LIGHT QUANTITY DETECTING CIRCUIT, ELECTROOPTICAL DEVICE, AND ELECTRONIC EQUIPMENT

摘要

PROBLEM TO BE SOLVED: To eliminate the need for a high-impedance input circuit or not make a transistor for light quantity detection large in size. SOLUTION: A light quantity detecting circuit includes a TFT 11 which is applied with a predetermined voltage at its gate electrode to generate a current corresponding to the quantity of photodetection and flowing to source and drain electrodes; a capacitance element 14 connected between a high-potential power supply line and a low-potential power supply line in series with the TFT 11, a TFT 12 having source and drain electrodes connected to the capacitance element 14 in parallel; a pulse generating circuit 15 which switches the source and drain of the TFT 12 from a mutual conduction state to a non-conduction state; and a TFT 13 which is provided in a light-shielded region and has its gate electrode connected to the gate electrode of the TFT 11 to generate a constant current Iref flowing to source and drain electrodes. COPYRIGHT: (C)2008,JPO&INPIT