Apparatus for dc offset cancellation

A DC(Direct Current) offset cancellation apparatus is provided to remove effectively DC offset without the deterioration of noise figure, thereby improving the performance of a system having the DC offset cancellation apparatus. A DC(Direct Current) offset cancellation apparatus comprises the followings: a main amplifier(40) including an inversion input stage for receiving a first signal and non-inversion input stage for receiving a second signal; a replica amplifier(41) including the inversion input stage for receiving the first signal and the non-inversion input stage for receiving the second signal; a switch(42) for switching signals inputted to the replica amplifier in response to a control signal; and a storing unit(43), which is connected to the input stage of replica amplifier, for maintaining DC value for a predetermined time period when the switch is opened.