An efficient approach to the computation of analytic, pseudo analytic sensitivities and noise in an APL general purpose CAD program

Abstract

An approach to sensitivity computation has been implemented for IC circuits using gate arrays, where the design engineer needs only to alter parameters defining the horizontal geometry of devices. An efficient technique has been used to transpose a pre-ordered sparsely-stored circuit matrix, leaving the program's optimal ordering strategy invariant. As a consequence, only one solution of adjoint-type equations is needed at a DC point, or at a frequency (AC) or time point, to compute the sensitivities of an output variable with respect to any number of parameters. In noise computation, one AC solution is sufficient to compute the RMS noise at an output regardless of the number of noise expressions. Furthermore, unlike other programs, the Interactive Circuit Design Program used allows noise expressions that could be functions of an arbitrary set of parameters, voltages, currents, and frequency and therefore, the most commonly used noise sources are covered. Examples show that lab measurement of noise agrees with simulation.