Correlation learning rule in floating-gate pFET synapses

We study the weight dynamics of the floating-gate pFET synapse and the effe cts of the pFET's gate and drain voltages on these dynamics, We show that w e can derive a weight update rule such that the equilibrium weight value is proportional to the correlation between the gate and drain voltages. In pa rticular, we want a rule of the form tau (1) DeltaW (over dot) = -DeltaW etaE[xy],where x is a voltage signal on the gate terminal and y is a voltag e signal on the drain terminal, We obtain this rule by making a linear appr oximation to the weight dynamics around a given equilibrium point. We devel op this approximation by considering the basic functional form of the syste m dynamics and then examining the effects of the gate and drain voltages on the specifies of this form.