The main objective of this work is to improve the design flow of analog and mixed signal integrated circuits. Purely digital systems profit from standardized tools and methods which allow automatic synthesis. In the analog domain, automatic synthesis has probably no sense and efforts must be done towards developing consistent and coherent CAD (Computer Aided Design) methods and tools. The main idea is to re-use the accumulated design knowledge which could be illustrated by the IP (Intellectual Property) concept. In this paper, we give our experience on the following aspects: content of an analog IP, IP-based library and its integration in the system design flow, applied on a specific example.