A Stability-Enhanced Feedback-Based Readout Circuit for Active-Matrix Resistive Sensor Arrays

초록

Active-matrix (AM) resistive sensor arrays are widely used because they suppress the crosstalk currents that plague passive matrices. In conventional feedback-based readout circuit (FBROC), the static voltage-drop error across the pixel switch is cancelled; however, as the pixel-transistor on-resistance (R<inf>ON</inf>) is increased to shrink switch size and raise pixel density, parasitic capacitances push the feedback loop’s poles to lower frequencies, degrade phase margin, and induce oscillation—producing large sensing errors and limiting accuracy. This work proposes a stability-enhanced FBROC that augments the conventional architecture with a single RC compensator placed outside the array. The compensator introduces tunable zeros in the loop transfer function, restoring phase margin and suppressing oscillation without any in-pixel modification. Simulation and measurement results show that the proposed FBROC maintains a phase margin greater than 50° and reduces R<inf>ERROR</inf> from 1393.2% to less than 0.1% under worst-case conditions. The allowable R<inf>ON</inf> increases by a factor of ten, enabling smaller pixel switches (higher pixel density) and scaling to larger row/column counts while keeping higher accuracy despite increased parasitic capacitances. Because the compensator is passive and placed outside the array, the approach is simple, area-efficient, and compatible with existing AM sensor array implementations—breaking the device-size/loop-stability trade-off and supporting higher-resolution resistive sensing. © 2001-2012 IEEE.

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