Abstract: An inkjet print head comprises an array of print head heater circuits, each associated with a respective print head nozzle. Each heater circuit comprises a heater arrangement (28) and a drive transistor (16) for driving current through the heater arrangement (28). The drive transistor (16) comprises a top gate polysilicon thin film transistor having a field relief doped region (20) beneath the gate, and the heater arrangement comprises a portion of the polysilicon layer which defines the drive transistor channel. This enables a heating resistor and driving thin film transistors (TFTs) (as well as control logic) to be fabricated on large, rectangular substrates using a poly-Si TFT technology.

Abstract: An inkjet print head comprising an array of print head heater circuits, each associated with a respective print head nozzle. Each heater circuit comprises a heater arrangement (12) and a drive transistor (10) for driving current through the heater arrangement (12) connected in series between power lines (VS, GND). The heater arrangement (12) comprises a plurality of diode elements (16) in series. The diode elements have an inherent resistance, to provide the required heating, but the voltage drops across the diode elements enable the voltage across the transistor when in the off condition to be reduced. This enables a reduction in size of the transistor and/or enables a higher supply voltage to be used.