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Schematic diagram of the circuit that converts a dc voltage into a spike train output using a SCR and a parallel ( and ) load. The lead labeled is the gate, which is usually used for external triggering of SCR.
Measured sequence of pulses as a function of time for a dc bias across the circuit. The pulse height is measured across the circuit and is approximately equal to the switching voltage of the SCR.
Measured current-voltage characteristics of the SCR showing the on and off states. The switching voltage of the SCR is about . The inset shows the schematic band diagram and charge accumulation in the SCR just below switching voltage (in the off state). The dashed line shows the load line of the circuit.
Measured pulse rate as a function of dc bias across the circuit. The saturation of the pulse rate at high bias is due to the time constant of the output circuit. For the parameters used saturation occurs around . The inset shows pulse rate prior to saturation plotted in log scale to illustrate the exponential dependence with bias.
Measured pulse sequences under light illumination at three different intensities. The dc bias across the circuit was kept at about and no pulses were observed in the absence of light. The light power levels incident on the photodiode are given next to each plot. Note that the responses at different light powers were shifted vertically for clarity.
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