Synthesis of log-domain integrators for silicon synapses with global parametric control

We present a series of circuits for implementing silicon synapses with biologically plausible temporal dynamics and independent global control over gain and time-constant. These types of circuits are useful for implementing synaptic dynamics in neuromorphic networks of spiking neurons, and adaptive or homeostatic mechanisms for controlling the synaptic weights. We demonstrate very compact circuit solutions, with as few as six transistors, that can be used as synaptic elements which behave like linear-integrators. The integrators are designed with translinear loops and provide an intuitive and flexible synthesis methodology.