Fig. 3: OAN operation and spiking.
From: Unravelling the operation of organic artificial neurons for neuromorphic bioelectronics
a OAN circuit highlighting the current partition when \({V}_{{{{{{\rm{spike}}}}}}}\) increases, and the capacitor is charged. VIN is the load voltage generator, RL represents the load resistor, CL represents the load capacitance. \({I}_{{{{{{\rm{C}}}}}}}\) represents the current of the capacitor CL, while \({I}_{{{{{{\rm{B}}}}}}}\) is the current flowing through RL. b Voltage oscillations (\({V}_{{{{{{\rm{spike}}}}}}}\)) as a function of time. c OAN circuit highlighting the current partition when \({V}_{{{{{{\rm{spike}}}}}}}\) decreases, and the capacitor is discharged. d OEND (blue full line) and load-line (dashed line) characteristics. When the load-line characteristic crosses the OEND characteristic in the negative differential resistance region (e.g., point \({{{{{\bf{U}}}}}}\)), its response bifurcates, producing voltage and current oscillations. The OEND negative differential resistance is highlighted by dot-dashed purple line. The spiking region is defined by the upper and lower points \({{{{{{\bf{U}}}}}}}_{{{{{{\rm{ON}}}}}}}=({V}_{{{{{{\rm{ON}}}}}}},{I}_{{{{{{\rm{ON}}}}}}})\) and \({{{{{{\bf{U}}}}}}}_{{{{{{\rm{OFF}}}}}}}=({V}_{{{{{{\rm{OFF}}}}}}},{I}_{{{{{{\rm{OFF}}}}}}})\), respectively. \({{{{{{\bf{S}}}}}}}_{1}\) and \({{{{{{\bf{S}}}}}}}_{2}\) are two points where the OEND characteristic shows a positive resistance. e Spiking frequency \({f}_{{{{{{\rm{spike}}}}}}}\) as a function of load capacitor (CL). Symbols are the measurements, full line is calculated with the numerical simulations and dashed line is calculated with the analytical model. f Spiking current as a function of time measured (symbols) and calculated with non-linear transient simulations (full line) in the case \({C}_{{{{{{\rm{L}}}}}}}\) = 1 µF, g \({C}_{{{{{{\rm{L}}}}}}}\) = 5 µF, and h \({C}_{{{{{{\rm{L}}}}}}}\) = 10 µF.
