Image sensor including dark current removal

An image sensor comprising:

• a pixel array comprising active pixels receiving light and optical black (OB) pixels shielded from light;
• a plurality of comparators respectively provided for each column of the pixel array and configured to compare pixel signals of the pixel array that are input through a first input terminal with a ramp signal that is input through a second input terminal to output comparison signals;
• a plurality of counters respectively provided for each column of the pixel array and configured to output count values based on the comparison signals;
• an image signal processor (ISP) configured to generate dark current data using the count values based on pixel signals of the OB pixels;
• a digital-to-analog converter (DAC) configured to generate an OB voltage corresponding to the dark current data;
• and
• a dark current removal circuit provided for each column of the pixel array and configured to reflect the OB voltage in at least one of the pixel signals of the active pixels input to the plurality of comparators and the ramp signal,
• wherein the dark current removal circuit comprises
• a plurality of switches,
• a first capacitor having a first end at which a pixel signal from among the pixel signals of the pixel array is applied, and a second end connected to the first input terminal,
• a second capacitor having a third end at which the ramp signal is applied, and a fourth end connected to the second input terminal,
• a third capacitor configured to apply a compensation voltage to the first input terminal based on operation of the plurality of switches, and
• a fourth capacitor configured to apply the compensation voltage to the second input terminal based on operation of the plurality of switches.

A method of operating an image sensor comprising active pixels receiving light and optical black (OB) pixels shielded from light, the method comprising:

• obtaining dark current data by reading out pixel signals of the OB pixels;
• generating an analog voltage corresponding to the dark current data;
• and
• removing a noise component, caused by dark current, from pixel signals of the active pixels using the analog voltage,
• wherein the image sensor comprises a comparator having a first input terminal at which a pixel signal from among the pixel signals of the active pixels is applied, and a second input terminal at which a ramp signal is applied, and
• the removing of the noise component comprises reflecting, by a dark current removal circuit, the analog voltage in at least one of the first input terminal and the second input terminal during a readout period of an active pixel,
• wherein the dark current removal circuit comprises
• a plurality of switches,
• a first capacitor having a first end at which the pixel signal is applied, and a second end connected to the first input terminal,
• a second capacitor having a third end at which the ramp signal is applied, and a fourth end connected to the second input terminal,
• a third capacitor configured to apply a compensation voltage to the first input terminal based on operation of the plurality of switches, and
• a fourth capacitor configured to apply the compensation voltage to the second input terminal based on operation of the plurality of switches.