This paper deals with diagnosis of soft faults for analog circuits in simulation after test approach. Simple approximate pole/zero expressions, depending only on the most significant parameters, are computed. The parameters values for the soft faults in linear circuits are identified employing these expressions and gain vs. frequency characteristics. This approach uses simpler equations and proves a higher power to identify the faulty components than other approaches.

Keywords: Analog circuits, Fault diagnosis, Approximate symbolic pole/zero expressions, Simulation after test