Chapter. 19

23年 4月 21日 Mobile Communication Lab. (http://mobile pknu.ac.kr)

1

Chapter. 19Chapter. 19

Negative Feedback


2

< Reference >

⑴ 전압귀환 출력전압이 안정 ( 낮은 출력 임피던스 )

⑵ 전류귀환 출력전류가 안정 ( 높은 출력 임피던스 )

⑶ 비 반전 입력 구동 높은 입력 임피던스

⑷ 반전 입력 구동 낮은 입력 임피던스


3

< Ideal Negative feedback >

• VCVS : Zin=∞ , Zout=0 , 출력전압 안정 ,

• ICVS : Zin=Zout=0 , transresistance Amp.(rm) ,

• VCIS : Zin=Zout=∞ , transconductance Amp.(gm) ,

• ICIS : Zin=0 , Zout=∞ , 전류이득 안정 ,

vin

outA

V

V

in

out

i

V

in

in

V

i

iin

outA

i

i

반전구동

( 입력전류원 )

비반전구동


4

⑴ VCVS • 入力 Imp. 大

• 出力 Imp. 小

• 전압이득 안정

+

-Vin

Verror

V2

Vout

V1

rin AOL

R2

R1V2OLAA


5

outBVV 2 ))//(

)//((

12

1

12

1

RR

R

rRR

rRB

in

in

outinerror BVVVVV 21

)( outinerrorout BVVAAVV

inout AVVAB )1( CLin

outA

AB

A

V

V

1

1

21

1

1 R

R

BBA

A

BA

AA

OL

OL

OL

OLCL

BAError

OL1

%100%


6

※

outOL

CLout

inOLCLin

rBA

Z

rBAZ

1

1

)1(

)(

)(

※

BAOL11

BA

V

OL

off

1

비선형 왜곡 ( Nonlinear distortion )

배 감소

※ 출력 offset voltage 감소


7

R2

+

-Vin

R1

iinVout

⑵ ICVS

+

Verror

+

-

iin

iin

R2

Vout+

-

+ -

AOL

-

• 入力 Imp. 小

• 出力 Imp. 小

( The inverting Amp. )

1

1

2

R

Vi

R

RA

inin

CL


8

errorout VAV

2

2

2

)1(

0

0

RiVA

A

RiVA

V

RiVV

inout

inoutout

inouterror

21

RA

A

i

V

in

out

(K.V.L)

2R (Transresistance)전달저항

( 전류 - 전압 변환기 )


9

● B=1

+

-R2

전류원

( 이상적으로 무한한 임피던스 )

12

R

B


10

※ A

Rr CLin

1

2)(

A

R

i

V

RiVA

RiVAV

VRiV

in

error

inerror

inerrorerror

errorinout

1

)1(

0

2

2

2

2

※

A

rr

outCLout

1

)(

+

- VoutArin(CL)

rout(CL)


11

19-5 The VCIS19-5 The VCIS

V1

V2

Verror

+

-

KVL+

-

V2

Vout


12

• 入力 Imp. 大

• 出力 Imp. 大

• 전압 - 전류 변환기

• 안정한 전달 컨덕턴스

in

out

V

i

ARR

R

Vi

ViA

RRRi

VARR

RRRi

VARR

RV

VVRRR

V

inout

inoutout

inout

inout

inerrorout

211

211

21

121

21

1

121

)1

)((

)1

(

(K.V.L);

inin

outg

RARR

RV

i

1211

11


13

(Ref.)

11

21

2121

2121

21

1

1))(

1(

11

1

1

RR

RR

RRBRRV

iRR

VA

RR

Vi

RR

RB

BAB

AA

in

out

inCLoutout

CL


14

※ 入力 Imp.

inCLin

inin

in

ininerror

ininerror

errorerror

outerrorin

outinerror

rABr

rABi

V

irV

irABVAB

ABVV

BVVV

BVVV

)1(

)1(

)1()1(

)(


15

※ 出力 Imp.

