| The integration of high-performance analog and digital circuits leads to an increasing need of new tools compatible for both the digital and analog parts. Unfortunately, the low acceptance of CAD tools in the analog domain presents a serious bottleneck to the fast realization of mixed-signal systems. Due to a higher sensitivity of the electrical performance to layout details, analog designs are much more complicated than digital ones. Process and temperature variations can introduce severe mismatches in devices that are designed to behave identically. These undesirable effects can be alleviated by a symmetric layout. Matching and symmetry in placement and routing in analog circuits are thus of immense importance.;In this thesis, we will present an effective layout method for analog circuits. We consider symmetry constraint, common centroid constraint, device merging and device clustering during the placement step. Symmetric routing will then be performed. In order to have successful routing, we will perform analog-based routability-driven adjustment during the placement process, taking into account for analog circuits that wires are not preferred to be layout on top of active devices. All these concepts were put together in our tool. Experimental results show that we can generate quality analog layout within minutes of time that passes the design rule check, layout-schematic verification and the simulation results are comparable to those of manual design, while a manual design will take a designer a couple of days to generate. |
