The main purpose of this work is to show how with a simple analytical model of diffusion, using only R and xj experimental data, is it possible to calculate the relationship between the electrically active charge and the initial implanted dose of Antimony in Silicon. It will be shown that Qel/Qdose ≪ l in agreement with many others authors1,2,3, and a lower diffusion coefficient than that commonly used by SUPREM II simulator is achieved through this model, which allows good fit with the experimental data.