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Differential Amplifiers (Ch. 22)p
김 영 석김 영 석
충북대학교 전자정보대학
2011.3.1. .
Email: [email protected]
전자정보대학 김영석 22-1
Contents22.1 The Source Coupled Pair
22.2 The Source Cross-Coupled Pair
22.3 Cascode Loads
22 4 Wid S i Diff A22.4 Wide-Swing Diff Amp
전자정보대학 김영석 22-2
22.1 The Source-Coupled Pair22.1.1 DC Operation
Max/Min Diff Input Voltage
Vvi THNGSn
D −= )(2
2β
iivvv DDIIDI
THNGSD
−=−= )(2
)(2
2121 β
WKPILiIivv
n
SSDSSDDIDIMAX
n
⋅⋅⋅
====2)0,( 21
β
Vvv DIMINDIMAX
n
Δ⋅=−=∴ 2
전자정보대학 김영석 22-3
Source-Coupled PairMax/Min Common-Mode(CM) Input Voltage
VVVDDSaturationinMVVV
THNCM
THNGD
−≥−≥ ) 1(
VVVVVDDV
GSCMMIN
THNCMMAX
Δ+=+=
22,1
Ex 22.2: Folded Cascode
VVVVDDV SGCMMAX 35.315.15.052 =−−=−Δ−=
VVVVVVVVVV
THPDCMMIN
THPGDTHPSGSD
SGCMMAX
65.09.025.0 −=−=−=+≤→−≥
전자정보대학 김영석 22-4
Source-Coupled PairCurrent-Mirror Load
55.15.005.12)(65.48.015.15
GSCMMIN
THNGDTHNSGCMMAX
VVVVVVVVVVVDDV
=+=Δ+=−≥=+−=+−=
)(7.1)(75.4
2
4
THNGDTHNIOUTMIN
THPGDOUTMAX
VVVVVVVVVVVVVDDV
−≥=−=+≤=Δ−=
Minimum Power Supply Voltage
nmmVmmmVVVVDD SG
50@50010050350 213min
==++=+Δ+=
λ
전자정보대학 김영석 22-5
Source-Coupled Pair22.1.2 AC Operation
)||(2)||)((
21
424221
ii
oodooddout
vvgvgiii
rrirriiv−
===−=
=−=
)||(
2
42
121
oomoutout
d
mgsmddd
rrgvv
vvvA
gvgiii
⋅=−
==
===−=
Ex 22.5/6
21 iidi vvv −
VVkkVArrgAAInm
oomd
D
/7.16)333||167(/150)||(10,50
42 ==⋅===
μμλ
pFCMHzCrr
f LLoo
dB 1@ 4.1)||(2
1
423 ==
⋅⋅=
π
전자정보대학 김영석 22-6
Source-Coupled Pair22.1.3 CMRR(Common-Mode Rejection Ratio)
11
2222,1 RiRigiRivv odod
m
dodgsc ≈+=+=
1
11
43
vg
ig
ivm
dm
dout ⋅−=⋅−=
)5.22(86~2
1
4,3
ExdBRgv
vAomc
outc −==
전자정보대학 김영석 22-7
Source-Coupled Pair22.1.4 Matching Considerations
])/()/([
2 LWLW
RRVVVVL
LTHNGSTHNOS
Δ−
Δ−⋅
−+Δ=
전자정보대학 김영석 22-8
Source-Coupled Pair22.1.6 Slew-Rate Limitations
L
SSout
CI
dtdVSlewRate ==
전자정보대학 김영석 22-9
22.2 The Source Cross-Coupled PairEliminate Slew-Rate Limitations of Source-Coupled Pair
Low Power
↓↑↓=>−↑−↓=>↑ 21423121 ,)(,)(, DDGGGGII iivvvvvv
Demerit: Limited Input Range
↑↓↑=>−↓−↑=>↓ 21423121 ,)(,)(, DDGGGGII iivvvvvv
Demerit: Limited Input Range
전자정보대학 김영석 22-10
Source Cross-Coupled Pair22.2.1 Current Source Load
531
2
)1/11(/1/1
/1/1
:)(1
9,3,1,0)1(
grgg
gR
ggg
RgR
vvCDM
CSMCGMCDMv
mLeq
mLeqs
i
≈+≈+
≈+
=
====
53
1
9
33333111
1:)(3
/1/1/1
gg
vv
CGM
grggggRgv
mm
s
g
mommmmLeqmi
=
++
33
10999
0)||)()(/1(2
||:)(9
fggv
rrgvvCSM
mmout
oomg
out ⋅−=
210995
3
31
3
1
1020)2(path M10M6,M2,M4,M41, from comes 2Factor
0)||)()(/1/1
/(2
CSMCSMv
vforrrggg
ggg
vv
ioomm
m
mm
m
i
out =⋅−+
=∴
11091042
6
2
1
0 )||)(/1/1
/1(2
10,2,0)2(
vforrrggg
gvv
CSMCSMv
ioommm
m
i
out
i
=⋅−+
−=∴
===
88
10910,94,32,1
6,5
12
:
)||)(/1/1
/1(4),2/()1(,
VVDDVVVDDVNote
rrggg
gvv
vFrom
THNSGCMMAX
oommm
m
ii
out
Δ−≈+−=
⋅+
=−
전자정보대학 김영석 22-11
531531
88
VVVVVVVVV THNTHNGSSDGSCMMIN
THNSGCMMAX
Δ++Δ++Δ=++=
22.3 Cascode LoadsHigh Gain
M6: M1/M2 Saturation 동작 보장
omommd rgrggA = )||( 244
2221
SSGSCMMIN
THNCSGCMMAX
VVVVVVVDDV
Δ+=+Δ−−=
21
13
전자정보대학 김영석 22-12
22.4 Wide-Swing Diff AmpCMR 개선
2)(,)(,)(: /, )1(
7,12,5,48,11,10,96,3,2,1 DDD
CM
IMIIMIIMIONBothPairPMOSNMOSMiddleV===
=
:/ , )2()(2
22)||)((
75
912,72,591
CM
IoIommv
ONPairPMOSOFFPairNMOSLowVI
IIrrggA
=++
=+=λλββ
2)||)((
)(,)(,0)(:/,)(
9
7,12,5,48,11,10,96,3,2,1 DDD
CM
IrrgA
IMIIMIMIONaiOSOaiN OSowV
==
===
β
)(0)()(: / , )3(
)()||)((
75,7,59
CM
IoIomv
IMIMIIMIOFFPairPMOSONPairNMOSHighV
IrrgA
====
+==
λλ
)(2
)||)((
)(,0)(,)(
75
1,7,51
7,12,5,48,11,10,96,3,2,1
IoIomv
DDD
II
rrgA
IMIMIIMI
+==
===
λλβ
2
, )(
91
75
m IG
GainSamegetTo
==>== ββββ
전자정보대학 김영석 22-13
)||( ,7,5 IoIomv rrGA =
22.4.1 Current Diff AmpLow Power, High Speed
min g
R 1=
전자정보대학 김영석 22-14
22.4.2 Constant Transconductance Diff-AmpFig 22.32: Constant Gain (Gm different)
Fig 22.34: Constant Gm
constant22 =+=+= ppnnmpmnm IIggg ββ
22.35 Figconstant =>=+∴ pn II
전자정보대학 김영석 22-15
전자정보대학 김영석 22-16
