A transconductance amplifier that generates an output voltage by amplifying a difference between an input voltage and a reference voltage, includes: a differential amplifier circuit including an input differential pair configured to receive the input voltage and the reference voltage and operate according to a tail current, and an output circuit provided as an active load of the input differential pair to generate the output voltage; and a current control circuit configured to control the tail current, wherein the current control circuit is configured to increase the tail current when a current supply condition is satisfied, and the current supply condition is that the input voltage falls below a first threshold voltage which is equal to or lower than the reference voltage, or that the input voltage exceeds a second threshold voltage which is equal to or higher than the reference voltage.