“Analog IC Design – Essential Insights” – Prof. Seung-Tak Ryu (KAIST)

Great analog designers are known for their intuition — the ability to predict circuit behaviour, make smart trade-offs, and identify issues before they appear. Intuition comes from a deep grasp of fundamentals, not from brute-force simulations. Among analog building blocks, the operational amplifier (opamp) stands as the most representative example, encompassing nearly all essential design challenges, including gain, bandwidth, feedback, stability, frequency and transient response, noise, and matching.

This course focuses on building intuitive understanding, giving engineers the insight and confidence to design, analyse, and optimize analog circuits with clarity and efficiency. It offers a structured, practical exploration of analog IC design centred around operational amplifiers, covering core opamp principles and advancing to sophisticated switched-capacitor (SC) circuit techniques. Practical design projects are integrated throughout, allowing participants to apply theory directly to real-world analog circuit implementations.

The course begins by exploring fundamental opamp architectures, focusing on telescopic and folded-cascode amplifiers. Key topics include DC gain, input/output common-mode range (CMR), biasing strategies for wide CMR, and common-mode feedback (CMFB) in fully-differential designs. Essential frequency response aspects such as bandwidth and stability are also covered.

Next, participants explore two-stage opamp architectures and examine how Miller compensation techniques influence frequency response to ensure stability. The course also introduces the concept of unwanted positive zero and methods to mitigate its impact.

The focus then shifts to transient response, covering concepts such as linear settling and slew-rate limitations. This section also introduces output stage architectures, including the common-source configured class-AB design (Huijsing amplifier). The course then expands into advanced amplifier structures, discussing topics like gain boosting, nested Miller, and multipath approaches.

With this theoretical groundwork in place, hands-on design examples are introduced, including fully-differential folded-cascode and/or two-stage opamps. Participants will evaluate biasing, gain, stability of both the signal path and CMFB paths, transient behaviour, and testbench configuration.

After exploring continuous-time circuit design, the course progresses to discrete-time analog design, beginning with the principle of charge conservation in switched-capacitor (SC) networks. These lectures cover the operation of SC gain stages, sample-and-hold circuits, multiplying DACs (MDACs), SC integrators, and CMFB mechanisms in SC systems. The course also examines recent dynamic amplifier architectures, such as the Ring Amplifier (Ringamp) and Floating Inverter Amplifier (FIA), highlighting their design principles and emerging trends.

The course concludes with a second design project focused on switched-capacitor gain amplifiers. Flip-around and/or charge redistribution structures are explored in detail, including an analysis of loop gain, stability in both signal and CMFB paths, and settling behaviour.

To reinforce the material covered in each lecture, participants will have the option to complete homework assignments that extend their learning through practical application. These exercises may include SPICE simulations to explore circuit behaviour or analytical problems focused on design calculations. Engaging with these tasks helps deepen understanding and provides hands-on experience beyond the core lectures.

This course is tailored for engineers working in analog circuit design who want to deepen their expertise and cultivate strong intuitive skills, as well as for professionals seeking a broader understanding of data converter fundamentals. Focusing on practical applications, it empowers participants with the insight and confidence to tackle real-world analog circuit challenges.