Low-Power Organic Light Sensor Array Based on Active-Matrix Common-Gate Transimpedance Amplifier on Foil for Imaging Applications

Abstract

This article presents a 57.6- $\mu \text{W}$ mechanically flexible active-matrix imaging system based on a $4\times 5$ array of light sensors, each composed of a photodetector (PD) using a light-sensitive organic polymer and a transimpedance amplifier (TIA) based on organic thin-film transistors and integrated thin-film carbon resistors. The PDs and the electronics are fabricated on separate plastic films and integrated into a system. Two different topologies for the TIA are designed, implemented, and characterized. The first topology is a self-biased TIA based on a gain-boosted operational amplifier (op-amp), providing an open-loop dc gain of 41.3 dB. This op-amp-based TIA, with a feedback resistor, provides stable current-to-voltage conversion (0–100 $\mu \text{A}$ and 2.0–3.7 V) at frequencies up to 300 Hz. The second topology is a low-power gain-boosted common-gate (GB CG) TIA that performs current-to-voltage conversion with a nonlinearity as small as ±0.3% within a bandwidth of 1 kHz. The output voltages of the light sensors are read and converted into a $4\times 5$ pixel gray-scale image displayed on a computer monitor to visualize the functionality of the system.