A CMOS Citric Acid Concentration to Duty Cycle Converter with Adjustment Circuits for Detecting Citric Acid Concentration Applications

In this paper, a CMOS citric acid concentration to duty cycle converter with adjustment circuits for detecting citric acid concentration applications is newly proposed. An adjustment technique to make largest sensitivity of sensors is also proposed. After adjustment, the maximum range of input current generated by sensors is 0.1 μA to 15 mA, and its corresponding range of output duty cycle range is 11.1 to 98.99 %. The chip area is 1.49 × 1.49 mm
²
. The proposed chip is appropriate for detecting citric acid concentration in food, drinks, cosmetics, and etc. The output of the proposed chip could be easily communicated to back-end digital systems, such as mobile devices, and quickly display the information of the citric acid concentration.