| Category | Difficulty |
|---|---|
| HW | 5 |
| Projects | 8 |
This class focuses on transistor-level analog and mixed-signal integrated circuit design providing hands-on experience with sampling circuits, digital-to-analog converters (DACs), and analog-to-digital converters (ADCs).
The course will begin with basic concepts of data conversion systems. Switched capacitor circuits are introduced as a very common class of discrete-time circuits and basic building blocks of sampling circuits, DACs, and ADCs. Fully-differential amplifiers are reviewed and further developed as these are crucial building blocks in many analog and mixed-signal systems. DACs are introduced and related topics such as mismatch are covered in depth. In the remainder of the course ADCs are extensively discussed, including the analog comparator as a basic building block and numerous ADC architectures. The bulk of the course will focus on hands-on data converter design through the course projects.
Students should have taken 18-623 or a similar course focusing on transistor-level analog circuit design. The course will use Cadence Virtuoso for the design projects and will assume that you've had prior exposure to the tool. The projects will involve building up your designs and testbenches from scratch, so it's very important that you've had experience with designing and verifying schematics in Virtuoso (layout experience is much less important and likely won't be part of the course).
You will also likely find it helpful to review some signal processing fundamentals as these continue to be important in 18-721, e.g. in the context of sampling circuits. Concepts like time and frequency domain representations of signals, Fourier transforms (continuous/discrete), and Laplace transforms will be helpful. If you've had prior exposure to Z-transforms that will also be helpful but not essential.
Finally, some experience with scripting, e.g. in MATLAB or Python, will be helpful for the design projects.
There will be a couple homeworks in the beginning of the semester before the focus switches to the design projects. Some of the homework will include review of important topics from 18-623 that you'll have to apply in the projects like large- and small-signal analysis of single and multiple-transistor CMOS amplifiers. It may also include some initial practice with switched-capacitor circuits that will be common throughout the course.
The projects are the main focus of the course and there are generally three of them. These are individual projects and they will likely be more open-ended than in your previous IC design classes: for each design project you're usually provided with several design target options (e.g. a high-speed option, a very low power option, and so on) to choose from. However, asides from those specifications, it'll be up to you to decide what kind of circuit to design and how to check that it works by making your own testbenches. As mentioned above since you're doing virtually all the design and verification yourself from scratch it'll be extremely helpful to have had prior exposure to design in Cadence Virtuoso so that you don't need to spend a lot of extra time learning how to use it for the first time (it should be totally sufficient if your only other experience with Virtuoso is from 18-623 or similar).
The focus of the projects is subject to change but the last of the three will very likely be an ADC. This means designing a system which takes in an analog signal (continuous in time and amplitude, usually a voltage) and converts it into a digital signal (discrete in time and amplitude). The given specifications will define your final system-level performance requirements and give you a lot of freedom to make decisions about what kind of architecture to design and what specific algorithms/circuit topologies to implement within those architectures. For example, a very common category of ADC is a successive-approximation register (SAR) converter; you might choose a SAR architecture for the project but even within that there are numerous variations for you to choose from.
Part of what makes 18-721 projects challenging is that unlike e.g. small-signal amplifiers you might have worked on in previous courses there are many crucial metrics that are more difficult to analytically predict, design for, and simulate than small-signal gain and bandwidth. This includes metrics such as settling time/slew rate, offset and mismatch, noise, and nonlinearity/distortion. Besides being hard to analyze by hand these can also be very time consuming to simulate (e.g. on the order of hours), so it's important not to leave things for the last minute since you might just not have enough time. You should plan to budget time to figuring out exactly how you'll calculate the metrics required for the project since some of them are difficult to calculate directly with Virtuoso.
- Course Description
- Course textbook: Analog Integrated Circuit Design, 2nd Edition. This is one of the few available references for CMOS data converter design written in the format of a typical textbook.
- Additional reference: Design of Analog CMOS Integrated Circuits, Second Edition. This is a very readable, well-written textbook that'll be very helpful for reviewing fundamental topics, especially analysis of single/multiple transistor linear amplifiers. This textbook also has useful coverage of topics that may be new to you in 18-721 such as noise and switched-capacitor circuits.
- Additional reference: Analysis and Design of Analog CMOS Integrated Circuits. This is a very rigorous and in-depth treatment of analog IC design fundamentals. It's less approachable than Razavi's text but useful as a reference to help fill in some details.