A differential amplifier has an interpolating function and has: first and second differential pairs including transistors of a first conductivity type; third and fourth differential pairs including transistors of a second conductivity type; first and second current sources providing operating currents to the first and second differential pairs; third and fourth current sources providing operating currents to the third and fourth differential pairs; a first control circuit which controls, in a first operating range where the amounts of currents flowing through the first and second differential pairs become smaller, respectively, a changing point at which the operating current of the first differential pair changes; and a second control circuit which controls, in a second operating range where the amounts of currents flowing through the third and fourth differential pairs become smaller, respectively, a changing point at which the operating current of the fourth differential pair changes.