A Front-End Amplifier With Current Compensation Feedback Input Impedance Booster for Neural Signal Applications

In integrated circuit form, the front-end amplifier (FEA) determines the fidelity of the biosignal detection, signal-to-noise ratio, power consumption and detector size for the future multi-channel neural signal recording systems and applications. Especially for the high-density implantable applications, a higher input impedance reduces the signal attenuation (with respect to the high-impedance miniature electrodes), and lowers the current into the tissue (to avoid the overheating damage). In this paper, an input impedance booster with current compensation feedback technique is proposed, it neutralizes any currents generated at input of FEA without affecting the gain. It substantially yields a high input impedance across process and device mismatches. The proposed front-end circuit is implemented on a 0.18μm CMOS process, it achieves an input impedance of approximately 60 GΩ, and CMRR of 61 dB with 57 dB PSRR. The input-referred noise is approximately 5.6 μv/√Hz while consuming 7.6 μW in 0. 025mm
²
chip area.