To obtain an MOS transconductance amplifier which has a satisfactory linear transconductance over its whole operation input voltage range and is suitably realized on a semiconductor integrated circuit.

An MOS differential pair 1 is formed by source-connected MOS transistors M1 and M2. An input voltage Vi is applied across the gates of M1 and M2. As the loads of M1 and M2, MOS transistors M3 and M4 with a bias voltage VB applied in common to their gates are respectively connected. Drain currents ID1 and ID2 with a square characteristic are linearized by M3 and M4 and taken out from the drains of M1 and M2 as a differential output voltage ΔV0.