ISFET Pixel Array With Selectable Sensitivity and Bulk-Based Offset-Drift Nullification Capability for Reduction of Non-Ideality Effects

This article presents a monolithic, cost-effective, label free, low power, robust $3\times2$ fully differential ion-sensitive field-effect transistor (ISFET) pixel array aimed at pH sensing. Each is based on readout architecture which eliminates need for additional non-ideality compensation circuitry. Additionally, the design offers capability to correct residual drift and trapped charge offset through substrate-based voltage adjustment during calibration. The also provides unique ability selecting sensitivity according desired mode of operation has not been demonstrated previously. We present experimental results obtained from fabricated in an unmodified AMS notation="LaTeX">$0.35~\mu \text{m}$ CMOS process using 3.3 V power supply. demonstrates 61 mV/pH when operated high 25 rejection over entire range, with remove already small 0.3 mV/min any mismatch by adjusting substrate voltage.