  We propose a general theory for the critical $T_c$ and pseudogap $T^*$
temperature dependence on the doping concentration for high-$T_c$ oxides,
taking into account the charge inhomogeneities in the $CuO_2$ planes. The well
measured experimental inhomogeneous charge density in a given compound is
assumed to produce a spatial distribution of local $\rho(r)$. These differences
in the local charge concentration is assumed to yield insulator and metallic
regions, possibly in a stripe morphology. In the metallic region, the
inhomogeneous charge density yields also spatial distributions of
superconducting critical temperatures $T_c(r)$ and zero temperature gap
$\Delta_0(r)$. For a given sample, the measured onset of vanishing gap
temperature is identified as the pseudogap temperature, that is, $T^*$, which
is the maximum of all $T_c(r)$. Below $T^*$, due to the distribution of
$T_c(r)$'s, there are some superconducting regions surrounded by insulator or
metallic medium. The transition to a superconducting state corresponds to the
percolation threshold among the superconducting regions with different
$T_c(r)$'s. To model the charge inhomogeneities we use a double branched
Poisson-Gaussian distribution. To make definite calculations and compare with
the experimental results, we derive phase diagrams for the BSCO, LSCO and YBCO
families, with a mean field theory for superconductivity using an extended
Hubbard Hamiltonian. We show also that this novel approach provides new
insights on several experimental features of high-$T_c$ oxides.
