Investigating CMOS Amplifier Design Using the Degrees of Design Freedom Method

158 Pages·2009·5.24 MB·English

Investigating CMOS Amplifier Design
Using the Degrees of Design Freedom
Method
Euisoo Yoo
Department of Electrical and Computer Engineering
McGill University
Montr´eal, Qu´ebec
May 2009
A thesis submitted to McGill University in partial fulfilment of the requirements of
the degree of Master of Engineering
(cid:13)c Euisoo Yoo, 2009
ACKNOWLEDGEMENTS
I’d like to start by thanking my supervisor, Professor Gordon Roberts, for the
opportunity to conduct my research and design with him and the group in the MACS
lab. With his enthusiasm, his inspiration, and his great efforts to explain things
clearly and simply, he helped to make research fun for me. I learned a great deal
under his supervision, which to me is so incredibly valuable. For this, I am eternally
grateful. ToallmyfriendsatMcGill,Ithankyouallforsuchamemorableexperience.
I will truly miss all of the interesting discussions, the all-nighters, and the pranks you
pulledonme. TheywerecertainlygreattimesthatIwillneverforget. Iwishtothank
my parents, my sister, my uncle, my aunt, my two cousins in Montr´eal for always
being there. Finally, I thank the McGill staff for their support with departmental
matters, keeping the servers alive and running, and for awards and financial support.
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ABSTRACT
A design methodology based on generating the performance space of amplifiers
bysweepingindependentcontrolvariableshasbeeninvestigated. Themethodisused
to optimize the performance of CMOS amplifiers with respect to gain, bandwidth,
noise, distortion and power directly in SPICE without the aid of mathematical mod-
els or external software routines. The method works in all SPICE programs from
Cadence to the student version of PSPICE. The technique is based on tuning the
voltage of specific nodes of the amplifier using a self-biasing current source technique
in conjunction with a replica amplifier circuit to span the entire performance space
with a resolution of choice. The method has been tested with discrete implemen-
tation of the design. Both single-stage and multi-stage amplifiers are considered in
this work. The method is generic, and it can be easily extended onto any amplifier
topology for any performance measure.
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ABRE´GE´
Unem´ethodologiedeconceptionoriginalebas´eesurlaproductiondel’espacedes
performances des amplificateurs en balayant les variables de contrˆole ind´ependantes
est examin´ee. Cette m´ethodologie peut optimiser des amplificateurs de CMOS par
rapport au gain, `a la bande passante, au bruit, `a la d´eformation et `a la puissance.
L’espace des performances est recherch´e directement dans les logiciels SPICE sans
l’aide d’aucun mod`ele math´ematique ou des logiciels externes. Cette m´ethode fonc-
tionne dans tous les logiciels SPICE, allant de Cadence `a la version d’´etudiant
de PSPICE. La technique est bas´ee sur la variation de tension dans des noeuds
sp´ecifiques de l’amplificateur en utilisant une source de courante d´ependente et, en
parrall`ele, un circuit d’amplificateur copie pour cr´eer l’espace des performances com-
pletavecuner´esolutiondechoix. Cettem´ethodologiea´et´etest´eaveclescomposantes
s´epar´ees. Desamplificateurs`a´etageuniqueet`a´etagesmultiplessontconsid´er´esdans
ce travail. Cette m´ethode est g´en´erique, et elle peut ˆetre facilement appliqu´ee sur
n’importe quelle topologie d’amplificateur pour n’importe quelle mesure de perfor-
mance.
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CLAIMS OF ORIGINALITY
This thesis contain the following original work
• Investigation of the design by degrees of freedom method in the following am-
plifier structures: common-source, common-gate, common-drain, differential
amplifier dicussed in Chapter 4.
• SeparationofthenodeV in1stand2ndstageinmastercircuitofamulti-stage
x
amplifier, using a different self-biased current source for each, to do DC biasing
for each of the amplifier topologies in Chapter 5.
• Partial space exploration approach to multi-stage amplifier design (cascaded
amplifier) and MATLAB program to do semi-automated partial space explo-
ration discussed in subsection 5.1.1.
