A Low Power Time Domain ECG Interface Based on Flexible a-IGZO TFTs

Abstract

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 pulsewidth 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 lowfrequency noise, which are correlated between the two samples, are effectively cancelled.

Review of recent trends in flexible metal oxide thin-film transistors for analog applications

“…In-vivo experiments were performed using two gel electrodes in contact with the forearm and elbow of a patient, measuring an EMG amplitude of 1.6 mV (see figure 8(b)). On the other hand, an interface for monitoring the heart rate was fabricated using a pre-amplifier (figure 6(e)) in combination with a reset integrator and a comparator [168,169]. The systems, characterized in the best case by a power consumption as low as 26.25 µW, a surface area of 19.5 mm 2 and a supply of 10 V, were successfully employed to measure reconstructed [169] and in-vivo heartbeat [168].…”

“…On the other hand, an interface for monitoring the heart rate was fabricated using a pre-amplifier (figure 6(e)) in combination with a reset integrator and a comparator [168,169]. The systems, characterized in the best case by a power consumption as low as 26.25 µW, a surface area of 19.5 mm 2 and a supply of 10 V, were successfully employed to measure reconstructed [169] and in-vivo heartbeat [168]. Metal oxide analog circuits are often used as readout for imaging reconstruction.…”

“…In a future influenced by the Internet of Things (IoT), artificial intelligence, smart assistance systems, supportive electronics collecting and processing data will be present in nearly all facets of our society [1][2][3]. Although such visions are typically associated with a digital society, a significant driving force behind these developments are specialized analog systems capable to transmit and receive data [4], condition sensors' parameters [5,6], drive actuators [7,8], and/or harvest and control power [9]. Nowadays it is widely accepted that electronic thin-film circuits fabricated on soft and large-area substrates represent a very promising technological platform to realize costefficient systems that can be unobtrusively integrated into our environment [4,10,11].…”

Domiciliary Hospitalization through Wearable Biomonitoring Patches: Recent Advances, Technical Challenges, and the Relation to Covid-19

“…It is worth mentioning that even though low power ECGs are available [173], ECG communication is generally power-hungry. In contrast to the heart rate, or respiration rate, that require sending the data at ~1 Hz, a full ECG requires digitizing the ECG curves and send data at a much higher rate.…”