Dc offset cancellation circuit and programmable gain amplifier using it

A DC(direct Current) offset cancellation circuit and a programmable gain amplifier using the same are provided to reduce generally the number of devices by reducing an operational amplifier used in the programmable gain amplifier. A DC offset cancellation circuit includes an operational amplifier(301), a first resistance(302), a second resistance(303), a DC offset cancellation resistance(304), and a capacitor(305). The operational amplifier(301) has an inverting input terminal, a non-inverting input terminal, and an output terminal. One end of the first resistance(302) is connected to the inverting input terminal and an input signal is applied to the other end of the first resistance. Both ends of the second resistance are connected to the inverting input terminal and the output terminal separately. Both ends of the DC offset cancellation resistance are connected to the inverting input terminal and the non-inverting input terminal separately.