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This work presents a low power ECG interface for wearable applications, based on unipolar a-IGZO TFTs manufactured on a flexible substrate. The interface consists of a cascaded diode-connected load preamplifier followed by a reset integrator, which is used to convert the voltage signal to a pulse-width modulated (PWM) representation. The output is thus provided as a binary PWM waveform, which can be conveniently sent to a reader device using wireless communication and can be further converted to a digital representation using a simple counter. The flicker noise and the offset are eliminated using an approach similar to correlated double sampling. An input chopper is exploited to alternate the connection between the inputs of the preamplifier for each sample. The output signal is then extracted by subtracting two consecutive samples after conversion to the digital domain. In this way offset and low-frequency noise, which are correlated between the two samples, are effectively cancelled.

Amorphous IGZO (a-IGZO) TFTs fabricated on flexible large-area substrates provide better mobility than a-Si or organic counterparts and good uniformity. These features make a-IGZO TFTs an attractive technology for large-area sensing (e.g. strain, pressure, IR), low-cost RFIDs augmented with sensors and monitoring of biopotentials. In this context, it is crucial to accurately transform analogue sensor signals in a robust representation. The most common choice is a synchronous digital word, but a two-level PWM representation is another interesting possibility. Binary PWM can be transmitted on wire or via RF amplitude modulation with high immunity to noise and interferers.

Our goal is to create thin low-cost flexible NFC tags to allow everyday objects to communicate to smartphones and computers and thus participate in the Internet of Things. We employ amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor circuits processed at low temperatures, less than 250C, directly on thin polyester substrates. Reaching NFC standards with a-IGZO circuits is challenging because the technology is n-type only and the electron mobility (∼15cm7Vs) is lower compared to silicon. As the main result, we show that the most important NFC regulatory standards are met, even with relaxed 5 micron design rules, using optimized design topologies.

In this paper, we present some of the technology challenges and process temperature trade-offs when realizing AM OLED displays on thin flexible plastic films that can be mechanically bent to a roll radius of ∼1 cm. We furthermore present complementary approaches to realize low-power, high resolution OLED displays using self-aligned IGZO TFT architecture; a novel driving method using a compact 2T-1C pixel engine. cop. 2014 JSAP.