Samira Sorayaasa and Majid Ahmadi, University of Windsor, Canada

Hyperbolic tangent (Tanh) activation function is used in multilayered artificial neural networks (ANN). This activation function contains exponential and division terms in its expressions which makes its accurate digital implementation difficult. In this paper we present two different approximation techniques for digital implementation of Tanh function using power of two and coordinate rotation digital computer (CORDIC) methods. A comparative study of both techniques in terms of accuracy of their approximations in hardware costs as well as their speed when implemented on FPGA is also explained

ANNs, Tanh, activation function, approximation with power of two, CORDIC algorithm, FPGA, optimization, hardware resource, latency, error.