Method of operating a thermal bend actuator

1. A method of operating a thermal bend actuator of a printhead nozzle arrangement of a printhead using an open actuator test circuit comprising an open actuator test input, a column enable input and a row enable input; a drive transistor operatively linking said thermal actuator to a power supply; a bleed transistor arranged in parallel with the thermal actuator; a sense transistor operatively linking an output of the drive transistor and inputs of the thermal actuator and bleed transistor to a sensing node, said method comprising the steps of:

actuating the actuator to facilitate printing by enabling the column and row enable inputs to deactivate the bleed transistor and to activate the drive transistor to link the thermal actuator to the power supply; and

testing the actuator's continuity by enabling the open actuator test input to activate the sense transistor, so that the thermal actuator is short-circuited and the sense node is pulled high if the integrity of the thermal actuator is open-circuit.

2. The method of claim 1 , wherein the controller includes suitable logic gates to configure the activation or deactivation of the relevant transistors according to voltage levels applied to the respective inputs.

3. The method of claim 2 , wherein the logic gates are selected from the group consisting of: AND, NAND and NOT gates.

4. The method of claim 1 , wherein the controller is configured to record the thermal actuator in a dead nozzle map if the sense node registers high when the open actuator test input is activated.

5. The method of claim 1 , wherein the controller is configured to perform an open actuator test shortly after the printhead has finished printing.

6. The method of claim 5 , which is configured to perform the open actuator test between the printing of different pages of a document by the printhead.

7. The method of claim 1 , wherein the drive, bleed and sense transistors are selected from the group consisting of p-FET and n-FET devices.