New Aspects of Fault Diagnosis of Nonlinear Analog Circuits

The paper is focused on nonlinear analog circuits, with the special attention paid to circuits comprising bipolar and MOS transistors manufactured in micrometer and submicrometer technology. The problem of fault diagnosis of this class of circuits is discussed, including locating faulty elements and evaluating their parameters. The paper deals with multiple parametric fault diagnosis using the simulation after test approach as well as detection and location of single catastrophic faults, using the simulation before test approach. The discussed methods are based on diagnostic test, leading to a system of nonlinear algebraic type equations, which are not given in explicit analytical form. An important and new aspect of the fault diagnosis is finding multiple solutions of the test equation, i.e. several sets of the parameters values that meet the test. Another new problems in this area are global fault diagnosis of technological parameters in CMOS circuits fabricated in submicrometer technology and testing the circuits  having multiple DC operating points. To solve these problems several methods have been recently developed, which employ  different concepts and mathematical tools of nonlinear analysis. In this paper they are sketched and illustrated.  All the discussed methods are based on the homotopy (continuation) idea. It is shown that various versions of homotopy and combinations  of the homotopy with some other mathematical algorithms lead to very powerful tools for fault diagnosis of nonlinear analog circuits.  To trace the homotopy path which allows finding multiple solutions, the simplicial method, the restart method, the theory of linear complementarity problem and Lemke's algorithm are employed. For illustration four numerical examples are given

A SPICE-Oriented Method for Finding Multiple DC Solutions in Nonlinear Circuits

Finding multiple operating points of nonlinear circuits is a fundamental issue in electronic circuit analysis and design. Methods that guarantee finding all DC solutions are very time-consuming and can be used to analyze only rather small-sized circuits. On the other hand, there exist approaches that can find multiple operating points, but they do not guarantee finding all solutions. The methods are less time-consuming, do not require much computing power, and allow for analyzing more complex circuits. This paper proposes an efficient method for determining multiple and, in most cases, all DC solutions. The approach uses a deflation technique, and the SPICE simulator is applied to the calculations. For this purpose, the original nonlinear circuit during the computational process was modified appropriately after successive solutions were determined. The method was verified on benchmark nonlinear circuits from the literature, made in various technologies and using various models. The results of the DC analysis of several circuits are provided

Editorial - Electronic Circuits Testing

We greatly appreciate the opportunity to highlight the topic of electronic circuits testing by the International Journal of Electronics and Telecommunications. Imperfections in the manufacturing process requires testing of hardware-implemented circuits and their components. The increasing complexity of such systems makes this issue more and more demanding. The main objective of testing is to distinguish between good and faulty ones. This objective can be achieved in several ways, e.g. by functional or structural testing. Either analog or digital, fault detection or location in electronic systems is usually performed by analysis of measurements results acquired from a limited number of inputs and outputs. This problem becomes near critical with the advent VLSI and ULSI components. For more than five decades, the subject of fault location in analog and mixed-signal circuits has been of interest to researchers. In recent ten years this interest has been intensified significantly. The device and voltage scaling scenarios for present and future nanometer CMOS technologies cause that the attention will shift to testing defects that did not exist before or that were not relevant in the past...

Diagnosis of Soft Spot Short Defects in Analog Circuits Considering the Thermal Behaviour of the Chip

The paper deals with fault diagnosis of nonlinear analogue integrated circuits. Soft spot short defects are analysed taking into account variations of the circuit parameters due to physical imperfections as well as self-heating of the chip. A method enabling to detect, locate and estimate the value of a spot defect has been developed. For this purpose an appropriate objective function was minimized using an optimization procedure based on the Fibonacci method. The proposed approach exploits DC measurements in the test phase, performed at a limited number of accessible points. For illustration three numerical examples are given

Multiple Soft Fault Diagnosis of Bjt Circuits

This paper deals with multiple soft fault diagnosis of nonlinear analog circuits comprising bipolar transistors characterized by the Ebers-Moll model. Resistances of the circuit and beta forward factor of a transistor are considered as potentially faulty parameters. The proposed diagnostic method exploits a strongly nonlinear set of algebraic type equations, which may possess multiple solutions, and is capable of finding different sets of the parameters values which meet the diagnostic test. The equations are written on the basis of node analysis and include DC voltages measured at accessible nodes, as well as some measured currents. The unknown variables are node voltages and the parameters which are considered as potentially faulty. The number of these parameters is larger than the number of the accessible nodes. To solve the set of equations the block relaxation method is used with different assignments of the variables to the blocks. Next, the solutions are corrected using the Newton-Raphson algorithm. As a result, one or more sets of the parameters values which satisfy the diagnostic test are obtained. The proposed approach is illustrated with a numerical example

Multiple soft fault diagnosis of analog circuits using restart homotopy method

This paper offers a method for multiple soft fault diagnosis of nonlinear circuits containing bipolar and MOS transistors. The method enables us to locate faulty elements and evaluate their parameters, using a nonlinear algebraic type test equation which may possess several solutions. To find the solutions the homotopy concept is applied and a homotopy differential equation written. Next the terminal value problem is formulated and solved using the restart approach. A numerical example illustrates the proposed approach