1. Signal and Noise Analysis of an Open-Circuit Voltage Pixel for Uncooled Infrared Image Sensors
- Author
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Waleed Khalil, Gamini Ariyawansa, Ramy Tantawy, Sanjay Krishna, Christopher D. Taylor, Earl Fuller, Phillip Van Hooser, Zahra Taghipour, Teressa Specht, Theodore J. Ronningen, Roman Fragasse, D.S. Smith, Charles J. Reyner, and Josh Duran
- Subjects
Physics ,Pixel ,Physics::Instrumentation and Detectors ,Subthreshold conduction ,Dynamic range ,Noise (signal processing) ,Topology (electrical circuits) ,Photodiode ,law.invention ,CMOS ,law ,Electronic engineering ,Sensitivity (control systems) ,Electrical and Electronic Engineering - Abstract
An imaging pixel unit-cell topology leveraging a photodetector in the forward-bias region is proposed. Connecting the anode of the photodiode to the gate of a NMOS device operating in the subthreshold region provides the basis for a new open-circuit voltage pixel (VocP) architecture. Theoretical analysis is presented to show the response and performance benefits of the VocP in comparison to a conventional pixel. Based on this analysis, the signal and noise relationships for both pixels are derived and leveraged to construct an end-to-end readout system model. The model results highlight potential performance benefits of the VocP over a conventional direct-injection pixel topology. To verify the analysis, the proposed VocP readout architecture is fabricated along with a conventional direct-injection pixel readout in a $0.18~\mathrm {\mu }\text{m}$ CMOS technology. The VocP performance is compared to a traditional reverse-bias current-mode photodetector configuration. Simulation, modeling, and measurements align with the proposed analytical model. Benefits in system sensitivity and dynamic range are demonstrated showing more than a $2\times $ improvement in noise-equivalent temperature difference and a 4 dB improvement in dynamic range.
- Published
- 2021
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