Feedback driven backtrace of analog signals and its application to circuit verification and test

This paper describes a new approach for backtracing analog signals in a circuit. The process of backtracing involves finding the input signal to an analog circuit, from knowledge of its input-output behavior and the desired output signal. While previous approaches rely on the transformation of nodal equations of the circuit to accomplish backtrace, the proposed approach derives the input signal using feedback and forward simulation of a modified circuit. Hence any commercial circuit simulator can be used to the implement the backtrace function. DC convergence conditions for the proposed backtrace approach are derived and it is shown that in the absence of hard nonlinearities, the proposed approach converges to the final solution at a quadratic rate. Application of the backtrace approach to DC verification and test of analog circuits is discussed.