ec1012-3-multi2021v1

1. Introduction to the Design of Analog ICs Idea-Chip Micro-Macro CMOS Modeling OpAmp Lab 1/85
Design of
Analog Integrated Circuits
Prof. Ashis Kumar MaL
akmal@ece.nitdgp.ac.in
Department of Electronics & Communication Engg.
National Institute of Technology Durgapur
Analog IC Design
Ashis Kumar MaL

Touching Minds
Analog vs Digital
Transducers
If it can be done by digital, don't use analog!
Analog IC design is complex...
Background in physics, electronics,
information and control theory,
signal processing, communications
Variety of state-of-the-art solutions
High dependence from technology
Modeling skills
Complex EDA tools
...but still necessary!
Most modern ICs are
really mixed-signal
Touch
screen
Audio
input/output
Temperature
sensing
Accelerometer
Supply
RF
frontend
Preamp
Power
manager
DAC
Reference
Imager
Battery
manager
Magnetometer
Light sensing
PLL
μP
FPGA
ADC
μC
DSP
Memory
VCO
AGC
Filter
LNA
Mixer
PA
Communications
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
1/27
3. Multi-Stage OpAmps
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
2/27
1
Two-Stage Topologies
2
Frequency Compensation
3
Miller Effect
4
Design Space
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
3/27
1
Two-Stage Topologies
2 Frequency Compensation
3
Miller Effect
4
Design Space
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
4/27
Splitting Functions
Single stage CMOS OpAmp limitations:
Large
output
range
High gain:
cascoding
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
5/27
Splitting Functions
Single stage CMOS OpAmp limitations:
High gain:
cascoding
Large
output
range
Introducing two-stage architectures:
Improved dynamic
range performance
Area and power
overheads...
Frequency compensation required!
High gain
input stage
(low-noise amp,
preamp)
Large full-scale
output stage
(power amp,
output buffer)
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
8/27
1
Two-Stage Topologies
2 Frequency Compensation
3
Miller Effect
4
Design Space
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
9/27
Single Stage OpAmp Case
Basic control theory:
OpAmp
Passive
network
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
10/27
Single Stage OpAmp Case
Basic control theory:
Single pole amplifier:
OpAmp
Passive
network
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
11/27
Single Stage OpAmp Case
open
loop
Single pole amplifier:
-20dB/dec
follower
root
locus
Barkhasuen criteria:
Intrinsically stable!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
12/27
Two-Stage OpAmp Case
Double pole analysis:
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
13/27
Two-Stage OpAmp Case
Double pole analysis:
root
locus
in order to
cover up to H=1
dominant
pole splitting
is required!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
14/27
Two-Stage OpAmp Case
Double pole analysis:
open
loop
root
locus
-20dB/dec
follower
-40dB/dec
in order to
cover up to H=1
Barkhasuen
criteria:
Phase
margin
dominant
pole splitting
is required!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
15/27
1
Two-Stage Topologies
2
Frequency Compensation
3
Miller Effect
4
Design Space
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
16/27
Principle of Operation
Transimpedance amplifier:
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
17/27
Principle of Operation
Transimpedance amplifier:
equivalent input
impedance seen
from source
Miller effect:
equivalent output
impedance seen
from amplifier
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
18/27
Pole Adjustment
Transcapacitive impedance case:
Miller
compensation
two-stage OpAmp
small signal
model
dominant
pole
second
pole
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
19/27
Practical Example
Two-stage single-ended Miller-compensated OpAmp topology:
M8
M5
M7
M1
M2
M3
M4
M6
stage-1
stage-2
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
20/27
Practical Example
Two-stage single-ended Miller-compensated OpAmp topology:
M8
M5
M7
step response
unstable
M1
M2
M3
M4
M6
slow
stage-1
stage-2
time
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
21/27
1
Two-Stage Topologies
2
Frequency Compensation
3
Miller Effect
4
Design Space
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
22/27
Design Variables
Single-ended Miller OpAmp example:
M8
M7
M5
M1
M2
M3
M4
M6
25 design
variables!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
23/27
Design Variables
Single-ended Miller OpAmp example: Device matching groups:
Current biasing
M8
M7
M5
M1
M2
M3
M4
M6
25 design
variables!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
24/27
Design Variables
Single-ended Miller OpAmp example: Device matching groups:
Current biasing
M8
M7
M5
M1
M2
Null systematic offset
M3
M4
M6
25 design
variables!
8 design
variables!
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
25/27
Design Equations
Single-ended Miller OpAmp example:
M8
M7
M5
M1
M2
M3
M4
M6
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
26/27
Design Equations
Single-ended Miller OpAmp example:
M8
M7
M5
M1
M2
M3
M4
M6
Analog IC Design
Ashis Kumar MaL

Touching Minds
3. Multi-Stage OpAmps Two-Stage Compensation Miller Design
27/27
Design Equations
Single-ended Miller OpAmp example:
strong inversion
forward saturation
for all transistors
M8
M7
M5
M1
M2
M3
M4
M6
performance
resources
Analog IC Design
Ashis Kumar MaL