Patent ID: 7265593

Claim:
A circuit for enhancing a slew rate of an operational amplifier by providing an assistant current to a main output stage outputting a main current, comprising: a monitoring stage for receiving signals from the main output stage and outputting a push signal and a pull signal, wherein the main output stage comprises a first field effect transistor with a first type and a second field effect transistor with a second type, the gates of the first and second field effect transistors are connected to an output of a differential amplifier and the main current further comprises a quiescent DC biased current, and the push signal and the pull signal are level shifted from the output of the differential amplifier; an assistant output stage comprising a third field effect transistor with the first type and a fourth field effect transistor with the second type, wherein a first input and a second input of the monitoring stage are connected to the gate of the first field effect transistor with the first type and the gate of the second field effect transistor with the second type, respectively, so as to receive signals from the main output stage, and then a first output and a second output of the monitoring stage are connected to the gate of the third field effect transistor with the first type and the gate of the fourth field effect transistor with the second type, respectively, so as to output the push signal and the pull signal to the assistant output stage; and a gamma curve generating device, wherein the gamma curve generating device receives the main current to output at least one gamma reference voltage for adjusting a gamma curve.