• Divideandconquerapproachtomulti-stageamplifierdesign(two-stageopamp)
discussed in subsection 5.1.2.
• Control variable reduction approach to multi-stage amplifier design (folded
cascode op amp) discussed in subsection 5.1.3.
• Extension of design by degrees of freedom method to a fully-differential ampli-
fiers discussed in section 5.5.
• Design verification using discrete electronics described in Chapter 6.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
´ ´
ABREGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
CLAIMS OF ORIGINALITY . . . . . . . . . . . . . . . . . . . . . . . . . . . v
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Thesis Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Background on CMOS Amplifier Design . . . . . . . . . . . . . . . . . . 5
2.1 Classical Analog Design Overview . . . . . . . . . . . . . . . . . . 5
2.1.1 CMOS technology . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Why Integrated? . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.3 What is an Amplifier? . . . . . . . . . . . . . . . . . . . . . 8
2.1.4 Performance Metrics . . . . . . . . . . . . . . . . . . . . . 9
2.2 State of the art . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.1 g /I Synthesis Approach . . . . . . . . . . . . . . . . . . 22
m D
2.2.2 Computer-Aided Design based on Geometric Programming 27
2.2.3 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3 Design by Degrees of Freedom . . . . . . . . . . . . . . . . . . . . . . . . 32
3.1 Design by Degrees of Freedom Method . . . . . . . . . . . . . . . 32
3.2 Independent Control Variables . . . . . . . . . . . . . . . . . . . . 33
3.3 Self-Biased Current Source Circuit . . . . . . . . . . . . . . . . . . 38
3.4 Master-Slave Arrangement . . . . . . . . . . . . . . . . . . . . . . 44
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3.5 Performance Simulation and Data Mining . . . . . . . . . . . . . . 46
3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4 Single-Stage Amplifier Design . . . . . . . . . . . . . . . . . . . . . . . . 51
4.1 Common-Source Amplifier . . . . . . . . . . . . . . . . . . . . . . 51
4.2 Common-Gate Amplifier . . . . . . . . . . . . . . . . . . . . . . . 67
4.3 Common-Drain Amplifier . . . . . . . . . . . . . . . . . . . . . . . 69
4.4 Differential Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5 Multi-Stage Amplifier Design . . . . . . . . . . . . . . . . . . . . . . . . 73
5.1 Design Heuristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.1.1 Partial Space Exploration Approach . . . . . . . . . . . . . 74
5.1.2 Divide and Conquer Approach . . . . . . . . . . . . . . . . 75
5.1.3 Control Variable Reduction Approach . . . . . . . . . . . . 77
5.2 Cascaded Amplifier Configuration . . . . . . . . . . . . . . . . . . 77
5.3 Two-Stage Op Amp Configuration . . . . . . . . . . . . . . . . . . 82
5.4 Folded Cascode Op Amp Configuration . . . . . . . . . . . . . . . 90
5.5 Fully-Differential Design . . . . . . . . . . . . . . . . . . . . . . . 95
5.6 Comparison of the three methods . . . . . . . . . . . . . . . . . . 99
5.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6 Design Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.1 Self-Biased Current Source . . . . . . . . . . . . . . . . . . . . . . 104
6.2 Common-Source Amplifier . . . . . . . . . . . . . . . . . . . . . . 107
6.3 Two-Stage Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
A OCEAN code : Control Variable Sweep . . . . . . . . . . . . . . . . . . . 129
B MATLAB code : Partial Space Exploration . . . . . . . . . . . . . . . . 132
C MATLAB code : Processing Waveform . . . . . . . . . . . . . . . . . . . 139
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
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LIST OF TABLES
Table page
