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

Abstract

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.

Rapid and Direct Detection of Trimethylamine N-oxide Using an Off-Chip Capacitance Biosensor with Readout SoC for Early-Stage Thrombosis and Cardiovascular Disease

“…The spacing between the sensing line and other lines is 40 μm, and the trace parasitic capacitance is estimated using eq . Given that the sensing frequency from our laboratory-owned SoC is 10 MHz (corresponding to a period width of 0.1 μs), and the calculated RC time constant based on eqs and is 1.3 × 10 –12 s, the chip can effectively handle the resistance and capacitance loading of the proposed off-chip sensor. Our laboratory-designed SoC is specialized in detecting subtle changes in capacitance down to 1 × 10 –18 farad. R = ρ × L A = 2.8 × 10 − 8 × 60 × 10 − 6 × 114 760 × 10 − 9 × 20 × 10 − 6 = 12.9 0.25em normalΩ where ρ is the Mo/Al/Mo film resistivity (μΩ cm); L is the sensing line length; and A is the cross area of the sensing line. C = W × L × e 0 × e r d = 20 × 10 − 6 × 40 × 10 − 6 × 160 × 8.85 × 10 − 12 × 3.5 40 × 10 − 6 = 99.2 0.25em fF where W is the sensing line width; L is the sensing line trace; e 0 is the air dielectric constant = 8.85 × 10 –12 F/m; e r is the SiO x dielectric constant = 3.5.…”