EI-NK: A Robust Exponential Integrator Method With Singularity Removal and Newton–Raphson Iterations for Transient Nonlinear Circuit Simulation

In this article, we propose an exponential-integrator-Newton–Krylov (EI-NK) method for transient simulation of large-scale nonlinear circuits. This method aims to address two long-standing problems that affect the performance and robustness of EI in handling nonlinear circuits. First is the numerical instability caused by the singularity in the differential-algebraic equation system. We provide an in-depth analysis of the problem and propose a systematic, algebraic, and sparsity preserving regularization technique to eliminate the unstable modes in the system to be solved. Next, we develop a scheme to enable the iterative Newton–Raphson solution in the EI framework for enhanced nonlinearity handling capability. With the two techniques, we wish to elevate EI’s robustness and performance and make it a competitive alternative to the existing SPICE-type simulators in practical applications.