PURPOSE: To provide a differential amplifier which can be applied to a high- precision signal processing circuit by increasing the voltage gain for low frequency signal input to reduce the gain error of a negatively fed back output signal.

CONSTITUTION: Two current sources I1 and I2 whose one ends are connected to a power terminal 4, a differential transistor TR pair consisting of two FETs M1 and M2 which have gates connected to signal input terminals 1 and 2 respectively and have sources connected to the other end of the current source I1, a current mirror circuit consisting of an FET M3 whose common connection point of the gate and the drain is connected to the other end of the current source I2 and source is connected to a power terminal 5 and an PET M4 which has the gate connected to the common connection point and has the source connected to the power terminal 5 and has the drain connected to the drain of the FET M2 are provided to constitute the differential amplifier.