Dual droplet size printhead

Abstract

An ink jet print head has first nozzles of a first diameter for ejecting droplets of ink having a first mass, and second nozzles of a second diameter for ejecting droplets of ink having a second mass. The first diameter is larger than the second diameter, and the first mass is larger than the second mass. First and second heater-switch pairs are connected in parallel on a substrate of the print head. The first heater-switch pairs include first heaters adjacent corresponding first nozzles, and the second heater-switch pairs include second heaters adjacent corresponding second nozzles. The first and second heaters are composed of electrically resistive material occupying first and second heater areas on the substrate. The first heater-switch pairs also include first switching devices connected in series with the first heaters, with each first switching device developing a first switching device voltage drop as a first electrical current flows through. The second heater-switch pairs include second switching devices connected in series with the second heaters, with each second switching device developing a second switching device voltage drop as a second electrical current flows through. The first heater area is larger than the second heater area, thus matching heater area to nozzle diameter to provide for more efficient transfer of thermal energy to the ink. The voltage drop across each first switching device is substantially equivalent to the voltage drop across each second switching device, thus reducing undesirable nozzle-to-nozzle variations in the amount of energy delivered to the ink.