Figure 3.

Circuits of our low-power analog silicon neuron. (A–C) Elemental circuits and (D) block diagram. The voltage clamp amplifier placed at the top in the block diagram is used to measure the nullclines experimentally. It is a transconductance amplifier that provides a negative feedback loop to the active terminal of C_v. When SW_v is closed, it locks v near V_c, which is an input voltage of the amplifier. If SW_q and SW_n are open, its output current I_v compensates the current generated by the f_m, g_v, and I_a circuits. By scanning V_c in an appropriate range and measuring I_v, I_n, and I_q, the v-, n-, and q-nullclines are measured, respectively. The copied outputs of those currents are available for this purpose. This circuit is exploited to find the appropriate parameter voltages that replicate the dynamical structure in the ideal model, which are altered from their ideal values by fabrication mismatch and the transistors' second effects. Reprinted with modification from Kohno et al. (2014b).