  In the weak coupling limit, we investigate two-leg ladders with a unit cell
containing both Cu and O atoms, as a function of doping. For purely repulsive
interactions, using bosonization, we find significant differences with the
single orbital case: a completely massless quantum critical regime is obtained
for a finite range of carrier concentration. In a broad region of the phase
diagram the ground state consists of a pattern of orbital currents plus a
density wave. NMR properties of the Cu and O nuclei are presented for the
various phases.
