Amplifiers (Ch. 21)p

김 영 석김 영 석

충북대학교 전자정보대학

2011.3.1. .

Email: kimys@cbu.ac.kr

전자정보대학 김영석 21-1

Contents21.1 Gate-Drain Connected Loads

21.2 Current Source Loads

21.3 The Push-Pull Amplifier

전자정보대학 김영석 21-2

21.1 Gate-Drain-Connected Loads21.1.1 Common-Source(CS) Amplifiers

21 )

1(m

min

out

gg

vv

⋅−=

221

2

1||||1,m

oom

oin grr

gRR ≈=∞=

E 21 1Ex 21.1

outv −= drain in the resistance

Lm

in

RgRg

v

+−= 2

/1||/1

sourcein the resistance

전자정보대학 김영석 21-3

sm Rg +1/1

Miller’s TheoremMiller’s Theorem

전자정보대학 김영석 21-4

Frequency ResponseFrequency Response of CS

)1)(1(

/ 21

outin

mm

in

out

ffj

ffj

ggvv

++−=

)(1),(

)2/(1),2/(1

21 sgMOoutgsMIsin

outoutinin

outin

CCg

CCR

ffwhereff

+=+=

==

ττ

πτπτ

)1(),1(1

21

2

11

2

m

mgdMO

m

mgdMI

m

ggCC

ggCC

g

+=+=

The Right-Half Plane Zero: Unstable

1

11 )1(

0

m

gdom

out

out

gC

jwRgv

vzero

−

==>

1

1

1

2

)(1

mz

oogd

m

in

out

Cgf

RCCjwg

v

π=

++−=

전자정보대학 김영석 21-5

12 gdCπ

Ex 21.2: Mag/Phase

AIVAVA

ggA Dmv 20@1/150

/150

2

1 =−=−=−= μμμ

ffj

ffj

Avv

VAg

i

v

s

out

m

)1)(1(

/1502

++−=

μ

Ex 21.3: vout @400MHz

GHfMHzfMHzfwhereff

zoutin

outin

9.11,331,58 ===

MHzTpsttvvdB

vv

d

s

out

s

out

400/1@35036050

50 ,1.020||

≈>°

°=∠−=−=

MHzTpstT dd 400/1@35036050 =≈=>=°

전자정보대학 김영석 21-6

Gate-Drain-Connected LoadsCS Current Amplifier (Transimpedance Amp)

2343

3

1,1||||1

mo

moo

min g

Rg

rrg

R ≈≈=

21

3

11

mm

min

outR g

ggi

vA ⋅⋅−==

CS Amplifier with Source Degeneration

||12

Lmout

Rgv

)1(

11

2

ms

m

in

out

RRRg

R

gv +

−=

)1(, 111 omsooin rgRrRR ++=∞=

전자정보대학 김영석 21-7

21.1.2 Common Drain (Source Follower) Amplifier

sourcethetoconnectedRes.outvA

1source theinto looking Res.source the toconnected Res.in

outv v

A+

==

21

1

11 m

gg

g

+−=

21

21

1||1,mm

oin

mm

ggRR

gg

=∞=

전자정보대학 김영석 21-8

21.1.3 Common Gate Amplifier

12

1

1

source in the Res.drain in the Res. m

in

outv

gvvA =+==

1

1 ,1 oin

m

RR

g

==21 mm gg

전자정보대학 김영석 21-9

21.2 Current Source Loads21.2.1 CS Amplifier

F R

21211 || , ),||( oooinoomin

outv rrRRrrgv

vA =∞=−==

Frequency Response

211 )/1)(/1(/1)||()(

ti

zoomv fjffjf

fjfrrgfA++

−⋅⋅−=

211211 )|||)](|/11([21,

|)]|1([21

)/1)(/1(

oovgddgout

svgdgsin

outin

rrACCf

RACCf

fjffjf

ππ ++=

++=

++

1

1

2 gdm

z Cgfπ

=

전자정보대학 김영석 21-10

Freq Response of CS Amp with Current Source Load

Ex 21.6: Freq Response of CS Amp

69133323.2350/333)4||5(/150||

fFffCdBVVMMVAA

in

v

=⋅+===⋅= μ

2009.11,9,3.2

826

SPICEfMHfGHzfMHzfMHzf

fFffC

zoutin

out

====+=

!! ' 200

inaccurateisfcalculatetoTheoremsMillerSPICEfromMHzf

out

out =

전자정보대학 김영석 21-11

Freq Response of CS Amp with Current Source Load

Pole Splitting (Generic Model)

