Aiming at the problems of low sensitivity and long response time of non-dispersive infrared CH₄ gas sensor, a CH₄ gas sensor based on photoconductive principle is designed. The sensor is mainly composed of PbSe photoconductive infrared detector, signal processing circuit, light source driving circuit and light path gas chamber. By analyzing the relationship between gas concentration and detector output signal, the concentration output relationship equation is fitted to realize the detection function. Through experiments, gases with different concentrations are detected at room temperature. The results show that the output error, minimum detection limit, minimum response time and other parameters of the sensor are good, and the gas can be effectively measured in the range of 1000 cm³/m³.

Aiming at the problem that the traditional dynamic element matching(DEM) method needs more hardware resources, a second-order error feedback noise-shaping SAR ADC is designed. The design uses segmented capacitors to reduce the size of DAC array and the capacitance of error feedback loop, and reduce the area of the whole circuit. On this basis, a DEM method applied to segmented capacitor array is formed, which reduces the influence of capacitor mismatch on performance parameters such as signal-to-noise-distortion ratio(SNDR) at the cost of fewer additional circuit components. The simulation results show that the designed noise-shaping SAR ADC can achieve 70.9 dB SNDR with an 8-bit capacitor array with a capacitance mismatch of 0.3%, and the required area is only 0.019 mm².