In this paper, we present the analog circuit design and implementation of an adaptive neuromorphic olfaction chip. An analog VLSI device with on-chip chemosensor array, on-chip sensor interface circuitry and on-chip learning neuromorphic olfactory model has been fabricated in a single chip using Austria Microsystems 0.6 mu m CMOS technology. Drawing inspiration from biological olfactory systems, the neuromorphic analog circuits used to process signals from the on-chip odour sensors make use A temporal "spiking" signals to act as carriers of odour information. An on-chip spike time dependent learning circuit is integrated to dynamically adapt weights for odour detection and classification. All the component subsystems implemented on chip have been successfully tested in silicon.