The Impact of Device Uniformity on Functionality of Analog Passively-Integrated Memristive Circuits

Passively-integrated memristors are the most prospective candidates for designing high-speed, energy-efficient, and compact neuromorphic circuits. Despite all the promising properties, experimental demonstrations of passive memristive crossbars have been limited to circuits with few thousands of devices until now, which stems from the strict uniformity requirements on the IV characteristics of memristors. This paper expands upon this vital challenge and investigates how uniformity impacts the computing accuracy of analog memristive circuits, focusing on neuromorphic applications. Specifically, the paper explores the tradeoffs between computing accuracy, crossbar size, switching threshold variations, and target precision. All-embracing simulations of matrix multipliers and deep neural networks on CIFAR-10 and ImageNet datasets have been carried out to evaluate the role of uniformity on the accuracy of computing systems. Further, we study three post-fabrication methods that increase the accuracy of nonuniform 0T1R neuromorphic circuits: hardware-aware training, improved tuning algorithm, and switching threshold modification. The application of these techniques allows us to implement advanced deep neural networks with almost no accuracy drop, using current state-of-the-art analog 0T1R technology.