An Energy-Efficient Impedance-Boosted Discrete-Time Amplifier Achieving 0.34 Noise Efficiency Factor and 389 MΩ Input Impedance

This paper presents a noise-efficient analog front end (AFE) for low-power sensor systems. The proposed AFE employs a low-noise amplifier based on series-parallel converters whose input impedance is boosted to 389 $\mathrm{M}\Omega$ ($39 \times$ improvement compared to prior work) using an input-resistance boosting loop and a capacitive positive feedback loop. The AFE achieves the lowest reported noise efficiency factor (NEF) and power efficiency factor (PEF) of 0.34 and 0.1, respectively, while consuming 370 nW.