A differential amplifier. A differential pair constructed by a first transistor and the second transistor receives differential input signals. The gate terminals of a third and fourth transistor are coupled to the source terminals of the fourth transistor and the third transistor respectively, and the third and fourth transistor construct a feedback device. This feedback device provides a positive feedback to the differential pair in the differential mode, thereby increasing AC amplitude of the differential amplifier. Further this feedback device substantially brings the drain currents of the first current path and the second current path into coincidence in the Vcom mode.