  We present a method for solving BPS equations obtained in the
collective-field approach to matrix models. The method enables us to find BPS
solutions and quantum excitations around these solutions in the one-matrix
model, and in general for the Calogero model. These semiclassical solutions
correspond to giant gravitons described by matrix models obtained in the
framework of AdS/CFT correspondence. The two-field model, associated with two
types of giant gravitons, is investigated. In this duality-based matrix model
we find the finite form of the $n$-soliton solution. The singular limit of this
solution is examined and a realization of open-closed string duality is
proposed.
