A section
You're new to this field, with only a general understanding of PMOS/NMOS/BJTs, and you're not very clear on the characteristics of various devices. You don't have much idea about what kind of circuits to design, and your circuit diagrams are mainly based on articles in domestic journals or existing circuits in textbooks. You always feel that what they say makes sense. The circuits you make are mainly small-scale modules, doing simulations of differential op-amps or bandgap references, and you're calculating to publish papers, afraid of not having enough papers to publish. In general, you're still intimidated by op-amps. You think SPICE is a very difficult and strange thing to use.
Second section
You begin to understand circuit design, spending your days frantically calculating on scratch paper while holding a textbook. You also frequently start mentioning technical parameters like Vdsat, lambda, early voltage, GWB, and ft. Sometimes the circuit seems close to the hand-calculated result, while other times the difference is significant. You also begin to pay attention to variations in voltage, temperature, and manufacturing processes, such as low-voltage, low-power systems, or ultra-high-speed, high-precision technologies, occasionally adding your own thoughts. You start planning tapeout when designing circuits, although tapeout still seems quite distant. During this stage, you find SPICE powerful, but often get frustrated by incorrect AC simulation results.
Three sections
You've been struggling with PVT for a while now, but overall you haven't had many successful design experiences. You find designing truly usable circuits incredibly difficult, and you're eager to build your confidence, but you don't know how. You've started reading JSSC papers or doctoral dissertations, but you feel that what they say is one thing, and the actual chip is quite another. You feel that metrics like Vdsat are not precise enough, and the simulator's default settings don't meet your requirements, so you try adjusting simulator parameters or even switching simulators, but the results are still inconsistent. You go to forums hoping to get guidance from experts, but their explanations are vague, and what they say is sometimes right and sometimes wrong. At this stage, you feel that while SPICE is good, its help manual is too unclear.
Four sections
You've experienced significant chip fabrication failures, and you know that creating a good circuit requires meticulous attention to detail and rigorous inspection of every aspect. You've discovered numerous unforeseen problems during the design process, and a complete grasp of every facet is necessary for a successful circuit. So, you begin systematically relearning the textbooks you sold upon graduating from university. You carefully review all available resources, hoping to find more insightful ideas. You clearly understand the circuit specifications and performance you need to achieve, and you know that circuit design inherently involves many reasonable trade-offs. However, you're unsure how to determine what constitutes "reasonable," or how to choose the best compromises between different specifications. You feel that designing a properly functioning circuit is incredibly difficult; you don't believe anyone in the world can achieve what they claim, because even someone as intelligent as you feels overwhelmed by such complex choices—how could they possibly succeed? During this stage, you feel that SPICE's functionality is still too limited, and you often stare blankly at "timestep too small" error messages. Occasionally, you even create massive simulation files that crash everyone and the computer.
Five-stage
You feel that many competitors' products are not so great, and you've started to have a relatively familiar design methodology. However, you don't know how to further optimize the tools at hand. You've used some pre-written scripting languages, but often when you encounter many problems, you can't remember to use awk or perl to solve them. You start to consume a lot of server simulation time, believing that through a lot of simulations, you can clearly adjust your designed modules to the appropriate state. Sometimes you feel that circuit design is simply too boring, and if it really doesn't work, you consider whether you should give up. At this stage, you think that Spice is good, but it's still far inferior to the FastSpice series of simulators; you start to distrust AC simulation and replace it with a lot of transient simulations.
Six Dan
You begin to understand that in this world, there is only the most suitable design, not the best design. You start to have your own design methodology, and you tend to favor one or two simulation tools, using them proficiently to evaluate your designs. You begin to consider PVT variations in your designs, understanding the evolution of a circuit from its inception to the present, and can tailor it for different applications. You start to focus on power consumption and area, and some of your tape-out chips begin to meet product requirements. However, sometimes you still don't fully understand the design methodologies of complex systems and make some foolish mistakes that lead to disastrous consequences. When you start reading JSSC, you don't just pick and choose a couple of articles; perhaps using JSSC as toilet reading material is a good choice for you. At this stage, you realize that SPICE is a great tool, knowing how to perform reasonable simulations for accuracy and speed in SPICE and making the most appropriate choice at any time.
Seven Dan
You begin to truly understand the essence of analog circuit design, developing unique perspectives and experience for both high-precision and high-speed systems. You can compromise on different module specifications at the system level to achieve the best performance. You'll understand a potential market and begin defining your own products, knowing that with the right approach, your designs will be highly competitive. You can confidently divide the entire circuit's functions and specifications from start to finish, understanding the impact of every technical detail and their trade-offs on your product. You begin to focus on design reliability. At this stage, you find Spice a very useful tool and enjoy Monte Carlo simulations, but you still frequently complain about the slow server, even though you often run simulations late at night.
Eight Dan
At this point, successfully creating a chip is commonplace for you, like a seasoned driver stopping at red lights and proceeding at green lights. Product design is almost unconscious for you. You no longer need to constantly adjust parameters and optimize based on simulation results; often, a small amount of simulation is enough to complete the design of a module. You can clearly sense whether a circuit module with a certain specification is technically possible or impossible. You don't need to worry about the noise figure, signal-to-noise ratio, or distortion of a specific module. You only need to know that it can be designed; more detailed technical specifications are meaningless to you. You start to feel that the things on JSSC are just filler, sometimes even considering JSSC unsuitable as toilet paper (too thin and brittle). You think Spice is okay to use occasionally, but it's unreliable; often, checking the operating point is enough.
9th Dan
By this point, you have an encyclopedic understanding of many circuits and can anticipate the next wave of technological development. You might only run simulations a few times a year, or you might spend several years on a single simulation. You rarely draw circuit diagrams; most of the time you're playing golf or fishing on some island in the Pacific. Aside from occasionally joining in at ISSCC, you never discuss circuit-related matters with others because you know no one would understand.
