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ANU GUPTA EEE
Analog I C Design MEL G632
BITS Pilani Pilani Campus BITS Pilani Pilani Campus Anu Gupta
AICD Lecture 1
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Introduction
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Instructor-in-charge : ANU GUPTA Email (I/C): [email protected]
Analog I C Design MEL G632
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The objective of this course is to teach
analog integrated circuit design using
today’s technologies and in particular,
CMOS technology.
Objective
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The (electronic) world is going Digital,
why Analog?
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While many applications have replaced much analog circuitry with their digital counterparts, the need for analog circuit design is actually growing.
REASON 1------- Consumer-focused electronics have become the driving force of
industry, But , consumer electronics has become all-digital, networked,
sophisticated, and almost independent of time, place, physical embodiment, and content.
Users expect their tailored audio and video content when, where, and how they want it, to their own schedule and convenience.
NEED
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Ans.---As the digital demands have increased, they have increased the demands on analog as well, which is good for R&D and production investment. Ironically, new requirements for features in digital cell phones are dictating the needs for new analog functions.
And in turn, the increased analog capability has enabled more the
desired digital functionality and performance, as well. So we have one of the few cases where a positive feedback loop
is for good Example---Electronic application in demand
CELL PHONE
Reason 1--Consumer-focused electronics
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The key components of a basic handset are the radio, the power management, and the analog and digital baseband processing.
Basic Digital Handset
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Interesting fact: There's more analog in a digital
handset than in an analog model
Analog in digital handset.
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In a digital handset, --convert the voice signal to a digital stream (with an "analog" ADC). ---But before conversion, need to filter it (using an analog filter). --What comes out to your ear must be converted from digital to analog.(DAC) --And there's an analog filter there to clean up that signal. Getting the signal up onto the RF carrier, ---power amplifier (PA), --analog circuitry is needed to control the PA to ramp it up and down, and to
control the power,
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Putting the signal up on the air waves generally requires turning bits into a modulated carrier, which requires DACs and some filters (more analog parts).
On the receive side, what comes down from the RF
carrier is a modulated signal that needs ADCs to decompose the signal into quadrature components.
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The battery and power management CIRCUIT
that's needed to handle all the new digital
"stuff“ that's being packed into the newer
models, like things to manage a color display,
and the backlighting for it, high-performance
audio, and so on.
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Modern Handset
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• Higher resolution camera---analog image processing required to interface a multi-
megapixel camera sensor to the digital processor,
• Music-player phones with iPod-like capabilities----high-quality playback digital-to-
analog converters (DACs) and headphone driver amplifiers for audio playback.
• TV reception is a new feature emerging in cell phones----keeping the display
brightly lit to watch a video clip without consuming too much power requires power
management. power-management and battery-monitoring/charging functions needed
to maximize battery life while powering all the new features.
• Emerging TV-related feature is the ability to play back recorded still photos and
short video clips from the phone to a TV set. This requires creating an analog video
signal from the digitally-stored photo or video clip.
• Games---improved graphics capability, user interfaces, and even sound effects.
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Also, as the clock speed of digital circuitry
approaches 1 GHz, analog effects in these digital
circuits are playing an important role in the circuit
behavior.
Reason2- High speed
Which Analog circuits are important?
• If not for the multitude of analog and mixed-signal components that vendors have
developed in the past decades, the digital media river would slow to a trickle. It takes
countless A/D and D/A converters—audio, video, RF—to make it possible.
• It also takes basic small-signal amplifiers, audio through RF power amplifiers,
• disk-drive read/write circuitry,
• motor controls, line drivers and receivers, transmitters,
• power-supply components,
• touch-screen interfaces, display drivers,
• thermal sensors and fan controls,
and much more, to make the digital world possible.
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Analog IC Design
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The aim of this course is
to help students conceive, develop, debug
analog integrated circuits by presenting a
concise treatment of the wide array of
knowledge required by an analog IC
designer.
Aim while teaching
Approach to be followed a. Develop a firm background on technology and
modeling
b. Present analog integrated circuits in a hierarchical, bottom-up manner
c. Emphasize understanding and concept over analytical methods (simple models)
d. Illustrate the correct usage of the simulator in design
e. Develop design procedures that permit the novice to design complex analog circuits
(these procedures will be modified with experience)
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Presenting the fundamentals required to build high-
performance analog systems, -----will help to take the
mystery out of analog design.
In all cases , emphasis on the most important and
fundamental principles as they pertain to state-of-the-art
analog design.
Emphasis
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Course Handout
Component Duration Weightage
Date, & Time Remarks
Mid-semester Test 90 min 25 OB
Analog design project / take home weekly lab-assignments
continuous 40 Spread throughout the semester
OB
Comprehensive 3 hrs. 35 CB
100
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• Basic knowledge about single stage amplifiers
• Modelling
• AC., DC. Analysis techniques
• Frequency response analysis
• Negative feedback
Required background knowledge
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• Analog Integrated Circuit Design
• Technology Impact on Analog IC Design
• Analog Signal Processing functions
• Notation, Symbology and Terminology
• Summary
Introduction
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Geometry is an important part of the design Electrical Design →Physical Design →Test
Design Usually implemented in a mixed analog-digital
circuit Analog is 20% and digital 80% of the chip area Analog requires 80% of the design time Analog is designed at the circuit level Passes for success: 2-3 for analog, 1 for digital
Unique Features of Analog IC Design
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The Analog IC Design Flow
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Electrical Aspects-Topology, W/L values, and dc currents
Analog IC Design - Continued
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Physical Aspects-(Layout)
-Implementation of the physical design including:
- Transistors and passive components
- Connections between the above
- Busses for power and clock distribution
- External connections
Testing Aspects
-Design and implementation for the experimental verification of the circuit after fabrication
Analog IC Design - Continued
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Comparison of Analog and Digital Circuits
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In general, analog circuits are more complex than digital
Requires an ability to grasp multiple concepts simultaneously
Must be able to make appropriate simplifications and assumptions
Requires a good grasp of both modeling and technology
Have a wide range of skills - breadth (analog only is rare)
Be able to learn from failure
Be able to use simulation correctly
Simulation “truths”:---(Usage of a simulator) x (Common sense) = Constant
Simulators are only as good as the models and the knowledge of those models by
the designer
Simulators are only good if you already know the answers
Skills Required for Analog IC Design
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Complexity as a Function of the Number of Transistors
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Technology Impact On Analog IC Design
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Moore’s law: The minimum feature size
tends to decrease by a approx. factor
of 1/ 2 every three years.
