A monolithic interface circuit for gas sensor arrays:: Control and measurement

The electronics for monolithically integrated gas sensor arrays fabricated using a compatible CMOS process have been developed. Circuitry includes the heater driver for temperature control and an interface circuit for inspection of the four sensors in the array. The operating temperature of the sensing resistors is between 200degrees and 400degreesC. The proposed temperature controller is capable of regulating the temperature of a 2100 x 2100 mum hotplate up to 400degreesC with a resolution of 2degreesC with 5 V supply voltage. A readout circuit based on a ring-oscillator has been included to measure the sensing resistance change upon gas exposure over a high dynamic range. Because it is robust, small, low priced and offers future capabilities with adequate signal processing, the system would be able to cover most of today's gas sensor markets.