Operational amplifier using single-stage amplifier with slew-rate enhancement and associated method

An operational amplifier comprising:

• a single-stage amplifier, arranged to receive an input signal and amplify the input signal to generate an output signal, wherein the single-stage amplifier comprises a voltage controlled current source circuit that operates in response to a bias voltage input;
• and
• a current controller, coupled to the voltage controlled current source circuit, wherein the current controller is arranged to receive the input signal, and generate the bias voltage input according to the input signal;
• wherein the bias voltage input comprises a first bias voltage, a second bias voltage, a third bias voltage, and a fourth bias voltage;
• and none of the first bias voltage, the second bias voltage, the third bias voltage, and the fourth bias voltage is directly set by the input signal of the single-stage amplifier.