An optimization-based approach to efficient design of analog circuits

Abstract: Traditional design methods for analog circuits are based on rules-of-thumbs, experience, and trial-and-error approaches involving the use of circuit simulators. It is an unstructured process, which is time-consuming, error prone, and requires the attention of a skilled analog designer. This situation calls for design methodologies thatare more efficient.We have developed an efficient approach and corresponding tools that address these issues. A computer-aided design tool for design of large analog circuits with low level of human intervention has been developed. The tool combines efficient performance measure evaluation and optimization methods to determine the device sizes and generate layouts for analog circuits. Large analog circuits with about 200 devices have been designed. The circuits are optimized with respect to, e.g., power consumption, and subject to a large number of performance requirements. All performance measures are automatically derived, which reduces the probability of introducing errors.Experimental results indicate that our approach can be used to design robust highperformance analog circuits with improved performance compared to manual approaches. Furthermore, the computer-aided tool decreases both the overall design time and the time required of a skilled designer.We have developed a technique that derives the performance equations directly from the circuit schematics as well as techniques for efficient evaluation of the equations. This approach reduces the risk of introducing errors and enables the use of accurate device models, i.e., high-accuracy equations without approximations are obtained.In fully differential circuits, common-mode stabilization is required. Even though a multitude of common-mode feedback circuits have been presented in the literature, the performance requirements for these circuits are rarely fully explained. Here, the common-mode feedback design problem is addressed to gain design insights. A Volterra series model is used to analyze the distortion terms caused by the use of a common-mode feedback. From this analysis, the DC gain, bandwidth, and stability requirements of the common-mode loop are discussed.