Approximate Sum-of-Products Designs Based on Distributed Arithmetic

Approximate circuits provide high performance and require low power. Sum-of-products (SOP) units are key elements in many digital signal processing applications. In this brief, three approximate SOP (ASOP) models which are based on the distributed arithmetic are proposed. They are designed for different levels of accuracy. First model of ASOP achieves an improvement up to 64% on area and 70% on power, when compared with conventional unit. Other two models provide an improvement of 32% and 48% on area and 54% and 58% on power, respectively, with a reduced error rate compared with the first model. Third model achieves the mean relative error and normalized error distance as low as 0.05% and 0.009%, respectively. Performance of approximate units is evaluated with a noisy image smoothing application, where the proposed models are capable of achieving higher peak signal-to-noise ratio than the existing state-of-the-art techniques. It is shown that the proposed approximate models achieve higher processing accuracy than existing works but with significant improvements in power and performance.