Patent ID: 7850262

Claim:
A head substrate comprising: a plurality of printing elements; a plurality of driving elements which are provided in correspondence with said plurality of printing elements and drive said plurality of printing elements; a reference voltage generation circuit which generates a reference voltage; a reference current generation circuit which generates a first reference current on the basis of the reference voltage generated by said reference voltage generation circuit; a plurality of constant current sources, each of which generates a constant current to drive said plurality of printing elements on the basis of the first reference current generated by said reference current generation circuit; an input circuit which inputs an image signal related to driving of said plurality of driving elements; a switch which controls supply of the first reference current; and a detection circuit which detects presence/absence of driving of said plurality of driving elements, based on a result of AND operation of the image signal inputted by said input circuit and a timing signal used for determining an ON/OFF control timing of said switch, wherein said switch is ON/OFF-controlled in accordance with a detection result by said detection circuit.