Neural network circuit and learning method for neural network circuit

A neural network circuit comprising:

• a plurality of neural network circuit elements;
• an error calculating circuit;
• at least one input signal terminal;
• and
• at least one output signal terminal,
• wherein at least one output signal output from the at least one output signal terminal is obtained from an input signal input to the at least one input signal terminal,
• wherein the error calculating circuit receives the at least one output signal and teaching signals equal in number to a number of the at least one output signal terminal and generates an error voltage signal representing a voltage signal having an amplitude in accordance with a time difference between an output signal and a teaching signal corresponding to one of the least one output signal,
• wherein each of the neural network circuit elements includes at least one synapse circuit and a neuron circuit,
• wherein the synapse circuit includes a variable resistive element having a resistance value that varies when a pulse voltage is applied,
• wherein the neuron circuit includes a waveform generating circuit, and the waveform generating circuit generates a weight change pulse voltage signal having a predetermined first waveform that rises from a reference value to a predetermined peak value and then falls again to the reference value as time passes and a switching pulse voltage signal having a predetermined second waveform that determines a predetermined duration,
• wherein the weight change pulse voltage signal is input to the synapse circuit of the neural network circuit element including the neuron circuit that outputs the weight change pulse voltage signal,
• wherein the switching pulse voltage signal is input to the synapse circuit of the neural network circuit element other than the neural network circuit element including the neuron circuit that outputs the switching pulse voltage signal,
• wherein the neural network circuit element changes an amplitude of the weight change pulse voltage signal on the basis of the error voltage signal generated by the error calculating circuit, and
• wherein for the predetermined duration of the switching pulse voltage signal input from the neural network circuit element other than the neural network circuit element including the synapse circuit, the synapse circuit changes the resistance value of the variable resistive element of the synapse circuit using a voltage in accordance with a time difference between the switching pulse voltage signal and the weight change pulse voltage signal generated by the neuron circuit of the neural network circuit element including the synapse circuit.