This paper presents an equivalent electrical circuit for one dimensional substrate minority carriers spice simulation. The electrical circuit parameters are extracted from substrate meshing applying the finite difference method. This model is derived from a linearization of drift-diffusion equations and not from the closed form solution. Further, the proposed circuit is solved with available SPICE simulators because of electrical analogies with physical quantities. Spice simulation results are compared with device simulator results. The accuracy of the model is dependent on the number of the discretization elements used. The minority carrier diffusion current is included automatically in the total substrate current computation.