Threshold Inverter Quantizer (TIQ) based ADC with thermometer code is proposed in the literature as an alternative to traditional flash ADC for low power applications. TIQ based ADC suffers from threshold variations due to process. In this paper, a novel TIQ based ADC with gray code is proposed.The architecture is also made tolerant to the process variations. For the purpose of evaluating its efficacy, a 4-bit ADC using the proposed technique is implemented in UMC 0.18μm CMOS technology at a supply voltage of 1 V and studied through simulation. The proposed ADC achieves a maximum sampling rate of 300 MS/s for an input signal with 1 V swing and has a power consumption of 122 μW. The power dissipated by the proposed ADC is lower compared to those reported in the literature. The proposed ADC exhibits INL of 0.0622 LSB, DNL of 0.0444 LSB, SNDR of 25.227 dB and ENOB 3.89 bits respectively. It has a better FoM of 0.027 pJ/conversation step. The proposed scheme reduces the deviation of the inverter threshold by 98.75% compared to that of normal inverter. © 2015 IEEE.