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 A/D 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 Ω – 20 MΩ], leading to an equivalent dynamic range of about 160 dB. The chip has been realized with a 0.35 µm CMOS technology and occupies an area of 3.1 mm^2 consuming 6 mW from a 3.3 V power supply.