A Low-Noise Neural Signal Amplifier Achieving 1.6 NEF and 2.56 PEF for Brain-Machine Interface

This paper presents a low-power and low-noise front-end amplifier (FEA) dedicated to recording and preprocessing biomedical signals for brain-machine interface. The FEA employs a current-reused architecture which adopts an inverter-based differential input stage to achieve considerable $g_{m}/I$ efficiency and low noise. With a carefully designed common-mode feedback circuit, the output common-mode voltage of the fully-differential FEA is stabilized within an acceptable margin of error about 1 mV. All transistors in FEA operate in the sub-threshold region, realizing low power consumption. This current-reused FEA implemented in a CMOS 0.18- $\mu \mathbf{m}$ technology provides a noise efficiency factor (NEF) and power efficiency factor (PEF) of 1.6 and 2.56, respectively, corresponding to an input-referred noise of 2.37 $\mu \boldsymbol{V}_{rms}$. This FEA consumes only 2 $\mu \mathbf{A}$ current from 1 V supply and the active area is $0.2 \ \mathbf{mm} \times 0.2$ mm.