Nonvolatile Low-Cost Approximate Spintronic Full Adders for Computing in Memory Architectures

In this article, four novel approximate full-adder (AXFA) circuits based on the emerging magnetic tunnel junction (MTJ) device is proposed. The proposed magnetic FAs (MFAs) offer full nonvolatility, low area, and considerably lower energy consumption than their previous counterparts. Also, two of the proposed MFAs have the advantage of single event upset (SEU) tolerance. Simulation results reveal that the proposed designs offer over 50% energy efficiency in comparison with the considered previous fully nonvolatile MFAs. Using the proposed adders in the design of an approximate Gaussian filter, we showed that the filtered noisy images have almost the same results as the accurate Gaussian filter. The proposed MFAs have an accurate carry-out output and an approximate sum output with an error distance of 2.