ptarmigan

Sorry if you've already clarified, but is this meant to replace or augment traditional SPICE simulators? I remember Ken Kundert mentioned that, even with the improvements of Spectre over SPICE-based simulators, it took things like SpectreRF's oscillator phase noise modeling to get analog designers to consider changing their ways. Their steadfast use of SPICE is "a form of Stockholm Syndrome," in his own words.

Do you think such an approach could extend to the final verification stage of a large post-extraction chip? My impression is that speedups are most sorely needed in this final sign off phase where the number of nodes explodes with parasitic R's and C's, especially in modern technologies. Simulation times in weeks seem necessary now for sufficient verification accuracy of analog/mixed signal chips.

More as background to ADI's acquisition of Linear Tech, but often these acquisitions come down to one chipmaker's desire to offer a full system. Take for instance Analog Devices' RF converters: https://www.analog.com/en/applications/technology/rf-convert...

These chips cost hundreds or thousands of dollars and are meant for base stations. Analog Devices wants to get a contract with Nokia or anyone else and then also be able to sell the LDOs, PLLs, and clock devices that go along with it (https://www.analog.com/en/products/AD9213.html#product-tools). Linear Tech was the leader in power and the name is still used for new power products under the "Power by Linear" name with ADI. Hittite offers a number of RF chips. If you're paying $1k for a data converter, what's an extra $50 for all the analog/RF support circuitry? They may even throw it in for free. If you have a complex system with analog/RF/digital circuitry, offering a full reference design with other parts from your own catalog is a great way to ensure that those parts are used.

To add a bit of context for anyone interested, there are some interesting reasons why switched capacitor circuits are powerful in integrated CMOS design. In terms of matching, the choice between resistors and capacitors is due to size and matching. Large values of resistance require large resistors or can be implemented with smaller capacitors, switches, and a clock (https://en.wikipedia.org/wiki/Switched_capacitor#The_switche...). Resistance values which would be prohibitively large to get with a resistor in modern processes can be achieved with switched capacitors. Additionally (and more importantly), capacitors can have better matching due to their geometries. If we want a gain of 10 on-chip, switched capacitor circuits are very well suited. Switched capacitor circuits obviously can't be used everywhere (need a clock, not continuous time), but they provide some good advantages.

Considering a resistor as a sheet with a length and width, increasing the length or decreasing the width will increase the resistance. A large resistance means a long and thin material. For a capacitor, we just care about the overall area of the plates and normally use squares. There are variations to the dimensions generated for both of these shapes. The long, thin resistor is more sensitive to these absolute changes in its width and thus the best matching is reduced. The absolute values of both resistors and capacitors are poor, but the matching of capacitors can be as good as 0.1% (enough for 10-bits of accuracy). http://ims.unipv.it/Courses/download/AIC/Layout03.pdf

There are a few switched-capacitor ICs, though they're more for boutique applications at this point. https://www.analog.com/media/en/technical-documentation/data...

Yep, that's the one.

The classic textbook for analog transistor-level design is Analysis and Design of Analog ICs by Gray and Meyer (mentioned in a footnote). It assumes a strong background and goes more for comprehension than building insight so I wouldn't recommend it initially. For actual design, Behzad Razavi's books are great to gain insight. I really enjoy his pedagogical approach. Agarwal and Lang have a good sophomore/junior level book as do Sedra and Smith (Razavi's microelectronics book is also good).

Art of Electronics always deserves a mention in circuits book discussions. The former books all take more rigorous approaches to things while AoE focuses strongly on practical insight. It's less of a textbook than the others (fewer equations) but includes many real examples of circuits, from simple to very complex.