A smooth model of a system with diode nonlinearity following the ordinary differential equation with a large parameter $K$ is proposed. It offers a convenient tool for numerical analysis using the advanced packages of the applied programs. The main result of this paper is presented in a theorem that gives the upper bound of the modeling error and shows that the model solution uniformly converges to the exact solution of system with diode nonlinearity when $K$ tends to infinity. The usefulness of this model is illustrated via a concrete example.