Key result
TFT-based PPG acquisition circuit achieves ~80-dB ADC dynamic range with stable performance across temperatures.
Why the study?
Limited performance, process variation, and motion artifacts hinder the adoption of thin-film transistor devices on flexible substrates for seamless, long-term wearable health monitoring.
The proposed TFT-based PPG acquisition circuit demonstrates improved linearity and robustness, providing a feasibility demonstration for fully integrated flexible electronics in wearable bio-signal monitoring.
Answers are grounded in this paper and cite their sources.
Advances flexible wearable PPG feasibility; leaves open clinical validation for cardiovascular monitoring.
Thin-film transistor (TFT) can be fabricated on flexible substrates, offering potential for seamless, long-term wearable health monitoring. However, the limited performance, process variation, and motion artifacts hinder the widespread adoption of flexible wearable devices. This article presents a TFT-based photoplethysmography (PPG) acquisition circuit for flexible healthcare rings, integrating a voltage-controlled oscillator (VCO) based analog front-end (AFE) to overcome the performance limitations caused by the low mobility of TFT devices. Meanwhile, a dead-zone free (DZ-Free) phase-frequency detector (PFD) was proposed and integrated into the VCO transimpedance amplifier (TIA) to enhance the linearity. Additionally, a 0-1 MASH VCO-analog-to-digital conversion (ADC) structure was adopted to improve the quantization dynamic range (DR). The system is implemented using <tex-math notation="LaTeX">3-</tex-math> <tex-math notation="LaTeX">μ</tex-math> m low-temperature poly-silicon (LTPS) TFT (LTPS-TFT) process of TIANMA Microelectronics. The measurement results show that DZ-Free PFD improves the linearity and the proposed VCO-TIA achieves a 61.5-dB DR. The proposed ADC demonstrates a 72-dB spurious-free dynamic range (SFDR), a 65.8-dB SNDR and an 80-dB DR. Under temperature sweeping from <tex-math notation="LaTeX">-40~ ~∘C</tex-math> to <tex-math notation="LaTeX">80~ ~∘C</tex-math> and supply voltage variations of <tex-math notation="LaTeX">10~± ~2</tex-math> V, the ADC maintains performance variations within 3%, while the TIA stably sustains a gain of 110 dB <tex-math notation="LaTeX">Ω</tex-math> . Finally, PPG and blood oxygen saturation ( <tex-math notation="LaTeX">SpO_2</tex-math> ) measurements were demonstrated, including ambient light compensation. This work provides a feasibility demonstration for TFT-based fully integrated flexible electronics in bio-signal monitoring applications.
No takes yet. Share an insight, caveat, or question.
Zhang et al. (2025) studied this question. TFT-based PPG acquisition circuit was evaluated on Dynamic range and performance stability. The proposed TFT-based PPG acquisition circuit achieved a 61.5-dB dynamic range for the VCO-TIA and an 80-dB dynamic range for the ADC, maintaining stable performance across temperature variations.
Synapse has enriched 10 related papers. Consider them for comparative context: