Operational amplifier circuit capable of improving linearity relation between loading current and input voltage difference

An operational amplifier circuit, comprising:

• a differential input stage circuit, comprising:
• a first input circuit, comprising:
• a first input transistor, having a first terminal, a second terminal, and a control terminal for receiving a first input signal;
• and
• a second input transistor, having a first terminal, a second terminal, and a control terminal for receiving a second input signal;
• a first voltage maintaining circuit, comprising:
• a first tracking transistor having a first terminal, a second terminal coupled to the first terminal of the first input transistor, and a control terminal coupled to the control terminal of the first input transistor;
• and
• a second tracking transistor having a first terminal, a second terminal coupled to the first terminal of the second input transistor, and a control terminal coupled to the control terminal of the second input transistor;
• and
• a first current source, coupled to the second terminals of the first input transistor and the second input transistor;
• and
• a loading stage circuit, for generating a first stage output, wherein the first terminal of the first tracking transistor and the first terminal of the second tracking transistor are respectively coupled to the loading stage circuit, wherein a first loading current flows between the loading stage circuit and the first input circuit through the first tracking transistor, and a second loading current flows between the loading stage circuit and the second input circuit through the second tracking transistor.