Semiconductor Industry Association roadmap for CMOS
Trends in CMOS Technology
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Technology Speed: Figure of Merit vs. Time:
Trends in IC Technology
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A steeper ramp for the IC design development is required for every new generation of technology
IC Design Development Time
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The good:
Smaller geometries, Smaller parasitics, Higher transconductance, Higher
bandwidths
The bad:
• Reduced voltages, Smaller channel resistances (lower gain),More
nonlinearity, Deviation from square-law behavior
The ugly:
• Increased substrate noise in mixed signal applications, Increased 1/f
noise below 0.25µm CMOS, Threshold voltages are not scaling with
power supply, Suitable models for analog design not available
Technology impact on IC Design
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Threshold voltages and power supply
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Frequency Performance based on Scaling
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Innovation in Analog IC Design
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Technology-Driven versus Application-Driven Innovation
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Application driven circuit innovation
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• Scramble to develop new tools
• Complexity is increasing with each new
scaling generation
• Need more trained and skilled circuit
designers
Results:
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Signal Bandwidths versus Application
Analog Signal Processing
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Signal Bandwidths versus Technology
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There are established fields of application:
• Digital-analog and analog-digital conversion
• Disk drive controllers-circuit which allows the CPU to communicate with a hard
disk, floppy disk or other kind of disk drive
• Modems , filters---A modem is a device that modulates an analogue carrier
signal to encode digital information, and also demodulates such a carrier signal
to decode the transmitted information. The goal is to produce a signal that can
be transmitted easily and decoded to reproduce the original digital data
Analog IC Design has Reached Maturity
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• Codecs---A codec is a device or program capable of
performing encoding and decoding on a digital data stream or
signal.
• Bandgap reference
• Analog phase locked loops
• DC-DC conversion
• Buffers
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Regarding analog circuits:
“If it can be done economically by digital,
don’t use analog.”
Existing philosophy
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Analog finds applications where speed, area, or power have advantages over a digital approach.
Consequently
Eggshell Analogy of Analog IC Design (Paul Gray)
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Key issues:
• Analog/Digital mix is application
dependent Not scaling driven
•Driven by system requirements for
programmability/adaptability/testability/desig
nability
Analog Signal Processing versus Digital Signal Processing in VLSI
Application Areas of Analog IC Design
• There are two major areas of analog IC design:
• • Restituitive - performance oriented (speed, accuracy, power, area)
Classical analog circuit and systems design
• Cognitive - function oriented (adaptable, massively parallel)
A newly growing area inspired by biological systems
Analog VLSI (An oxymoron):
• Combination of analog circuits and VLSI
philosophies
Many similarities between analog circuits and biological systems
• Scalability
• Nonlinearity
• Adaptability
Neuromorphic analog VLSI
• Use of biological systems to inspire circuit design such as smart sensors and imagers
Smart autonomous systems
• Self-guided vehicles (Mars lander)
• Industrial cleanup in a hazardous environment
Sensorimotor feedback
• Self contained systems with sensor input, motor output
What is the Future of Analog IC Design?
• • Technology will require more creative circuit solutions in
order to achieve desired performance
• • Analog circuits will continue to be a part of large VLSI
digital systems
• • Interference and noise will become even more serious as
the chip complexity increases
• • Packaging will be an important issue and offers some
interesting solutions
• • Analog circuits will always be at the cutting edge of
performance
• • Analog designer must also be both a circuit and systems designer and must know:
-Technology and modeling
-Analog circuit design
-VLSI digital design
-System application concepts
• • There will be no significantly new and different technologies - innovation will combine new applications with existing or improved technologies
• • Semicustom methodology will eventually evolve with
CAD tools that will allow:
- Design capture and reuse
- Quick extraction of model parameters from new
technology
- Test design
- Automated design and layout of simple analog circuits
NOTATION, SYMBOLOGY, AND TERMINOLOGY
Example:
MOS Transistor Symbols
Other Schematic Symbols
SUMMARY
• • Analog IC design combines a function or application with
IC technology for a successful solution.
• • Analog IC design consists of three major steps:
• 1.) Electrical design , Topology, W/L values, and dc currents
• 2.) Physical design (Layout)
• 3.) Test design (Testing)
• • Analog designers must be flexible and have a skill set that
allows one to simplify and understand a complex problem
• • Analog IC design is driven by improving technologies
rather than new technologies.
• • Analog IC design has reached maturity and is here to stay.
• • The appropriate philosophy is “If it can be done
economically by digital, don’t use analog”.
• • As a result of the above, analog finds applications where
speed, area, or power have advantages over a digital
approach.
• • Deep-submicron technologies will offer severe challenges
to the creativity of the analog designer.
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END