An Area Effective Programmable Front-end Amplifier for Neural Signal Acquisition

Acquisition and analysis of neural signals have greatly changed our understanding of the brain. These neural implants are required to be as small as possible so that they are least invasive to normal body functioning. The neural signal contains frequency components from 0.1-10KHz and amplitude in 10-100µV range, which is very small and can be easily distorted by external noise sources. This demands a very area-efficient and low-noise Front-End Amplifier (FEA). Low voltage supply and low power dissipation is another critical requirement to ensure safe implantation and prolonged battery life. Keeping all these requirements in mind, we propose a programmable area efficient and low-noise FEA design along with both manual and SAR-based Gain Tuning and Offset Cancellation Scheme which is robust to any temperature and process variations. The designed FEA occupies a minimal area of 0.05 mm2 which shows great area efficiency w.r.t. switch-capacitor based and closed-loop frontend amplifiers. Obtained maximum voltage gain from Simulation is 87.6 dB, Input-referred noise density is 20 nV/√Hz, and the power consumption is 43.2µW at 1.8V power supply with a Noise Efficiency(NEF) factor of 1.84. The proposed scheme has offset cancellation capacity up to 30 mV using the 7 bits of transistor bank.