Silicon synaptic conductances

We have developed compact analog integrated circuits that simulate two syna ptic excitatory conductances. A four-transistor circuit captures the dynami cs of an excitatory postsynaptic current caused by a real AMPA conductance. A six-transistor circuit simulates the effects of a real voltage-dependent NMDA conductance. The postsynaptic current dynamics are modeled by a curre nt mirror integrator with adjustable gain. The voltage dependence of the si licon NMDA conductance is realized by a differential pair. We show the oper ation of these silicon synaptic conductances and their integration with the silicon neuron (Mahowald and Douglas, 1991).