A dynamic bias control circuit includes a current source, a first switch, a differential amplifier, and a third switch. The current source outputs a first current. The first switch is coupled to an output end of the current source for generating the first current. The differential amplifier includes a first input end for receiving a reference voltage and a second input end coupled to the first switch. The third switch is coupled to an output end of the differential amplifier and to the first end of the first switch for adjusting a voltage at the first end of the first switch according to a result outputted from the differential amplifier. A control end of the first switch is coupled to a second switch. The second switch is used for inputting a second current into the second switch, wherein the second current to the first current is a predetermined ratio.