  The Kondo problem, for a quantum dot (QD), subjected to an external bias, is
analyzed in the limit of infinite Coulomb repulsion by using a consistent
equations of motion method based on a slave-boson Hamiltonian. Utilizing a
strict perturbative solution in the leads-dot coupling, T, to T^4 and T^6
orders, we calculate the QD spectral density and conductance, as well as the
decoherent rate that drive the systemm from the strong to the weak coupling
regime. Our results indicate thet the weak coupling regime is reached for
voltages larger than a few units of the Kondo temperature.
