Design of 150-μV input-referred voltage 1-GHz comparison frequency dual offset cancelation comparator for pH biomarker system-on-chip

The highlight of in vivo or ex vivo measurement to monitor the pH value from blood or saliva is emerging in these years since changes in pH suggest that hidden diseases are about to occur. In this paper, we design and implement a SoC for pH measurement, and a dual offset cancelation technique in comparator featured with 150-uV input referred voltage and 1-GHz comparison bandwidth is verified. The SoC by utilizing proposed dual offset cancelation technique can sense 8 femto farad capacitance change in the deionized water, 12 femto farad change in the glucose liquid, and 14 femto farad in the 0.5% hydrochloric acid. The SoC for pH measurement is not only used to detect pH change in blood or saliva, but can also extend to wearable device to monitor human's biomarkers such as pH and Na+ in sweat to prevent the disease in advance.