Without sophisticated design automation techniques, the increasing complexity of custom MOS circuits requires long design cycles and large investments. Usually only a few parts of each type of custom MOS circuit are required, and the design cost becomes a significant portion of the cost of the manufactured parts. These facts prohibit many companies from using custom MOS circuits in their products. Design automation applied to custom MOS circuit design significantly lowers the total design cost by shortening the design cycle, reducing labor, and allowing error free designs to be produced before being manufactured. This makes possible the use of custom MOS circuits, even when only a few parts are required.