A Sub-nW Temperature Invariant Voltage Reference in a Unipolar TFT-based Flexible IC Technology

Voltage reference circuits are crucial for any mixed-signal circuits, providing PVT (Process, Voltage, Temperature) robust output for the system's stability and accuracy. This paper presents a novel voltage reference circuit implemented in an indium gallium zinc oxide (IGZO) based thin film transistors (TFT) technology, proposing for the first time a sub-nanowatt, area-efficient circuit realized with only a single N-type TFT in a 600 nm technology. The design occupies a minimal area of 27x37 μm2, operates across a broad supply voltage range from 0.5 V to 3 V, and maintains functionality from 0 °C to 100 °C. The circuit has an ultra-low power consumption between 0.75 nW to 1.2 nW while achieving an output voltage of 454 mV with a temperature coefficient (TC) as low as 28.9 ppm/°C. The simulated results, which include process variation, temperature dependence, line sensitivity and power supply rejection ratio measurements, underline the circuit's potential for high-efficiency, low-power applications in next-generation flexible electronics.