Patent ID: 7642853

Claim:
An operational amplifier comprising: a first power supply node; a second power supply node, wherein a supply voltage is present between the first power supply node and the second power supply node; an amplifier output node; a differential input stage; an output stage comprising: a first transistor having a source, a gate and a drain; a second transistor having a source, a gate and a drain, wherein the amplifier can couple the amplifier output node to the second power supply node through a first conductive path, wherein the first conductive path extends from the output node, through the second transistor, through the first transistor, and to the second power supply node; a third transistor having a source, a gate and a drain; a fourth transistor having a source, a gate and a drain, wherein the amplifier can couple the amplifier output node to the first power supply node through a second conductive path, wherein the second conductive path extends from the first power supply node, through the third transistor, through the fourth transistor and to the amplifier output node, wherein each of the first, second, third and fourth transistors has a drain-to-source breakdown voltage that is lower than the supply voltage, and wherein each of the first, second, third and fourth transistors has a gate-to-source breakdown voltage that is lower than the supply voltage; and an adaptive biasing circuit that supplies a first bias signal onto the gate of the second transistor and that supplies a second bias signal onto the gate of the fourth transistor, wherein the first bias signal has a first voltage if an output signal on the amplifier output node is in a first voltage range, and wherein the adaptive biasing circuit increases the first bias signal if the amplifier output signal is in a second voltage range, wherein the second bias signal has a third voltage if an output signal on the amplifier output node is in a third voltage range, and wherein the adaptive biasing circuit decreases the second bias signal if the output signal is in the second voltage range.