A p-channel MOS synapse transistor with self-convergent memory writes

We have developed a p-channel floating-gate-MOS synapse transistor for sili con-learning applications, The synapse stores a nonvolatile analog weight b y means of charge on its floating gate, modifies this weight bidirectionall y using electron tunneling and hot-electron injection, and allows simultane ous memory reading and writing. The synapse also learns locally-its weight updates depend only on the applied terminal voltages and on the stored weig ht, We fabricated an array of synapses that computed both the array output, and the weight updates, in parallel. We also demonstrated a self-convergen t write procedure that permitted accurate initialization of the synapse wei ghts. Our pFET synapse is small, and is operated at subthreshold current le vels; it will permit the development of dense, low-power, silicon learning systems.