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A new approach for the multiple fault location in linear analog circuits is proposed. It presents the characteristic of using classical numerical procedures together with symbolic analysis techniques, which result particularly useful in the parametric fault diagnosis field. The proposed approach is based on the k-fault hypothesis and is provided with efficient algorithms for fault location also in the case of low testability circuits. The developed algorithms have been used for realizing a software package prototype which implements a fully automated system for the fault location in linear analog circuits of moderate size. Index Terms - Analog circuits, fault diagnosis, symbolic techniques.

The use of computer based tools in electrical engineering courses should be always accompanied with the possibility to gain an insight into the circuit properties. This can be achieved by using a computer program which combines symbolic and numerical simulation capabilities. This approach in providing students of automatic analysis tools is more significant and complete. Therefore the program SAPWIN has been developed by the authors. This program includes the capability of generating the complete or approximate symbolic (fully or partially) output expressions of analog linear circuits and their graphical manipulation. In addition, it permits to obtain Spice netlist of a circuit, in order to work in a complete, self-sufficient environment, useful for both teachers and students. The program can be used 'as is,' like an useful tool during basic electrical sciences or network theory lessons, or like a starting platform on which to develop further application that requires symbolic formulas, eventually directly operating on the program code. The positive outcome of the first release of Sapwin, here presented, urged us to work on a completely renewed one, which will be ready as soon as possible. Index Terms--Computer aided design (CAD), electrical engineering, symbolic analysis.