A Wide-Range and High-Resolution Detection Circuit for MEMS Gas Sensor

In this paper, a gas detection circuit for MEMS gas sensor is presented, which has a wide measurement range and high resolution to fulfill an MEMS gas sensor. The circuit has been designed in a 0.18-μm complementary metal-oxide- semiconductor technology with a 1.8-V power supply based on resistance-to-frequency technology and occupies an area of 0.83 × 1.2 mm2. Experimental results show that the chip achieves a resistance measurement range almost over 8.5 decades (1 Ω-500 MQ) corresponded to the output frequency range from 4.11 MHz to 145 Hz which can greatly meet the performance of the MEMS gas sensor. By combining the chip with the MEMS gas sensor, the system can accurately detect various gases, including hydrogen (H2), ammonia (NH3), and alcohol (C2H5OH), even at low concentration (<;0.4 ppm), and the output frequency has a very good linear relationship with the gas concentration.