Amplification of a signal by a small circuit size and reduction of a power are achieved.A current controlling current source unit 53 changes an outputting current based on a transition time setting signal tp. A current controlling current source unit 54 changes a drawing current based on a transition time setting signal tn. An amplitude control unit 55 changes a power source voltage supplied to the current controlling current source unit 53 and changes amplitude of a voltage generated by a current outputted from the current controlling current source unit 53, based on amplitude setting signal ap. An amplitude control unit 56 changes a power source voltage supplied to the current controlling current source unit 54 and changes amplitude of a voltage generated by the current drawn by the current controlling current source unit 54, based on amplitude setting signal an. The buffer unit 57 drives a load in accordance with the current outputted from the current controlling current source unit 53 and the current drawn from the current controlling current source unit 54.