Soft fault diagnosis of non-linear circuits having multiple DC solutions

This study deals with a single soft fault diagnosis of non-linear circuits having multiple DC solutions. The key problem of the diagnosis is arranging a measurement test. Creation of the test for the above-defined class of circuits is discussed in detail. It is assumed that only input and output terminals are accessible in the circuit. The test is created based on some single-valued input or transfer characteristics traced in a modified circuit. The modification does not disturb the integrity of the circuit and is realised by connecting some components to the accessible terminals. A very fast method for tracing the characteristics is developed. Having appropriate characteristics several values of the exciting voltage are chosen and the corresponding values of voltage or current defined by the characteristic are measured in the course of testing. The method for arranging the measurement test is illustrated using four non-linear circuits having multiple DC solutions and three of them were built in bipolar and complementary metal-oxide-semiconductor (CMOS) technology. One of the circuits is comprehensibly diagnosed using a method for detecting, locating, and estimating values of different faulty parameters exploiting the proposed test.