A signal processing ASIC for an electronic nose

This paper describes the development of a multi-channel BiCMOS ASIC that is capable of measuring absolute and changes in resistance. As such it is used for interrogating sensors based on resistive arrays. The AS1C was initially developed as part of an integrated electronic nose based on conducting polymers. The integrated nose is a hybrid constructed on a multi-layer, thick-film ceramic substrate. At one end, an array of 32 pairs of exposed gold electrodes surround 3 sides of a ground plane. Each electrode measures 1 mm×0.25 mm, they are separated by 0.25 mm and are shorted in pairs by conducting polymers. Each electrode is routed back to the 84-pin Application Specific Integrated Circuit (ASIC) which is the subject of this paper. The chip was designed in-house, and fabricated by SGS-Thomson in a 2 μm BiCMOS process under the EUROCHIP initiative