A dual point user input is recognized on a touch based user input device that is only capable of outputting a single input position signal by forming or detecting a first position signal, preferably storing the position signal, forming or detecting a subsequent second position signal and determining if the second position has its source in a simultaneous dual point user input. The disclosed amplifier adopts an architecture in which a common-source circuit stacks against a common-gate circuit. The device for being lubricated is located in the accommodating chamber. A gate driver supplies scan pulses to the respective gate lines.