A High Input Impedance Low Noise Integrated Front-End Amplifier for Neural Monitoring

Within neural monitoring systems, the front-end amplifier forms the critical element for signal detection and pre-processing, which determines not only the fidelity of the biosignal, but also impacts power consumption and detector size. In this paper, a novel combined feedback loop-controlled approach is proposed to compensate for input leakage currents generated by low noise amplifiers when in integrated circuit form alongside signal leakage into the input bias network. This loop topology ensures the Front-End Amplifier (FEA) maintains a high input impedance across all manufacturing and operational variations. Measured results from a prototype manufactured on the AMS 0.35
$\mu{\text m}$
CMOS technology is provided. This FEA consumes 3.1
$\mu{\text W}$
in 0.042
${\text{mm}}^{2}$
, achieves input impedance of 42
${\text G}\Omega$
, and 18.2
${\text{nv}}/\sqrt{\text{Hz}}$
input-referred noise.