A slew rate adjusting circuit includes an adjustment transistor configured to provide an adjustment current into an output port of an arithmetic amplifier, a first transistor connected between a power line of the arithmetic amplifier and the adjustment transistor, and a second transistor connected between the first transistor and an output node of the output port, wherein the adjustment transistor is turned on by the second transistor in response to a difference between an input voltage and an output voltage being equal to or greater than a reference voltage, and the adjustment current is provided to the output port in response to the adjustment transistor being turned on.