Simple analog edge detection circuit based on vertebrate retina

Novel analog edge detection circuits were proposed and fabricated based on the vertebrate retina. The proposed unit circuit is constructed with one photodiode and about eight n-channel metal oxide semiconductor (MOS) transistors. The results with the simulation program with integrated circuit emphasis (SPICE) showed that the one- and two-dimensional array of proposed circuits can detect edge positions with a dynamic range of about 5 decades. The test circuit was fabricated on the breadboard using discrete MOS transistors. The measured results of the test circuit showed that the proposed circuit can detect edge positions. Under the condition that the photodiode used as the input part of the proposed unit circuit is 4,275 μm², the fill factor of the novel circuit is expected to be about 51.7%. The advanced integrated circuit for edge detection which is characterized by a high fill factor, wide dynamic range and low power consumption can be realized by applying the proposed circuit.