Imaging apparatus includes a printhead with one or more nozzles, wherein heaters are positioned proximate to the nozzles. A surface of at least one kind of the inorganic oxide powders is covered with a coating material selected from the group of 1) a fatty acid metal salt, 2) a wax having a melting point of 40\xb0 C. A parameter control unit judges whether an adjusted weight is located closer to an optimal value than a reference value, and according to the judgment result, changes a step size which is used in the predetermined calculations performed by a reception weight calculating unit, to determine the extent to which the weight should be adjusted. A current mirror type load circuit is provided as a load circuit of the reference memory cell and the main memory cell. A rear feed gate assembly for selectively covering the opening of the tailgate is provided.