Survey on various architectures of preamplifiers for electroencephalogram (EEG) signal acquisition

Modern-day biomedical science and technology have progressed with implantable neural recording systems. There is a demand for miniaturised devices that can be emplaced into the brain for an efficient neural recording process. In contrast to the commercial gadgets, the design of implantable devices is critical, as they are placed in vital regions of the brain. The design techniques and its specifications should be properly addressed to increase the efficiency of the device. Low power is a vital parameter for the implantable devices, as it is essential that the power consumed is minimised, otherwise the battery would be rapidly drained out. The replacement of the battery comes at the cost of frequent surgery which is not a viable solution. The Electroencephalograms (EEG) are biosignals having a weak amplitude which are corrupted with electrode–skin interferences and low-frequency noise. Therefore a preamplifier stage is necessary for the analog front end of a biomedical signal acquisition system. However, the amplifier should only magnify the physiological signal with no degradation in signal‐to‐noise ratio which implies it should be capable of rejecting noise and interferences. This paper presents a comprehensive review of several low power pre‐amplifiers used in various physiological signal recording applications, along with their performance evaluation in terms of various key parameters such as gain, signal‐to-noise ratio bandwidth, common-mode rejection ratio (CMRR) and more.