The paper deals with a multiple fault diagnosis of DC transistor circuits with limited accessible terminals for measurements. An algorithm for identifying faulty elements and evaluating their parameters is proposed. The method belongs to the category of simulation before test methods. The dictionary is generated on the basis of the families of characteristics expressing voltages at test nodes in terms of circuit parameters. To build the fault dictionary the n-dimensional surfaces are approximated by means of section-wise piecewise-linear functions (SPLF). The faulty parameters are identified using the patterns stored in the fault dictionary, the measured voltages at the test nodes and simple computations. The approach is described in detail for a double and triple fault diagnosis. Two numerical examples illustrate the proposed method.

The paper deals with circuits, composed of bipolar transistors, diodes, resistors and independent voltage sources, having multiple DC solutions. An algorithm for tracing temperature characteristics, expressing the output signal in terms of the chip temperature, is developed. It is based on the efficient method for finding all the DC solutions sketched in this paper. The algorithm gives complete characteristics which are multivalued and usually composed of disconnected branches. On the other hand the characteristics provided by SPICE are fragmentary, lose some branches or exhibit apparent hysteresis.