In the analog front-end stage, the amplifier and bandwidth limiter circuits are included to
make more robust and reliable EEG signals from the sensitive raw signals. Because the amplitude
of EEG signals is quiet small, the pre-amplification of the measured EEG signals at
the analog front end is extremely important. In this amplification process, many developed
wireless BCI systems use operational amplifiers or instrumentation amplifiers. Those amplifiers
normally provide a gain ranging from thousands to hundreds of thousands. Amplifica