研究目的
To compare three configurations of ISFET arrays fabricated in unmodified CMOS for chemical imaging with linear pH-to-output conversion, identifying the relative merits and limitations of each approach.
研究成果
The current-mode approach results in the best overall performance for linear pH-to-output sensing, as quantified by a defined figure-of-merit. However, the best designs are application-specific, and the study serves as a reference for future ISFET array designs.
研究不足
The study does not optimize the designs for speed, and the voltage-mode pixels are slower due to their biasing currents. The noise performance is dominated by chemical noise, and the designs are not universally optimal but application-specific.
1:Experimental Design and Method Selection:
The study compares three ISFET array configurations (voltage-mode source-follower, current-mode in velocity saturation, and current-mode with programmable-gate capacitor) fabricated on the same chip.
2:Sample Selection and Data Sources:
The arrays are tested using in-house prepared pH buffers (pH 4, 7, and 10) to measure pH sensitivity and other performance metrics.
3:List of Experimental Equipment and Materials:
The chip is fabricated in the AMS
4:35μm 2P4M process, and testing involves a peristaltic pump for solution flow, a high precision data acquisition unit (PowerLab 8/35, ADInstruments), and an oscilloscope (LeCroy WaveSurfer 434). Experimental Procedures and Operational Workflow:
The arrays are characterized for linearity, speed, power consumption, size, attenuation, and noise. The pH sensitivity is measured by flowing different pH buffers over the chip and recording the output.
5:Data Analysis Methods:
The input-referred noise is calculated from power spectral density measurements, and a figure-of-merit is defined to compare the overall performance of each configuration.
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