An amplifier device including a gain stage, an output stage, at least one phase compensation circuit and at least one coupling suppression device is provided. The gain stage has at least one feedback node. The output stage is coupled to the gain stage and has an output node for outputting an output voltage. Each of the at least one phase compensation circuit is coupled between a corresponding one of the at least one feedback node and the output node. Each of the at least one coupling suppression device is coupled between a corresponding one of the at least one feedback node and a respective coupling node, and is spontaneously turned on in response to a change of a voltage level at the corresponding feedback node when the corresponding feedback node is coupled by noise, thereby suppressing the change of the voltage level at the corresponding feedback node.