A 160 dB equivalent dynamic range auto-scaling interface for resistive gas sensors arrays

In this paper an integrated wide-dynamic-range interface circuit for resistive gas-sensors arrays is presented. The proposed device consists of a multi-scale transresistance continuous time amplifier followed by a 13-bit incremental AID converter. The circuit selects automatically the scale to use for each measurement and includes two digital-to-analog converters for the calibration of offset and-gain of each scale. The proposed interface circuit achieves a measurement accuracy almost always better than 0.1% over a sensor resistance range of more than 5 decades [100 Omega-20 M Omega], leading to an equivalent dynamic range of about 160 dB. The chip has been realized with a 0.35 mu m CMOS technology and occupies an area of 3.1 mm(2) consuming 6 mW from a 3.3 V power supply.