A Compact Integrate-and-Fire Neuron Circuit Embedding Operational Transconductance Amplifier for Fidelity Enhancement

In this study, a compact CMOS integrate-and-fire (I&F) neuron circuit embedding an operational transconductance amplifier (OTA) has been designed for enhancing the fidelity in output generation. The OTA block in the neuron circuit allows for maintaining stability in I&F functions even under high-frequency operation conditions. The designed neuron circuit consists of OTA circuit, membrane capacitor, inverter, and reset MOSFET, from which the area occupancy is approximated to be 22×43 μm2. Featuring the simple and compact structure, the proposed neuron circuit shows the capability to control the firing frequency by adjusting the amplitude and temporal width of the synaptic pulse, resulting in high fidelity in I&F function. Series of circuit simulations have been performed to validate the systematic operations of the neuron circuit by HSPICE presuming the 0.35-μm Si CMOS technology. Moreover, temperature dependence was also investigated so that the robustness and stability of the neuron circuit at elevated operation temperatures were verified. The results provide a practical way of designing a compact and reliable neuron circuit working with the synaptic devices having deviations in operation characteristics in the hardware-oriented spiking neural network (SNN).