1

2

21 )(

RiV

VVV

RRiV

VAV

outin

inerror

outout

outerror

‥‥ ①

‥‥ ②

‥‥ ③

②,③ ①

outout

outoutoutin

iRARi

RiRiRiVA

12

211

)1(

)(

0

Thevenin

등가출력전압


16

1)(

1

1

)1(

)1(

)1(

RAZ

RAi

V

iRAV

CLout

out

out

outout

R2Zout


17

19-6 The ICIS Amplifier19-6 The ICIS Amplifier

Verror

+

-

Vout

021 RRerror VVV (K.V.L)

+ -

-

+

+

- -iout

iout-iin

iin


18

12

12

)(

)(

12

RiiRi

RiiRi

VVV

outinin

inoutin

RRerror

outerror VA

V1

‥‥ ①

‥‥ ②1)( RiiRiV inoutLoutout

121 )(])([1

RiiRiRiiRiA

outinininoutLout

A

1②①


19

1

12

121

121

121

)1(

)1(

])1([))1((

)()(

)(])([1

RAR

RAAR

i

i

RAARiRARi

RiiARAiRiiRi

RiiRiRiiRiA

Lin

out

inLout

outinininoutLout

outinininoutLout

A >> 1 이므로

BR

RR

AR

RRA

ARR

RRA

i

iA

Lin

outi

1)()(

1

21

1

21

1

21


20

※ Ref.

• 반전 전압 귀환

• 전류 귀환

1B )1()1( AAB

Fout RAr )1(

+

-

RF

RL

+

-RF

RL

출력전류와의 관계

1)(2

)( )1(1

RAZAB

RZ CLoutCLin

※ ※


21

19-7 Bandwidth19-7 Bandwidth

unityCLCL

CLCL

CL

CL

fAffA

fA

Af

AB

AA

fABf

2)(2

2)(2

2)(2

1

)1(


22

BAf

f

ffjBA

AA

AB

AA

ffj

AA

midc

cmid

midCL

CL

c

mid

1

1

1

1代入 개방루프 차단 주파수

OLmidCL fBAf )1()(2


23

☆ ☆ Bandwidth and Slew-rate DistortionBandwidth and Slew-rate Distortion

(max)max

max(max)

2

2

p

R

Rp

V

Sf

f

SV

)(2(max)

max)(2

2 CL

Rp

CL

f

SV

ff


24

R2

+

-

rout

AVerror

Vin

R1

+

-

V2

RL

Vout

VF Voltage


25

outoutoutoutin

outoutoutin

outoutinerror

VirBVVA

VirVVA

VriAV

)(

)( 2

)(1

)1(

CLoutout

outout

outoutout

ri

V

AB

r

VABir

0

0


26

R2

+

-

rout

AVerror

Vin

R1

+

-

V2

Vout

Iin

Iout-Iin

Iout

11

2

R

V

R

Vi

inout


27

outoutoutoutout

outinoutoutout

outinoutoutoutin

iRVriiAR

iRiiRriAV

iRiiRriVVA

11

122

122

)(

)()(

outRr

Routoutout

iRAVV

ViRAri

out 1

1

)1(

)1(

2

2

0


28

errorRr

Rrerror

AVVV

VVAV

out

out

2

2※

outin iRAVVA 12 )1()(

1)(

1

1

12

)1(

)1(

)1(

)1(

RAri

V

iRAV

iRAAV

iRAAV

CLoutout

out

outout

outin

out


29

11

2

R

V

R

Vi

inout

R2

+

-

Vin

R1

+

-

V2

Iin≒0Iout

Iout

(+) 단자 Vin 이 (-) 단자 V2 로 boostrapping


30

outerror VAV 1

2

RiV

VVV

outin

inerror

)( 21 RRiV outout

outout

outoutin

outoutoutin

iRAiR

iRARiAV

RiRiRiVA

12

12

211

)1(

)1(

)(0


31

+

-

R1

R2

Vin

V2 Vout

iout

outout iRV 2

1)(

1

)1(

)1(

RAri

V

iRAV

CLoutout

out

outout

outoutout

outin

iRRiiRR

RR

RiAV

1211

21

2

))((

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Chapter. 19