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This brief deals with soft-fault diagnosis of analog circuits. Both ac and dc linear circuits, as well as dc nonlinear circuits with limited number of test points are considered and the presence of component tolerances is taken into account. An approach using the linear-programming concept and the simplex method is developed. Contrary to other methods which use optimization techniques for diagnosis, no optimization process for evaluating the parameter deviations is performed. In fact, only phase 1 of the simplex method is applied to check the existence of a feasible solution. It enables us to state whether the actual parameters are within tolerance ranges or some components are faulty. Identification of the faulty elements is achieved using a similar idea. Three numerical examples illustrate this approach.