A Low-Distortion Current-Mode Signal Generator for Wide-Range Bioimpedance Spectroscopy

Abstract

This paper presents a low-distortion current-mode sinusoidal signal generator for bioimpedance spectroscopy measurements. The proposed full current-mode operation enables linearity enhancement and potential savings in silicon area and power consumption. Programmability in the low-pass filter and current driver enables impedance measurements from $0.2\ \Omega$ to $10\ \mathrm{k}\Omega$ over a wide frequency range from 1 kHz to 1 MHz. The current generator, designed in a $0.18\ \mu \mathrm{m}$ CMOS process, consumes between $736\ \mu \mathrm{W}$ at the lowest frequency and gain, and 1.70 mW at the highest frequency and gain, and occupies 1.76 mm2 silicon area. Post-layout simulation results show a spurious-free dynamic range larger than 40 dBc over the entire frequency range, which enables bioimpedance measurements with errors below 1%, as it is required for wearable devices evaluating neuromuscular disorders.