Patent ID: 7999616

Claim:
An operational amplifier, comprising: an input stage circuit receiving a positive input voltage and a negative input voltage through a positive differential input terminal and a negative differential input terminal respectively, and amplifying the positive input voltage and the negative input voltage to output a first positive output voltage at a first node and a first negative output voltage at a second node; a feedback circuit generating a reference positive output voltage equal to the first positive output voltage at a third node according to the positive input voltage and the negative input voltage; a fixed stage circuit equally amplifying the first negative output voltage and the reference positive output voltage to generate a second positive output voltage at a fourth node and a second negative output voltage at a fifth node; and an output stage circuit generating an output voltage at an output terminal according to a difference voltage between the second positive output voltage and a second negative voltage, wherein the fixed stage circuit has a symmetrical circuit structure to regulate offset voltages of the second node and the third node with the same level.