An image sensor includes a first column line and a second column line configured to extend in a first direction, a plurality of pixel groups configured to connect to the first column line or the second column line and to comprise a plurality of pixels in each of the plurality of pixel groups, a bias circuit configured to comprise a first current circuit and a second current circuit configured to output different bias currents in a first operational mode, and a switching circuit configured to connect the first column line to the first current circuit and connect the second column line to the second current circuit during a first time period, and to connect the first column line to the second current circuit and connect the second column line to the first current circuit during a second time period subsequent to the first time period in the first operational mode.