The present invention is gallium nitride based operational amplifier because reliability and performance of the gallium nitride is better than the silicon counterpart in radiation environment. The operational amplifier includes four stages, first stage is dual input balanced output differential amplifier, second stage is dual input unbalanced differential amplifier, third stage is buffer stage to couple second and fourth stage, and fourth stage is cascaded common source amplifier with degeneration. A capacitor coupled between second and third stage is to enhance the stability of operational amplifier.