paper

 A 128×128 Current-Mode Ultra-High Frame Rate ISFET Array for Ion Imaging

Publication Date:
Publication Date
4 May 2018
Author(s)
Junming Zeng; Nicholas Miscourides; Pantelis Georgiou

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Abstract

This paper presents a 128 × 128 ISFET array with current mode readout peripherals for real-time ion imaging. Current-mode operation is employed to achieve very high speed and frame rate and provide a linear mapping between the ion concentration at the sensing layer (typically hydrogen ions - pH) to the drain current of the device. To this effect, a single device biased in the triode region can serve as both the sensing and readout device in the pixel ensuring a very small area footprint per pixel. Compensating for known non-ideal effects of the ISFET, namely trapped charge and drift, is implemented by resetting the gate voltage whereas any additional circuit offsets are eliminated by auto-zeroing. Auto-zeroing and sampling takes place on a row-parallel basis which is then multiplexed to 8 current mode ADCs. The chip is designed in a standard 0.35um CMOS process, occupies an area of 2.6mm × 2.2mm and can achieve a frame rate of 3000 fps which is the highest in this process node. We anticipate that the proposed system will increase the current temporal limit of detection of chemical reactions and provide new insight into real-time ion dynamics.

Description

J. Zeng, N. Miscourides and P. Georgiou, "A 128×128 Current-Mode Ultra-High Frame Rate ISFET Array for Ion Imaging," 2018 IEEE International Symposium on Circuits and Systems (ISCAS), 2018, pp. 1-5, doi: 10.1109/ISCAS.2018.8351178.