Turkish Journal of Electrical Engineering and Computer Sciences




The compute-intensive multimedia applications on portable devices require power and area efficient arithmetic units. The adder is a prime building block of these arithmetic units and limits the overall performance. Therefore, this paper analyzes the logic operations of the state-of-the-art adders and presents a novel low complexity adder segment with new carry prediction logic by removing the redundant logic and sharing the common operations. Further, a new power and area efficient approximate carry skip (PAEA-CSK) adder is proposed using the novel adder segment. The effectiveness of the proposed PAEA-CSK adder is evaluated and compared over the existing adders by implementing them in VHDL and synthesizing using the Synopsys Design Compiler with the 65nm TSMC CMOS Library. The synthesis result shows that the proposed PAEA-CSK adder requires $27.28\%$ and $18.03\%$ less area and power, respectively, over the existing carry skip-based approximate adder with the same accuracy. Further, the Sobel edge detector (SED) embedded with the proposed adder improves PSNR by a minimum of 16.94 dB over the SED embedded with a nonzeroing bit-truncation adder.

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