Printing element substrate, printhead, and printing apparatus

A printing element substrate comprising:

• a printing unit including a printing element and a transistor configured to drive the printing element;
• a logic circuit unit configured to be supplied with a first power supply voltage, and receive print data;
• a unit configured to be supplied with a second power supply voltage, and output a signal from the logic circuit unit to a control terminal of the transistor;
• a voltage generation unit configured to be supplied with a third power supply voltage, and generate, using the third power supply voltage, the second power supply voltage to be supplied to the unit;
• and
• a controlling unit configured to control supply of the third power supply voltage to the voltage generation unit,
• wherein when the first power supply voltage is not supplied to the logic circuit unit, the controlling unit does not supply the third power supply voltage to the voltage generation unit.