Image sensor for reducing channel variation and image processing system including the same

An image sensor for reducing channel variation and an image processing system including the same. The image sensor includes first to mth pixels (m≧2), each of which is connected to a corresponding column line from among first to mth column lines and is configured to output a respective pixel signal.' The image sensor further includes first to mth bias circuits, each of which is connected to a corresponding column line from among the first to mth column lines and is configured to fix a voltage of the corresponding column line to a bias voltage when a column line-specific pixel is not selected to output the respective pixel signal. An analog-to-digital converter in the image sensor is configured to convert the pixel signals into digital signals.