Patent ID: 7253593

Claim:
An error amplifier comprising: an operational transconductance amplifier, generating a first current according to the voltage difference between a reference voltage and a feedback voltage; a compensation circuit, comprising a compensation resistor, a compensation capacitor, and a Miller circuit operated in a first mode or a second mode, wherein the first terminal of the compensation resistor is coupled to the output terminal of the operational transconductance amplifier, the first and second terminals of the Miller circuit are respectively coupled to the second terminal of the compensation resistor and the first terminal of the compensation capacitor, the capacitance of the compensation capacitor charged or discharged by a second current is C z , the equivalent capacitance generated by the Miller circuit and the compensation capacitance is (1+k)C z where k is a positive constant value determined by the Miller circuit, the second current in the second mode is (1+mk) times that in the first mode where m is a positive decimal fraction determined by the Miller circuit; and a fast transient controller, switching the Miller circuit to the second mode when the feedback voltage exceeds a high voltage level or is below a low voltage level, otherwise the Miller circuit is set in the first mode.