Patent ID: 8253835

Claim:
A solid state image sensing device comprising: an image sensing region in which pixels are two dimensionally arranged into rows and columns on a semiconductor substrate, the pixel comprising a photoelectric conversion circuit configured to convert an optical signal into a signal charge and store the signal charge, a read circuit configured to read out the electric charge stored in the photoelectric conversion circuit to a detecting portion, an amplification circuit configured to amplify and output a voltage corresponding to an amount of electric charge in the detecting portion, and a reset circuit configured to reset the electric charge in the detecting portion; a vertical signal line connected to each pixel column in the image sensing region; a switch addition circuit configured to be directly connected to a plurality of vertical signal lines, and add data read out from a plurality of pixels via the plurality of vertical signal lines; a CDS and ADC unit configured to perform noise reduction and analog to digital conversion based on a voltage from the switch addition circuit, the CDS and ADC unit being separated from the switch addition circuit; and a variable load circuit connected to the vertical signal line, and configured to increase an electric current flowing through the vertical signal line when a plurality of pixel rows are simultaneously selected, wherein the variable load circuit comprises load transistors each having a current path connected between the vertical signal line and a ground point, and a bias circuit configured to apply a first bias voltage and a second bias voltage to a gate of each load transistor, and the bias circuit applies the first bias voltage to the gate of each load transistor in a normal operation, and applies the second bias voltage higher than the first bias voltage to decrease a conduction resistance of the load transistor when a plurality of pixel rows are simultaneously selected, thereby increasing an amount of electric current flowing through the vertical signal line.