Design of a High-Performance Amplifier for Brain Computer Interface

In the recent past, there has been growth centred around the field of sensing particularly in biomedical applications. Biomedical signals can be broadly categorised into two parts, 1) Endogenous signals that can be observed from natural physiological processes and measured within or on living creatures. Endogenous signals include ECG, EEG, blood glucose etc. 2) Exogenous signals usually applied non-invasively to measure internal structures and parameters. Major challenges with biomedical signal-acquisition originate from limited or no user-access to signal- sources, noise, low frequency of operation and small amplitude. For example, EEG signal lies in the microvolt region (2-100μV) and in the frequency spectrum up to 100Hz. Therefore, such signals need to be amplified before they can be subjected to signal processing for analysis and feature extraction. In this work, we propose design of the preamplifier stage in Brain Computer Interface which forms the component between the EEG signal acquisition and signal processing. We have designed a high gain, high performance operational transconductance amplifier (OTA) using 𝑔mId methodology in CMOS 180nm process GPDK technology library with a supply voltage of 1.8V. This design has a gain of 62.3dB and a low pass filter was designed using the developed circuit in closed loop configuration with a 3dB bandwidth of 100Hz