Printhead, head cartridge, and printing apparatus employing either of same

A printhead that minimizes increased size and cost of an apparatus by reducing a number of input pads, while making use of the advantages of employing a differential input circuit. This printhead has an input pad to which a differential signal obtained by superimposing two or more logic signals is input. The differential input circuit includes a circuit that disassembles the differential signal input via the input pad into separate logic signals.