Temperature Detection System Using Oxide TFTs on a Flexible Substrate

This article presents a compact temperature detection system using amorphous-InGaZnO thin-film transistor (TFT) technology. The proposed system is fabricated on a 30-
$\mu \text{m}$
-thick polymide substrate. This system consists of a temperature readout circuit together with a novel high-performance clocked comparator. Individual blocks and the complete system have been characterized from measurements at a low-power supply voltage of 3 V and a load of 10
$\text{M}\Omega ||12$
pF. The measured sensitivity of the temperature readout circuit is 16 mV/°C. On the other hand, the comparator is capable of discriminating a minimum differential input voltage (
$V_{\text {in}\min }$
) of 30 mV and showing the input referred noise of 5 mV at an input signal frequency (
$f_{\text {in}}$
) of 10 kHz. The circuit is showing a reliable operation up to an
$f_{\text {in}}$
of 22.5 kHz with a slight degradation in the output voltage swing. This circuit shows a propagation delay of
$3~\mu \text{s}$
and a power consumption of
$48.15~\mu \text{W}$
from measurements. The complete system is able to discriminate a temperature variation down to 2 °C. This system would find potential application in biomedical wearable devices for temperature detection.