# A Novel Battery-Supplied AFE EEG Circuit Capable of Muscle Movement Artifact Suppression
## 1 Introduction
### Design Specifications in Medical-Grade and Research-Grade EEG Generic Circuit Design  
In EEG generic circuit design, various subcomponents work together for accurate brain wave signal capturing and denoising. One of the most characteristic examples of these is the filter subcomponents such as notch, anti-aliasing, high-pass, and low-pass filters, which refine signals by eliminating interference and keeping only the frequency bands of interest from the input raw EEG signal [22]. Another example is the circuit subcomponents, including chopper circuits and electrostatic discharge protection (ESD), which minimize low-frequency noise and protect against electrostatic discharge damage. Additionally, the amplifier subcomponents, such as Operational Amplifiers, Programmable Gain Amplifiers, and Instrumentation Amplifiers, amplify signals with high fidelity [23]. Furthermore, the Analog Multiplexers select signals in multi-channel setups, while the Analog to Digital Converter digitizes the collected signals from the electrodes for further analysis [24]. Moreover, the driven-right-leg circuit reduces interference by introducing a feedback loop between the EEG device and the human body [22]. Last but not least, the power supply subcomponents, such as batteries and regulators, ensure a stable power supply for the device. These integrated subcomponents create a prototypical EEG generic circuit design for detailed brain activity analysis. The particular order of the subcomponents and the choice of incorporating some of them in the design, along with their multiplicity, are some of the engineering problems of constructing a functional and appropriate EEG device. As is apparent, each engineering decision has trade-offs that must be well understood for the design to meet its predefined requirements.  
In the design of circuits for medical-grade and research-grade EEG applications, several essential specifications are critical, and specific requirements should be met. These circuits may have a bandwidth ranging from 0.01 Hz to 20 kHz (maximum frequency application--identifying Directional Hearing Cues), covering a broad spectrum of brain activity pertinent to diverse research and medical requirements [25; 26]. In addition to the aforementioned point, managing noise levels is crucial, particularly during the initial stages before the first amplification. It is essential to keep the 0.1 to 10 Hz noise below 1 \(\upmu\)Vpp [27], and ideally under 0.4 \(\upmu\)Vpp, to ensure clear signal quality and a high signal-to-noise ratio (SNR) [28]. Furthermore, it must be stated that the EEG signal of interest always appears as an AC differential voltage signal in the raw input EEG data. Consequently, a high Common Mode Rejection Ratio (CMRR) exceeding 90 dB is deemed crucial for filtering out the common components of the input signals that are the major carriers of the noise artifacts and undesirable DC offsets [29]. It is also important to note that compliance with regulations requires ensuring that no more than 10 \(\upmu\)A of current returns to the body, along with mandatory ESD protection [30; 31; 32]. The sub-circuits analyzed above are instrumental in achieving signal integrity, thereby ensuring the accuracy and reliability of the data collected. Each design must be tailored to its intended use and optimized for the particular sub-audience that it appeals to in the field of Neuroscience and Medical practice.