Disclosed herewith is a circuit system for improving a slew rate while reducing the power consumption in an operational amplifier that requires a comparatively high supply voltage (e.g., 5 V or upper) operation. The operational amplifier includes level shift circuits, differential pairs whose source connected serially, current voltage conversion circuit and output stage. The level shift circuits convert a differential input signal level and output to differential pairs. Combination of level shift circuit and differential pairs realize input signal difference detection and driving current control in the common circuit.