PURPOSE: To provide a photodetector of a touch input device, etc., which actuates many light emitting elements with high efficiency and almost even luminance by means of a power supply of a low voltage level of about 5V that is used for drive of a normal logic circuit.

CONSTITUTION: Many light emitting element groups (matrices) 70 of infrared LEDs, etc., are successively selected by a source driver 60 and a sink driver 80 under the control of a controller 30. Then the selected light emitting elements are driven with high luminance by the large current that is supplied from a common charge pump circuit 50 which operates via a power supply of a low voltage level. Under such conditions, many light emitting elements can be driven with almost constant luminance by the power supply of low voltage regardless of variance of the electrical characteristics of the light emitting elements and a selection drive circuit.