Wide-Band Compact 1.8 V-0.18 μm CMOS Analog Front-End for Impedance Spectroscopy

Abstract

In this letter, a fully integrated configurable 1 front-end for Impedance Spectroscopy (IS) is presented. The 2 circuit includes fully differential in-phase and quadrature chan-3 nels, using a transconductor (TC)-transimpedance (TI) approach. 4 The input TC, shared for both channels, is based on a pro-5 grammable degenerated differential pair to attain low-noise 6 programmable-gain, while identical TI I/Q with embedded syn-7 chronous rectification provide both I,Q outputs, filtered through 8 f c adjustable G m -C integrators. It exhibits a programmable gain 9 ranging from 0 dB to 40 dB with 87 MHz bandwidth, ampli-10 tude and phase recovery errors below 1.9% and 2.5 • respectively 11 and an input referred noise floor of 16.7 nV/ √ Hz. The result is 12 a high-performance very compact topology with a total power 13 consumption of 292 µW at a 1.8 V power supply, thus consti-14 tuting an appropriate solution for full on chip multichannel IS 15 systems. 16 Index Terms-Low-voltage low-power (LVLP), CMOS ana-17 log front-end, impedance spectroscopy (IS), synchronous 18 demodulator, system on chip (SoC). 19 I. INTRODUCTION 20 M ANY emerging sensors, especially those based 21 on bio and nano-materials, rely on Impedance 22 Spectroscopy (IS), i.e., the sensor information is obtained from 23 its impedance extraction over a specific frequency interval. 24 However, despite its promising applications -from environ-25 mental monitoring to molecular/DNA/proteins diagnosis-the 26 use in portable and wearable scenarios is hindered by the lack 27 of suitable high performance low-voltage low-power (LVLP) 28 on-chip electronic interfaces [1]-[7]: designs [1], [2] use 29 discrete components; [3]-[5] present high power and area con-30 sumption; [1], [5], [6] are single-channel, not being capable 31 of recovering the real and imaginary components of the 32 impedance under test. In addition, the trend towards the 33