Patent ID: 7443233

Claim:
A DC offset canceling apparatus comprising: a main amplifier receiving an input signal at a main amplifier inverting input having a first sign and a main amplifier non-inverting input having a second sign; a replica amplifier comprising a structure that is substantially the same as a structure of the main amplifier, the replica amplifier receiving the input signal at a replica amplifier inverting input having the first sign and a replica amplifier non-inverted input having the second sign, and having an output connected to an output of the main amplifier, an output of the replica amplifier having a replica amplifier output sign that is the opposite of a main amplifier output sign of the output of the main amplifier; a switch switching the signal input to the replica amplifier in response to a control signal; and a storage unit connected to an input terminal of the replica amplifier to maintain a DC value for a predetermined period of time when the switch is open.