In order to emulate neural behavior a device was needed that possessed an excitation characteristic similar to a biological neuron. LEDs were used for this purpose. Figure 1 shows the excitation function of a biological neuron and the excitation function used for this project which is the response of the LED to voltage applied across its terminals. Thresholding The connection weights were implemented by varying the photo transistor circuit parameters. The phototransistors were analogous to dentrites in biological neurons.
Dendrites serve as input devices to the neuron.
A single neuron may have a large number of dendrites. Each input neuron for this circuit received input from four photodetectors, corresponding to four dentrites. This network consists of four input neurons and a single output neuron. Figure 2 shows a block diagram of the network. The output neuron receives input from each of its four photo detectors, which are each directly across from one of the four input neuron LEDs.