Strategies and Routines in Analog Design

Abstract

This paper addresses fundamental aspects of analog design automation. Rather than following the present trends of basing the development of design automation tools on the existing expert knowledge of circuit topologies, proven circuit implementations and application examples, it emphasizes the need for the development of strategies and routines for generating specific solutions for design problems, starting from a definition of the required behaviour of a basic signal-processing function. The proposed design approach differs from the traditional approach in that it explicitly takes the signal information as a starting point for setting up performance requirements. As a prerequisite for true design automation, it thereby attempts to explicitly formulate all steps required to find adequate solutions, formulated in terms of information processing fidelity. It isolates the various performance aspects, tries to find optimization strategies for each of them individually, and subsequently, tries to find strategies to minimize their interaction. It concentrates first on three essential limitations of all physical systems: speed, noise and power, the three elements of Shannon’s formula for channel capacity. By attaching behavioral models to active devices with respect to each of these aspects in combination with the above mentioned strategies, one can quickly decide on the fundamental feasibility of a function, given a certain implementation technology. The strategies refer to circuit topology generation as well as to modification of the behaviour by applying error-reduction techniques in several subsequent hierarchical steps. During this process, other performance requirements such as those with respect to offsets, accuracy, non-linearity, etc., are taken into account. The routines refer to calculation methods needed for quick analysis and to the tools for the final verification.