An ambient light sensor circuit, comprising: a transistor electrically coupled to a first power source; a first capacitive element electrically coupled between a control electrode of the transistor and a first reference power source (V REF1); a second capacitive element electrically coupled between the first capacitive element and a second reference power source (V REF2); a first light receiving element electrically coupled between the first (V REF1) and a third reference power source (V REF3) and controlling a coupling voltage of the first capacitive element and charge/discharge voltages of the second capacitive element by conducting current in response to ambient light, the coupling voltage of the first capacitive element being the voltage applied to the control electrode of the transistor; a first switch electrically coupled to the transistor and enabling the transistor to output current from the first power source according to the coupling voltage of the first capacitive element; a second switch electrically coupled between the first light receiving element and the first capacitive element and interrupting a leakage current of the first light receiving element, thereby preventing the coupling voltage of the first capacitive element from being changed; characterised by: a third switch electrically coupled between the first reference power source (V REF1) and the second switch so as to apply a first reference voltage from the first reference power source (V REF1) to the first and second capacitive elements via the second switch; a fourth switch electrically coupled between a control electrode of the transistor and the first switch and enabling the transistor to form a diode-connected structure; a fifth switch electrically coupled between the first switch and a reference current source (I REF) so as to apply a reference current to the transistor via the first switch, thereby applying a predetermined voltage to the control electrode of the transistor; and a sixth switch electrically coupled to the first switch and enabling the transistor to transmit a predetermined current to an output terminal (I OUT) via the first switch from the first power source in response to the coupling voltage of the first and second capacitive elements. a transistor electrically coupled to a first power source; a first capacitive element electrically coupled between a control electrode of the transistor and a first reference power source (V REF1); a second capacitive element electrically coupled between the first capacitive element and a second reference power source (V REF2); a first light receiving element electrically coupled between the first (V REF1) and a third reference power source (V REF3) and controlling a coupling voltage of the first capacitive element and charge/discharge voltages of the second capacitive element by conducting current in response to ambient light, the coupling voltage of the first capacitive element being the voltage applied to the control electrode of the transistor; a first switch electrically coupled to the transistor and enabling the transistor to output current from the first power source according to the coupling voltage of the first capacitive element; a second switch electrically coupled between the first light receiving element and the first capacitive element and interrupting a leakage current of the first light receiving element, thereby preventing the coupling voltage of the first capacitive element from being changed; a third switch electrically coupled between the first reference power source (V REF1) and the second switch so as to apply a first reference voltage from the first reference power source (V REF1) to the first and second capacitive elements via the second switch; a fourth switch electrically coupled between a control electrode of the transistor and the first switch and enabling the transistor to form a diode-connected structure; a fifth switch electrically coupled between the first switch and a reference current source (I REF) so as to apply a reference current to the transistor via the first switch, thereby applying a predetermined voltage to the control electrode of the transistor; and a sixth switch electrically coupled to the first switch and enabling the transistor to transmit a predetermined current to an output terminal (I OUT) via the first switch from the first power source in response to the coupling voltage of the first and second capacitive elements.