outin

zmmv fjffjf

fjfRgRgfA)/1)(/1(

/1)( 2211 ++−

⋅−=

mcmccin

CgRRgCRRgCCRCC

fππ )(2

1]))1(()[(2

1

122122122

≈++++

≈

m

cc

cmout

gf

CCCCCCCgf

πsTheoremMiller' of that fromdifferent

)(2

2

2211

2

++≈

c

mz C

gfπ2

2=

전자정보대학 김영석 21-12

Freq Response of CS Amp with Current Source Load

Ex 21.7: Repeat Ex 21.6 using the generic model

22.2||,6

2,3.23,100

21222

1111

MrrRfFCC

fFCCfFCCkRR

oodg

gdcgss

Ω====

======

/10)6.21(/1)(/150)6.21()(

1

12

VAExRgenericgVAExggenericg

sm

mm

====

μμ

)911932:621(9.11,240,3.2

50/333)4||5(/150||

21

GHzfMHzfMHzfExGHzfMHzfMHzf

dBVVMMVAA

z

v

=====⋅= μ

accurateisModelGeneric 200

)9.11,9,3.2:6.21(SPICEfromMHzf

GHzfMHzfMHzfEx

out

zoutin

====

accurate is ModelGeneric

전자정보대학 김영석 21-13

Freq Response of CS Amp with Current Source Load

Ex 21.8: Repeat Ex 21.6 When Rs=0

9)22.2)(8(2

1)||)((2

1

21211

oodggd

f

MHzMfrrCC

f =Ω

=+

≈ππ

before as same 2

zff ∞≈

전자정보대학 김영석 21-14

Freq Response of CS Amp with Current Source Load

Ex 21.9: Pole Splitting

8411

11 1

==≈

≈+= gdc

kHzf

pFCpC

811)1663233231(2

1/150 )(2

8.4100)2.2/1501(2)(2

2

1221

=++

⋅=

++≈

=Ω⋅⋅

=≈

cmout

mc

MHzpFffffpF

pFVACCCCCC

Cgf

kHzkMVApFRRgC

f

πμ

π

μππ

)/1(59.12

1,2312

/1502

)1663.233.231(2)(2

12

2211

====⋅

==

⋅+⋅+⋅++

mscs

unc

mz

cc

gRMHzCR

fMHzpVA

Cgf

pFffffpFCCCCCC

ππμ

π

ππ

Splitting Pole1pF Add =>csc p

전자정보대학 김영석 21-15

Frequency Response of CS Amp with Current Source Load

Cancelling the RHP Zero

U t blM iPhL)(ZRHP)/1)(/1(

/1)( 0

>>++

−⋅−=

outin

zvv

ffjffjf

fjfAfA

With a Resistor

UnstableMarginPhaseLess)(ZeroRHP =>=>zf

11 resistorawith )1(2

112

1

22

−⋅⋅==>

⋅⋅=

zm

c

z

mc

z

Rg

Cf

gC

fππ

Margin) Phase Zero(MoreLHP,1 )2(,,1 )1(22

=>∞== zm

zzm

z fgRf

gR

전자정보대학 김영석 21-16

21.2.2 The Cascode AmplifierCascode=>Less Miller Effect=>Better Freq Response

opmponmnocasocasmnin

outv rgrgRwhereRgv

vA =⋅−== || 22

ocasoin

in

RRR =∞= ,

전자정보대학 김영석 21-17

Cascode AmpEx 21.12

729]|)|1([100,100

11 psCACRfCkR

gdvgssin

Ls

=++===

τ

)Miller Less todue 3.2:(2182

1

335||)( 2232

MHzCSMHzf

nsCrgrgCCCR

in

loadopmponmngdgdloadocasout

==

=⋅≈++=τ

)Node ImpedanceHigh todue 240:(4752

12

MHzCSkHzfout

out

in

==πτ

πτ

out

전자정보대학 김영석 21-18

Cascode as Transimpedance Amp

oon

ocasp

inin

rR

rR

ivR

22

1≈

+=

−=

out

on

ocasp

onmn

in

RRrgrgvr

Rr

gi

||||

22

22

2

==

++

ocaspocasnopmponmnin

RRrgrgi

|||| −=−=

전자정보대학 김영석 21-19

