Mostly Passive Δ - Σ ADC with a-IGZO TFTs for Flexible Electronics

This paper presents a novel mostly passive Δ-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-number-of-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.