Artificial Neurons Based on CMOS β-Driven Threshold Elements with Functional Inputs

This paper deals with a CMOS based artificial neuron implemented by threshold elements. We consider the artificial neuron as a threshold element with controlled inputs having weights formed during a learning process. A so-called β-driven threshold element is used for in the scheme of the neuron. Functioning of this element is described in a specific ratio form. The β-driven implementation is based on using summarized conductivities of n-and p-chains of a CMOS gate as the ratio of weighted sums. The threshold element has a wider functional capability in comparison with the traditional functional basis. Moreover, its functional capability can be enriched. We propose a method for increasing the functional capability of the threshold element by introducing socalled functional inputs. Each functional input corresponds to a Boolean sum (or product) of a particular subset of input variables. This sum (or product) serves as a single input of the threshold element. It is shown that introducing functional inputs enables expansion of the functional capability of β-driven elements up to the capability to implement an arbitrary monotonic function. The CMOS based implementation of the β-driven threshold element with newly proposed functional inputs is presented. Methods of the current stabilization of functional inputs are proposed. In the proposed implementation of the artificial neuron, each input weight is determined by the current value via a suitable current stabilizer. This value can be effectively controlled by the value of the voltage at the gate of one of the current stabilizer’s transistors. The paper presents examples of the SPICE simulation of behavior of the proposed artificial neuron in the modes of learning and maintaining the input weights values. 1 The project is financed by the Ministry of Industry and Trade of Israel, Magneton Agency (file N 27995). Key-Words: Artificial neuron, threshold element, learnable circuit, CMOS circuits, SPICE-simulation.