Stochastic implementation of the activation function for artificial neural networks

One of the key elements in an artificial neural networks (ANNs) is the activation function (AF), that converts the weighted sum of a neuron's input into a probability of firing rate. The hardware implementation of the AF requires complicated circuits and involves a considerable amount of power dissipation. This renders the integration of a number of neurons onto a single chip difficult. This paper presents circuit techniques for realizing four different types of AFs, such as the step, identity, rectified-linear unit (ReLU), and the sigmoid, based on stochastic computing. The proposed AF circuits are simpler and consume considerably lesser power than the existing ones. A handwritten digit recognition system employing the AF circuits has been simulated for verifying the effectiveness of the techniques.