The biionic potential of charged membranes has been studied theoretically. A closed, analytical solution to the Nernst-Planck equations describing the multiionic transport through the charged membrane and the diffusion boundary layers has been obtained. Several limiting expressions, corresponding to negligible diffusion boundary layer effects, low bathing solution concentration, and low fixed charge concentration, have been discussed, and the experimental conditions which ensure their validity have been analyzed. The results from the model have been finally compared to recent experimental data corresponding to membranes with high charge density, and the influence of the boundary layers has been found to be significant.