US Patent 7604312 Fluid ejection device with feedback circuit

A fluid ejection assembly includes drop ejecting elements arranged in zones, with each zone having at least one drop ejecting element, wherein the drop ejecting elements of each zone are configured to conduct electrical current between a corresponding supply voltage and a corresponding reference voltage. Up to all drop ejecting elements of a group of the drop ejecting elements are enabled to conduct at a given time, with each conducting drop ejecting element of the enabled group having a corresponding drop ejecting voltage. A zone controller is configured to provide a corresponding desired supply voltage for each zone based on at least one corresponding zone parameter of each zone. An energy controller is configured to couple across each conducting drop ejecting element of the enabled group and regulate the supply voltage for each zone based on selected corresponding drop ejecting voltages and on each zone's corresponding desired supply voltage.