Abstract: Electromigration within heater resistors of printheads is prevented by taking into account a resistance degradation characteristic of the heater resistors. In one method a burn in operation of the printhead heater resistors is provided in order to bring the heater resistor resistance to a substantially stable resistance value. Alternatively, a method of controlling firing of a heater resistor within a printhead of an ink jet printer involves establishing a desired current density or maximum acceptable current density for the heater resistor. A resistance of the heater resistor is thereafter monitored during printing operations. Based at least in part upon the monitored resistance, a firing voltage across the heater resistor is adjusted in order to maintain the desired current density through the heater resistor or in order to hold current density through the heater resistor at or below the maximum acceptable current density.

Abstract: A method of calibrating a linear driver system including a linear driver circuit, logic means connected to an input line of the linear driver circuit, and information storage means associated with the logic means, involves testing the linear driver circuit once assembled. A predetermined test load and a test electrical energy source are connected to the linear driver circuit. A first input test voltage is applied to the input line of the linear driver circuit and a corresponding first current level through the test load is measured. A second input test voltage is applied to the input line of the linear driver circuit and a corresponding second current level through the test load is measured. The two measured current levels are stored in the information storage means for later retrieval during operation of the linear driver system.