee$%ac& c"rrent * ."ncton o. o"t("t+oltage#

2

2

RI

VA

IIwhere

RIV

i

ozf

ifb

fbo

==

=

=


49/54


A8 * o(enloo(tran*re**tancegan .actor


50/54



51/54


+

+

+

==

=

+

+

+

+

+=

=++

F

m

FFFC

F

m

i

ozf

F

oi

F

m

FFC

o

F

oi

F

om

C

o

Rg

RRrRR

Rg

I

VA

R

VI

Rg

RrRRV

R

VV

r

VI

R

VVVg

R

V

111111

1

011111

0


52/54

( )

( )

+=

+

+

+

++

==

=

=

F

z

z

i

ozf

F

Cz

FFF

C

F

Cz

i

ozf

Cm

C

mz

R

A

A

I

VA

R

RrARR

r

R

R

R

RrA

I

VA

Rrg

rR

gA

11

111

11


!(enloo( tran*re**tance gan .actor A8*

.o"n$ %6 *ettng RF

M"lt(l6 %6


53/54

Fee$%ac& A'(l)er

Input and output Impedances Summary

1# For a *ere* connecton at n("t oro"t("t9 te re**tance * ncrea*e$

%6


54/54

Fee$%ac& A'(l)er

ch 3 - feedback.ppt

Documents