The data converters are prerequisite for digital processing of analog signals. SAR ADC is preferred for their good balance between speed, area and power considerations. In this paper, we proposed a novel comparator design based on double tail architecture for an 8-bit successive approximation register analog-to-digital converter. We implemented 8 bit analog-to-digital converter contains a Successive Approximation register, Ring counter, SR-Latch, R2R Ladder type digital-to-analog convertor and a proposed novel comparator. The circuit is simulated using Predictive Technology model 70nm Technology using Tanner EDA tool. The average INL and DNL are less than 1 LSB and 1 LSB, respectively. At the sample rate of 250MHz (2GHz clock Freq) and supply voltage of 1.2V, the ADC consumed about 1.3 mW. The analog-to-digital converter using proposed comparator deign consumes less power and thus can be used in portable device.