Design of a Compact Amplifier and Signal Conditioning Module for Wireless EEG Monitoring

Electroencephalogram (EEG) is an electrical recording of brain activity. It has numerous diagnostic and research applications in the study of the brain. EEG can be recorded from the human brain by the placement of electrodes on the surface of the scalp, but the signals thus picked up are very small (on the order of a few microvolts) to be recorded or digitized (for example by an A/D converter). Hence an amplification system is required to amplify these small potentials to an acceptable level. Further, due to the small amplitude, these signals are very susceptible to any background noise which could be picked up by the human body through the ground path or the cables connecting the recording unit to the electrode. So, a signal conditioning circuit is required which is capable of filtering certain high and low frequency components of the input signal while allowing only the signal in the desired bandwidth to pass. The complete block diagram for the circuit is shown in Figure 1. This paper discusses the design of a compact amplifier suitable for this purpose and the considerations in the design of the amplifier. One of the main concerns in the design of this new amplifier was the need to make it compact and thus useful in portable and wearable patient monitoring equipment. It also needs to be a low-power system in order to be able to power it using batteries. The design presented here uses commercially available surface-mount components to ensure a low-cost design with a relatively smaller footprint. The characteristics of the developed amplifier such signal-to-noise ratio, frequency response and gain are presented in this paper. Some of the measured EEG data is also presented.