According to one example embodiment, an image sensor is configured to operate in a plurality of operation modes. The image sensor includes a pixel array including unit pixels configured to generate an analog image signal from incident light, a readout circuit configured to generate a digital image signal by converting the analog image signal, and a control module configured to generate control signals for controlling operations of the pixel array and the readout circuit according to an operation mode of the image sensor. A first power voltage for driving the image sensor when the operation mode of the image sensor is an image recognition mode for recognizing a body of a user of the image sensor, is lower than a second power voltage for driving the image sensor when the operation mode of the image sensor is an image capture mode for capturing images by the user.