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This paper presents sixth-order fully differential active low pass RC and switched-capacitor (SC) filters using N-type IGZO thin-film transistors for flexible wearable continuous health monitoring systems. As a first step, a low-gain amplifier using a diode-connected load and a fully differential amplifier is designed with positive feedback based on capacitor bootstrapping. These amplifiers present a gain around 5.03 and 40 dB, respectively, whereas their respective GBW product are around 450 and 200 kHz. Then these amplifiers are employed to realize biquads, with which a sixth-order Sallen-Key lowpass RC and SC filters are implemented. The SC filter realized with low-gain DDA has shown a simulated THD of −30.9 dB, SFDR of 30.1 dB, and a power consumption of 456 μW. On the other hand, the SC filter presents a THD of −31.4 dB, SFDR of 32.2 dB, and a power consumption of 573 μW with highgain differential difference amplifier (DDA) when a power supply of 10 V is used. Circuit simulations have been carried out in Cadence Virtuoso using in-house IGZO TFT models. KEYWORDSactive RC filters, differential amplifier and health monitoring system, IGZO TFT, switched capacitor filters 1 | INRODUCTION Continuous health monitoring of post hospitalized cardiac patients is vital. In present scenario, most of the cardio vascular system activities are being monitored using ECG and BP measurements using cuffs, which limit the mobility of the patients and need human interaction. Nevertheless, few wearable devices were reported with standard CMOS technology, 1-4 where these systems are bulky (due to the battery weight), rigid, and expensive. In order to get rid of these drawbacks and to guarantee user comfort, biomedical self-contained wearable systems implemented with low-cost flexible electronics would be a perfect solution, where circuits can be driven by printed batteries. 5,6 Among other semiconductor technologies (a-Si: H TFT and organic TFT) that allow flexible electronics due to compatibility with low-temperature fabrication (≥150°C), 7,8 amorphous indium gallium zinc oxide thin-film transistors

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This paper presents a novel mostly passive ∆-Σ ADC using amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs). The ADC circuit consists of passive elements (resistors and capacitors), a novel dynamic comparator, a D-Flip Flop and a pseudo-CMOS BS inverter. In-house oxide TFT model is used for circuit simulations in Cadence environment. The proposed ADC results in effective-numberof-bits (ENOB) of 11.2 bits and a figure-of-merit (FOM) of 0.15 µJ/conversion step at 2 kHz sampling frequency with a 10 V power supply. This circuit would find potential applications in biomedical wearable systems, in which, the ADC is probably the most important block.