US Patent 7663439 Operational amplifier

The operational amplifier adapting to a source driver is provided herein. The operational amplifier includes the input module, the first and the second current mirror module, the switch control module and output stage module, wherein the input module includes the first and the second differential pairs. The first current mirror module provides the first bias current to the first differential pairs and outputs the first mirrored current. The second current mirror module receives the second bias currents and the second mirrored current from the second differential pairs. The first and the second mirrored currents are respectively generated by mirroring the first and the second bias currents. The switch control module adjusts the first and the second bias currents for controlling the operation of the output stage module. The output stage module generates an output voltage terminal to a panel load according to the first and the second mirrored currents.