Abstract
This paper presents a low-noise, front-end sensor IC that includes both AC impedance spectroscopy and DC amperometric measurement capabilities for electrochemical and biosensor applications. A common-gate current buffer topology is proposed that supports both current-mode and voltage-mode sensor signals to allow an input frequency range from DC to 100 kHz. Low-noise operation is achieved across a wide input frequency range using tunable high-pass and low-pass frequency response. In addition, an incremental delta-sigma modulator with embedded frequency response analysis serves as both on-chip impedance analyzer and current-driven analog-to-digital converter. Implemented using a 0.18 μm CMOS process, this work achieves 45 fA/√Hz input current noise density at 1 kHz. Input dynamic range exceeding 80 dB is achieved up to 10 kHz bandwidth, with a maximum of 104 dB dynamic range at 10 Hz.