An amplifier device includes an amplifier circuitry, a controller circuitry, and an offset cancellation circuitry. The amplifier circuitry is configured to amplify a first input signal and a second input signal, in order to generate a first output signal and a second output signal. The controller circuitry is configured to generate a first control signal and a second control signal according to the first output signal and the second output signal. The offset cancellation circuitry is configured to provide a negative capacitor to the amplifier circuitry, and to adjust at least one current flowing through a circuit, which provides the negative capacitor, of the offset cancellation circuitry according to the first control signal and the second control signal, in order to cancel an offset of the amplifier circuitry.