The invention discloses an operational amplifier with full input and output, wherein the current of an input tube is controlled by current sources unsymmetrical up and down on the basis of an existing operational amplifier with full input and output, a source end of an NMOS differential pair is connected with the source electrode of a first switch transistor, the output end of a first current mirror and a first current source, and a source end of a PMOS differential pair is connected with the source electrode of a second switch transistor, the output end of a second current mirror and a second current source, the drain of the first switch transistor is connected with the input end of the second current mirror, the drain of the second switch transistor is connected with the input end of the current mirror, and the grid of a complementary differential pair of PMOS and NMOS is connected with input differential signals, wherein the first current source is equal to the second current source, and the first current source and the second current source are of 1:3 current mirrors. The operational amplifier with full input and output can keep the transconductance constant in the common mode input range.