A Nullator-Norator-based Analogue Circuit DC-Test Generation Approach

1 Introduction For analogue circuits the development of automatic test generation techniques is still a subject of In this paper we propose a fault-oriented technique for generating DC-tests for nonlinear analogue circuits. At the time being the circuits to be considered have single inputs and single outputs. An extension to circuits with multiple inputs and outputs is still under investigation. The proposed technique is based on a test generation model that makes use of the »singular« network elements nullator and norator [3, 4]. Nullators and norators are network elements with two terminals. Both the current and the voltage of a nullator are equal to zero. For a norator, however, its current and its voltage may have any value. When nullators and norators are used in a network to be simulated by means of a usual electric simulator then these elements have to be used necessarily in pairs, i. e. as a two-port (Figure 1). Such a nullator-norator two-port, also referred as to a nullor, can also be described by an interconnection of controlled sources or, easier, by means of a VHDL-AMS model. An analogue circuit is regarded as a two-port. W. l. o. g. we consider voltages as to be the quantities for test input and test output. In Figure 2 an ideal voltage source is connected to the lhs port, i.e., v 1 = v in. Since the output load can be considered as a part of the circuit the test output quantity is the open circuit voltage at port 2, i.e., v 2 = v out and i 2 = 0. The analogue circuit described as a two-port in Figure 2 is connected with a nullator and a norator in the following way (cf. Figure 3): The voltage source of the input port is substituted by a norator. A series connection of a nullator with an independent voltage source is connected to the output port. If the simulated value for voltage v 2 in Figure 2 is now taken as the value v out of the voltage source on the rhs then the voltage over the norator will be v 1 = v in. By applying the substitution theorem of the network theory [19, 20] it can be shown, that each solution Figure 1: Norator-nullator two-port (Nullor) Figure 2: Two-port model of the analogue circuit