Temperature Control Circuit for Gas Sensor

This paper presents a Temperature Control Circuit for a microhotplate based gas sensor fabricated in standard 0.35/0.18μm CMOS technology. The on-chip microhotplate provide very high temperatures (between 200oC and 400oC), which are necessary for the normal operation of metal oxide sensing layers. The complete temperature control circuit comprises of 10-bit A/D converter, low pass filter, two 10-bit D/A converters, two operational amplifiers and a digital controller (Vertex-IV FPGA). The required temperature is achieved by sourcing suitable amount of current to the gas sensor through a current steering 10-bit.DAC.