A topology-dependent expert system for DC design of a self-biased single transistor stage was developed and tested. The test case system was implemented in Turbo Prolog and was run on an XT-compatible personal computer. The rule-based system includes four groups of rules: heuristic, general network, topology-dependent network, and default rules. It is shown that the expert system mimics the human design procedure and can handle mathematically ill-defined design problems. A main inherent feature of the proposed expert system is its ability to produce a design solution for any given combination of non-conflicting input specifications.