A design methodology for analog circuit blocks is proposed which combines circuit knowledge and high-level general-purpose math packages with CAD simulation tools. The proposed flow of the design of a complex analog or mixed-signal system starts with a conceptual phase setting performance goals for each block, Followed by an exploration phase based on analytical descriptions resulting in the selection of a performance point in the design space and an implementation phase resulting in the sizing of the transistors in each block. The final phase of the electrical design is verification, optimization and design centering in SPICE using foundry-provided process data. It is shown that numerical optimization available in some SPICE offerings such as Eldo deliver a design that not only meets specifications but delivers optimal performance for a selected objective within given constraints