A different approach to calculate the I-V characteristics of p(+)(Ga,Mn)As/n(+)GaAs spin injectors is presented. The vanishing of the spin-extraction transmission coefficients at the spin-split valence-band edges leads us to predict a dip or plateau in the I-V characteristics of this kind of diodes. We show that this minimum, or the inflection point, shifts with the exchange energy. Within this approach and using Kane-like densities of states with a detached impurity band, and exchange energies reported in the literature, excellent agreement is found with observed low-bias features of I-V characteristics.