21.2.3 The Common-Gate Amplifier

onmnin

outv rgv

vA ⋅≈=

onomn

in rRgR == ,1

전자정보대학 김영석 21-20

21.2.4 The Source Follower (Common-Drain Amp)Without Body Effect

212

21 1||1

||

oo

oo

in

outv

rrg

rrvvA ≈

+==

221

2

2

1||||1,m

oom

oin

m

grr

gRR

g

≈=∞=

With Body Effect

r||1

mmbmbm

m

ob

omb

in

outv ggwheregg

g

rgg

rg

vvA

11

||11

||=

+=

+≈

+== η

η

mbmo

mbmoin

mbm

ggr

ggRR

gg1||1||1||1, ≈=∞=

전자정보대학 김영석 21-21

SF(Source Follower)Level Shifting

mVVvVvvVvvvv

THPIN

THPINOUTTHPSGOUTSDIN

280 :

min,

min,

−=−=

−−=−≥=

mVVvvmVmVVVDDvv

SGOUTIN

OUTIN

500 85015012:

max,max,

max,max,

=−=

=−=Δ−=

Input Capacitance

smallveryCACCQC

CvAvCvQ

ddIN

IN

sgINvINdgININ

:)1(

)(

≈−+==

⋅Δ⋅−Δ+⋅Δ=

smallveryCACCv

C dgvsgdgIN

IN :)1( ≈+Δ

전자정보대학 김영석 21-22

SF(Source Follower)Frequency Behavior

gdgss

smgsmd

g

CCjwZvgfvgfi

+⋅⋅+=⋅=

)(1)()(

gdgss

gdgss

mm

RZifCCR

R

CCjwZgfg

+

+⋅⋅+=

)(11

)(1)(

Rinto source=Resistor+Inductor: Unstable

ssm

gdgss

mmsourceo RZifg

jwgfg

R =+==)(1

)(1

int

If Zload=Capacitor, Ringing

If Zs=Inductor, Rinto source~ Negative Resistor

전자정보대학 김영석 21-23

SF(Source Follower)Ex 21.13: SF as an Output Buffer

Without Output Buffer, Gain of Cascode Drops due to low RL

) (218=in OnlyCascodeasSameMHzf

)100)(512(5073

) 475(1~2

1

==≈⋅===

=loadocas

out

CascodeforfFCKfFKfCCCwhere

OnlyCascodeforkHzMHzCR

fπ

95.053310

10/1

)100)(5.12(507.3

,

,

=+

=+

=

==≈⋅===

widemload

loadSFv

loadgdSFINload

kk

gRRA

CascodeforfFCKfFKfCCCwhere

47595.0500/875.1

,,

2.9,,

,

=⋅=⋅=

=⋅=

SFvCascodevv

Tablemwidem

widemload

AAAVmAgKgwhere

g

,,

전자정보대학 김영석 21-24

SF(Source Follower)Class A

M5/6 Sourcing Current All of the time

Class AB Output Buffer Using SFClass AB Output Buffer Using SF

Vin High: M6 OFF, VG3,4 Low, M1 ON, M2 OFF => Sinking Current

Vin Low: M6 ON, VG3,4 High, M1 OFF, M2 ON => Sourcing Current

Demerit: Vout,max not close to VDD

전자정보대학 김영석 21-25

21.3 The Push-Pull AmplifierVout.max=VDD-VTHN: Class AB SF

Rail-to-rail output Swing: Push-Pull Output Buffer

Class AB

iin>0: VG2,VG1 up, M2 OFF, M1 ON

P lli C tPulling a Current

iin

Push-Pull Amplifieriin>0: VG,MOP up => MOP OFF,ID,MFCP up, ID,MFCN down, VG,MON up => MON ON, Pull

iin MOP ON, Push

I d I V d > MON OFFID,MFCP down, ID,MFCN up, VG,MON down => MON OFF

Gainout RggvA )( + loadmopmonin

outpullpushv Rggv

A )(, +−==−

Note: VG,MOP up => VG,MON up, VG,MOP down => VG,MON down

VG,MON/ VG,MOP are shorted

전자정보대학 김영석 21-27