PURPOSE: An image sensor and a portable device including the same are provided to prevent an arm current from inflowing in a floating diffusion area. CONSTITUTION: A transmission transistor (13) transmits a current generated by a photo detector (11). A reset transistor (17) is connected between a node supplying a power voltage and a floating diffusion node. A source follower output transistor (21) converts a charge stored in the floating diffusion node into an output voltage. A first selection transistor (25) is connected between the source follower output transistor and a current source (34). A second selection transistor (29) is connected between the floating diffusion node and a source follower gate (23).
