Patent ID: 7806496
Filing Date: 2010-10-05
Classification: B41J

Abstract:
1. A printhead substrate including an electrothermal transducer configured to eject liquid and a drive circuit including a switching element configured to drive the electrothermal transducer, the drive circuit comprising: a logic circuit configured to control driving of the electrothermal transducer; and a power supply voltage generation circuit configured to generate, from a first power supply voltage applied to the electrothermal transducer, a second power supply voltage for activating the switching element based on a voltage value of a third power supply voltage for activating the logic circuit, wherein, in a case where the voltage value of the third power supply voltage is greater than or equal to a predetermined voltage value, the second power supply voltage for driving the switching element is generated from the first power supply voltage, wherein, in a case where the voltage value of the third power supply voltage is less than the predetermined voltage value, the switching element is not driven by the second power supply voltage, and wherein the power supply voltage generation circuit includes a pull down circuit configured to pull down a power supply line to ground in a state where an output of the power supply voltage generation circuit is turned off.