An associative memory circuit based on physical memristors

In this paper, a physical Sr0.97Ba0.03TiO3-x (SBT) memristor with the voltage threshold characteristic was prepared. For characterizing the electrical characteristics of SBT memristor accurately, an adaptive voltage threshold memristor model was proposed. The synaptic plasticity of SBT memristor with different pulse stimulation was analyzed. Moreover, a Pavlov associative memory circuit was designed in the LTSPICE environment, which is composed of neuron circuit and memristive synaptic circuit. The neuron circuit can generate spike signals when the input signals exceed the threshold, and the synaptic weight can be tunable continuously by spike signals. Different from other memristive synaptic circuits, the proposed memristive synaptic circuit is based on physical SBT memristor, and the change of synaptic weight can be truly reflected in the circuit. In Pavlov’s dog experiment, when the presynaptic neuron receives the conditioned stimulus (CS) before the unconditioned stimulus (US), the synaptic weight of SBT memristor is increasing and the associative memory is building. When the presynaptic neuron receives the CS alone, or presynaptic neuron receives the CS after the US, the synaptic weight of SBT memristor is decreasing and the associative memory is losing. This phenomenon is highly similar to the building and losing processes of biological associative memory. These experimental results verify the feasibility and applicability of SBT memristor as electronic synapse in neuromorphic applications, and pave the way towards further development of artificial neural networks.