D-A converter based variation analysis for analog layout design

For analog circuits, the current source is one of the most essential functions, and variation of its characteristic seriously influences to the accuracy of the performance. This paper presents a new methodology for analyzing the layout dependency of the variation of the current source transistor. We employ a current-driven D-A converter to investigate the dependency of the current source upon the relative accuracy and the ¿. We implemented the D-A converts with various layout structures into TEG(Test Element Group), and evaluated them. The analysis convinced us that the diffusion sharing and gate folding significantly influence to the variation of ¿ and relative accuracy.