The invention discloses a low-voltage and low-power-consumption operational amplifier which comprises a first part, a second part and a third part, wherein the first part serves as an input end and is provided with a differential amplification stage and a transconductance constant control circuit connected with a differential amplification stage circuit; the second part is provided with a folded cascade amplification stage, the folded cascade amplification stage is connected with the differential amplification stage circuit of the first part, then the first part and the second part form first-stage amplification of the operational amplifier; the third part is provided with an AB biasing circuit and a rail-to-rail output stage which are respectively connected with the circuit of the second part, so that the rail-to-rail output stage forms second-stage amplification of the operational amplifier under the control of the AB biasing circuit; the AB biasing circuit comprises a clamping circuit, so that when the operational amplifier provides or absorbs the current of a peripheral circuit, the grid voltage of the rail-to-rail output stage is controlled to enable the operational amplifier to show the characteristic of low power consumption. When the current of the peripheral circuit is provided or absorbed, the characteristic of low power consumption is shown.