An Analog Front-End Circuit for CO2 Sensor Readout in 0.18-µm CMOS Process

An analog front-end (AFE) trans-impedance amplifier (TIA) for CO
₂
detector is presented. It senses the current generated from the IR detector, which contains the information of the CO
₂
concentration in the air. An automatic IR sensor baseline current calibration loop is proposed to cancel the diode DC current and amplify only the desired signal. The prototype is implemented in the 0.18-μm CMOS process. The measurement is performed with an off-chip resistor with voltage input, emulating the IR detector. It consumes 3.38 mW (including calibration) with 62.4-dB SNR over 1-kHz BW and achieves 0.16 ppm resolution.