Analog and mixed-signal IC design and design methodologies

During the past decades, we have witnessed a progressive substitution of analog-based solutions by digital ones, in parallel with the continuous evolution of technological processes, especially CMOS, towards deep submicron technologies. This technological shrinkage has enabled the integration of more and more functionalities on a single chip, with the consequent reduction in area, cost and power consumption; therefore, fueling, for instance, the information technology revolution. Although analog circuitry has been, in most cases, relegated to the interface between the digital processing subsystems and the analog world, e.g., the physical channel in communication systems, the trend towards higher system integration is also reaching the analog and mixed-signal circuitry. Nowadays, it is not uncommon to integrate complex digital subsystems like microprocessors, memories, etc., with analog and mixed-signal blocks, RF blocks and even sensors onto the same substrate, constituting what is already commonly known as a System-on-Chip (SoC). New applications and higher system functionalities are continuously demanding more aggressive specifications of analog and mixed-signal circuits in hostile environments (i.e., continuous decrease of supply voltages, substrate coupling with noisy signals, etc.) and it is usually the performance of this circuitry which limits the performance of the overall system. Demands also extend to design methodologies and tools for analog and mixed-signal subsystems, traditionally much less developed than for digital circuits. The comparatively low number of CAD tools and methods may dramatically increase the design time and cost of a SoC product, and it may eventually be responsible for the loss of the market window. In this context, the extension of the scope of Integration—the VLSI journal to cover the analog and mixed-signal field was a natural evolution. Hopefully, this Special Issue inaugurates a permanent presence of papers on analog and mixed-signal design. The call-for-papers had a wide acceptance and numerous submissions were received. All papers were subject to peer-review by international experts and it was a tough work to select those which would be included in the limited number of pages of the special issue. I hope that you will enjoy these papers. Regarding the organization of the issue, six papers have been selected dealing with significant aspects of design and design methodologies of analog and mixed-signal ICs. Operational amplifiers are the most common block in analog design. Analog designers have to face continuously decreasing supply voltages due to the scaling down towards deep submicron IC technologies. However, transistor threshold voltages are not decreasing at …