2–1 Node voltages and NMOS transistor’s region of operation. . . . . . . . 12
3–1 Number of design variables in different amplifier topologies. . . . . . . 37
4–1 Trade-offs for the CS Amplifier. . . . . . . . . . . . . . . . . . . . . . . 67
4–2 PerformanceresultsforCS,CG,CDandDIFFamplifiersinCMOSP18
technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4–3 Trade-offs for the CG Amplifier. . . . . . . . . . . . . . . . . . . . . . 69
4–4 PerformanceresultsforV =1.3VV =1.1VV =0.7VW =40µmW =20µm
x oQ p n3 p3
W =40µm Amplitude=100µV. . . . . . . . . . . . . . . . . . . . . 69
p2
4–5 Trade-offs for the CD amplifier. . . . . . . . . . . . . . . . . . . . . . . 69
4–6 Trade-offs for the DIFF amplifier. . . . . . . . . . . . . . . . . . . . . 70
5–1 Trade-offs for the cascaded amplifier using partial space exploration
method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5–2 Performance results for Cascaded, Folded Cascode, and Fully Differen-
tial Folded Cascode amplifiers in CMOSP18 technology . . . . . . . 82
5–3 Performance comparison between divide and conquer approach and
traditional simulation approach. . . . . . . . . . . . . . . . . . . . . 87
5–4 Performance comparison between compensated divide and conquer ap-
proach and traditional simulation approach. . . . . . . . . . . . . . 89
5–5 Trade-offs for the 1st stage of the 2-stage operational amplifier using
divide and conquer method. . . . . . . . . . . . . . . . . . . . . . . 90
5–6 Trade-offs for the 2nd stage of the 2-stage operational amplifier using
divide and conquer method. . . . . . . . . . . . . . . . . . . . . . . 90
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5–7 Trade-offs for the 2-stage operational amplifier using divide and con-
quer method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5–8 Control variable reduction method. . . . . . . . . . . . . . . . . . . . . 94
5–9 Trade-offs for the folded cascode amplifier using control variable reduc-
tion method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5–10 Trade-offsforthe1ststageofthefully-differentialtwo-stageoperational
amplifier using divide and conquer method. . . . . . . . . . . . . . . 97
5–11 Trade-offs of the fully-differential two-stage operational amplifier using
divide and conquer method. . . . . . . . . . . . . . . . . . . . . . . 98
5–12 Trade-offs for the fully-differential folded cascode amplifier using con-
trol variable reduction method. . . . . . . . . . . . . . . . . . . . . . 99
6–1 Performance measures for changing V for VoQ=0.6 N=1 P=1 VDD=4V.108
g
6–2 PerformancemeasuresforchangingV forVoQ=0.6N=1P=1VDD=1.2V.108
g
6–3 PerformancemeasuresforchangingV forVg=2.97N=1P=1VDD=1.2V.109
oQ
6–4 PerformancemeasuresforchangingN forVg=2.8VoQ=0.5P=1VDD=4V.113
6–5 PerformancemeasuresforchangingN forVg=2.8VoQ=0.5P=1VDD=1.2V.114
6–6 PerformancemeasuresforchangingP forVg=2.8VoQ=0.7N=1VDD=4V.114
6–7 PerformancemeasuresforchangingP forVg=2.8VoQ=0.7N=1VDD=1.2V.115
6–8 PerformancemeasuresforchangingV forVoQ=1.5Vmid=2.825Md=1
gd
Mg=1 Mp=1 Mp2=1 Mn2=1. . . . . . . . . . . . . . . . . . . . . . 121
6–9 PerformancemeasuresforchangingM forVgd=1VoQ=1.5Vmid=2.825
d
Mg=1 Mp=1 Mp2=1 Mn2=1. . . . . . . . . . . . . . . . . . . . . . 121
6–10 PerformancemeasuresforchangingM forVgd=1VoQ=1.5Vmid=2.825
g
Md=1 Mp=1 Mp2=1 Mn2=1. . . . . . . . . . . . . . . . . . . . . . 124
6–11 PerformancemeasuresforchangingM forVgd=1VoQ=1.5Vmid=2.825
p
Mg=1 Md=1 Mp2=1 Mn2=1. . . . . . . . . . . . . . . . . . . . . . 125
6–12 PerformancemeasuresforchangingM forVgd=1VoQ=1.5Vmid=2.825
n2
Mg=1 Mp=1 Mp2=1 Md=1. . . . . . . . . . . . . . . . . . . . . . . 125
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6–13 PerformancemeasuresforchangingM forVgd=1VoQ=1.5Vmid=2.825
p2
Mg=1 Mp=1 Md=1 Mn2=1. . . . . . . . . . . . . . . . . . . . . . . 126
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