Abstract: The present invention provides an amplifier including an input stage, an amplifier stage, a power stage and a de-gain stage. The input stage is configured to receive an input signal to generate an amplified signal. The amplifier stage is configured to generate a first driving signal and a second driving signal according to the amplified signal. The power stage comprises a first input terminal and a second input terminal, wherein the power stage is coupled to a supply voltage and a ground voltage, for receiving the first driving signal and the second driving signal from the first input terminal and the second input terminal, respectively, and generating an output signal.

Abstract: An interactive communication system includes a wearable device and a network comprising a server and a plurality of base stations for serving the wearable device. The wearable device includes a sensing module, a wireless communication module and a microcontroller. The sensing module senses a position change of a user wearing the wearable device and generates a corresponding sensing signal. The wireless communication module sends a signal to the base stations. The microcontroller dynamically adjusts one of a frequency and a time interval of the sending of the signal from the wireless communication module to the base stations according to the sensing signal.