Oxide TFT Frontend Amplifiers for Flexible Sensing Systems

作者：Xu, Yuming; Wu, Zhaohui; Li, Bin^*; Deng, Sunbin^*; Zhong, Wei; Li, Guijun; Luo, Dongxiang; Yeung, Fion Sze Yan; Kwok, Hoi Sing; Chen, Rongsheng^*

来源：IEEE Transactions on Electron Devices, 2021, 68(12): 6190-6196.

DOI：10.1109/TED.2021.3120023

• Frontend amplifier
• heart-rate measurement
• metal-oxide thin-film transistors (TFTs)

This article presents a frontend amplifier based on the 50-mu m channel length n-type only indium-tin-oxide (ITO)-stabilized ZnO thin-film transistors (TFTs) on glass substrate. The amplifier has an external-bias ac-coupled, open-loop capacitor bootstrap structure. The area and power consumption are 41 mm(2) and 0.1 mW (8-V supply), respectively. Electrical measurement results show a gain of 20 dB, a bandwidth of 3 Hz-6 kHz, a common-mode rejection ratio (CMRR) up to 42 dB, an input impedance of 100 M Omega, and an input-referred noise of 106 mu V-rms (integrated from 1 to 200 Hz). The noise efficiency factor (NEF) and power efficiency factor (PEF) of the amplifier are, respectively, 248 and 4.9 x 10(5), which is comparable among the state of the arts. The amplifier is successfully used to measure the heart-rate signal, which demonstrates its practicality.