A Novel Method for Scalable VLSI Implementation of Hyperbolic Tangent Function

Hyperbolic tangent and Sigmoid functions are used as non-linear activation units in the artificial and deep neural networks. Since, these networks are computationally expensive, customized accelerators are designed for achieving the required performance at lower cost and power. The activation function and MAC units are the key building blocks of these neural networks. A low complexity and accurate hardware implementation of the activation function is required to meet the performance and area targets of such neural network accelerators. Moreover, a scalable implementation is required as the recent studies show that the DNNs may use different precision in different layers. This paper presents a novel method based on trigonometric expansion properties of the hyperbolic function for hardware implementation which can be easily tuned for different accuracy and precision requirements.