An Analog Front-End With Reconfigurable Biasing for Broadband Noise Optimization of Biosensing

Abstract

In the design of ultra-low-noise biosensing analog front-ends, input stage noise optimization remains a critical challenge. This paper presents a reconfigurable capacitive transimpedance amplifier designed for broadband biosensing applications with optimized noise performance. The proposed architecture employs a digitally controlled biasing scheme that adaptively configures the geometry and bias current of the input stage according to the sensor capacitance and target bandwidth. Post-layout simulations in a 40 nm CMOS process demonstrate a consistent transimpedance gain of $154.5 \mathrm{~dB} \Omega$ across all configurations, with bandwidth scalable from 3 MHz to 82.3 MHz. Input-referred noise is minimized over a sensor capacitance range of 0.4 pF to 6 pF. For a sensor capacitance of 4 pF, the simulation result shows 29.7 pA and 7.3 nA input-referred RMS noise at 500 kHz and 80 MHz bandwidth, respectively. The proposed front-end achieves improved noise efficiency with increasing bandwidth, making it suitable for measurements of ion channels, nanopores, and other biosensing applications.