A differential amplifier having a tunable filter is disclosed. The tunable filter may attenuate some common-mode signals while not affecting amplification of differential signals. The tunable filter may include a resonant circuit to select frequencies of common-mode signals to attenuate. The resonant circuit may include a variable capacitor series-coupled to an inductor. A resonant frequency of the resonant circuit may be determined, in part, by a capacitance value of the variable capacitor.