Ohmic heating matrix

Several embodiments of an apparatus for directly driving all addressed and unaddressed resistive heating elements in a matrix of heating elements is disclosed. Since the unaddressed heating elements are directly driven, the parasitic voltages that are found across unaddressed heating elements in prior-art arrays are replaced with specified constant voltages. Additionally, the variation in total power dissipation of all the heating elements in the matrix can be reduced. When a matrix of directly driven heating elements is used in a thermal printer or thermal-ink-jet printer several advantages are realized. The directly driven unaddressed heating elements have a specified low voltage across them instead of a parasitic voltage which may have a magnitude large enough to cause the printhead to misfire. Additionally, the reduction in the variation of the total power dissipation reduces the variation in the printhead temperature which reduces the variation in the printed dot size.