Abstract
People would be distant from danger if having portable oximeters that can display real-time oxygen concentration values. It is particularly important for infants, serious patients, or the people who suffer sleep apnea syndrome. Traditional oximeters utilize a circuit architecture with TIA (trans-impedance amplifier) to enlarge the signal of blood pressure wave. It takes a great chip area in exchange for gain, because the AC signal is only about 1% to 2% of the DC signal. The circuit also utilizes bandpass and lowpass filters to obtain AC and DC signal components, therefore, it needs more external capacitors that increase the module area and cost. In this thesis, the pulse oximeter and the LED current drive are integrated in standard TSMC 0.35um CMOS technology. Owing to replacing the traditional TIA with a 3T active pixel sensor structure and using comparators and switches to obtain the information of oxygen concentration, not only the number of external capacitors is reduced but also the module size is shrunk. In the experiments, the blood pressure wave signal obtained at the output of photo sensing circuit provides not only heartbeats but also breathing information. Making good use of this circuit architecture can certainly expand the fuction of products in the future.