Selective similarity function for VLSI analog signal processing

The similarity calculation of two input voltages can be performed in the analog domain by means of a very compact current switch combined with a differential pair stage. Local feedforward of the current switch allows the circuit to work without the need of any external control ensuring at the same time very high selectivity. The current switch is analyzed by means of its large-signal model, since the first-order small-signal model is not enough to obtain insight into its behavior. The obtained peak cell circuit is applied to bioinspired gray-level image segmentation focal-plane processor. Other direct applications of the current switch are full-wave differential rectifiers and two-input maximum/minimum circuits.