This paper presents a low-power ethanol sensing read-out circuit using amorphous-Indium-Gallium-Zinc-Oxide thin-film transistors (a-InGaZnO TFTs). The read-out circuit is implemented with a proposed low-power high-speed ring oscillator (RO). The proposed RO employs bootstrapped pseudo-CMOS inverter, whose delay and power are reduced by using intermediate signals generated within the RO, hence, ensuring the high frequency of oscillations and low-power consumption. This design further ensures improved sensitivity of the read-out circuit. To validate the proposed idea, 9-stage conventional low power and proposed ROs have been designed and simulated using in-house a-InGaZnO TFT models at a supply voltage of 8V. Simulation results show that the proposed RO provides 11.8% improvement in the frequency of oscillations and 18.5% reduction in power consumption compared to the conventional design. Further, the proposed circuit has shown an improvement of 9% in the sensitivity compared to the conventional design. Therefore, this circuit finds potential application in read-out sensing systems.