Accurate design of a MOS-based resistive network for time-controlled diffusion filtering

This paper analyses a MOS-based resistive network suitable for massively parallel image processing. The inclusion of MOS transistors biased in the ohmic region instead of true resistors permits certain control over the underlying spatial filtering while reducing the required area for VLSI implementation. However, it also leads to nonlinearities and thereby to errors with respect to an ideal resistive grid. By studying an elementary network composed of only two nodes we determine the guidelines to be followed in order to minimize the error according to the selected signal range. These guidelines are then extrapolated to larger networks demonstrating that pretty accurate networks can be achieved even for relatively wide signal ranges. Simulations are employed to validate the extrapolated results. The numerical examples will also allow to visualize how the insertion of MOS transistors affects the spatial filtering carried out by the grid.