Patent US 5,535,148

A method and apparatus for approximating a sigmoidal response using digital circuitry for neural network computations. The digital circuitry in processing element (16) produces the neuron output signal (110) by performing a squashing operation which determines an approximation of a sigmoid function. In one form, the present invention uses digital circuitry (16) in data processor (10) to approximate a sigmoid function of a neuron (100) using a plurality of parabolas. In an alternate embodiment, the sigmoid function of neuron (100) is approximated using a quasi-log.sub.2 function.