Patent ID: 6914485

Claim:
An input stage for an operational amplifier that is arranged to operate with a high supply voltage, comprising: a first source follower circuit that is configured to receive a non-inverting input signal at a first input, and arranged to provide a first input signal in response to the non-inverting input signal; a second source follower circuit that is configured to receive an inverting input signal at a second input, and arranged to provide a second input signal in response to the inverting input signal; a differential transistor pair that includes a first and second transistor, wherein the first transistor is arranged to provide a first current in response to the first input signal, and wherein the second transistor is arranged to provide a second current in response to the second input signal, wherein the first and second currents flow into a first node that is common between the first transistor and the second transistor; a third transistor that is coupled between the first source follower circuit and a power supply node, wherein the third transistor includes a control terminal that is coupled to a second node; a fourth transistor that is coupled between the second source follower circuit and the power supply node, wherein the fourth transistor includes a control terminal that is coupled to the second node; a current source that is coupled between the second node and the power supply node; and a first voltage source that is coupled between the first node and the second node.