Design of a wideband CMOS impedance spectroscopy ASIC analog front-end for multichannel biosensor interfaces

Dual-mode CMOS analog front-end (AFE) for electrical impedance spectroscopy (EIS) systems

This paper presents the operation of a dual-mode wideband CMOS analog front-end (AFE) for electrical impedance spectroscopy. The chip combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar EIS analysis. The chip addresses the need for flexible readout units for real-time simultaneous single-cell and large scale tissue/organ analysis. Postlayout simulations show that the VR channel is capable of wideband operation up to 12 MHz with noise floor as low as 16.4 nV/Hz1/2. A 2-bit control allows to select between a high-frequency low-gain channel and a bandwidth-limited high-gain channel. Each VR channel occupies an area of 0.48 mm2. The CR channel is capable of 80 dB of dynamic range, by converting currents between 1 nA to 10μA, while achieving a noise floor of 1.4 pA/Hz1/2. An automatic gain control (AGC) unit can be enabled in order maintain the sensor signal within the ADC dynamic range. Each CR channel occupies an area of 0.21 mm2. The chip consumes between 290 μA and 690 μA per channel and operates from a 1.8 V supply. The chip will be part of a fully flexible and configurable dual-mode EIS systems for impedance sensors and bioimpedance analysis.

Wideband Fully-Programmable Dual-Mode CMOS Analogue Front-End for Electrical Impedance Spectroscopy

This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer detection, imaging and characterization. The chip, implemented in a 180-nm CMOS technology, combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar electrical impedance spectroscopy (EIS) analysis. Each VR channel occupies an area of 0.48 mm 2 , is capable of an operational bandwidth of 8 MHz and a linear gain in the range between -6 dB and 42 dB. The gain of the CR channel can be set to 10 kΩ, 50 kΩ or 100 kΩ and is capable of 80-dB dynamic range, with a very linear response for input currents between 10 nA and 100 μ A. Each CR channel occupies an area of 0.21 mm 2 . The chip consumes between 530 μ A and 690 μ A per channel and operates from a 1.8-V supply. The chip was used to measure the impedance of capacitive interdigitated electrodes in saline solution. Measurements show close matching with results obtained using a commercial impedance analyser. The chip will be part of a fully flexible and configurable fully-integrated dual-mode EIS system for impedance sensors and bioimpedance analysis.