Low power current-mode binary-tree asynchronous Min/Max circuit

A novel, current-mode, binary-tree, asynchronous Min/Max circuit for application in nonlinear filters as well as in analog artificial neural networks is proposed. The relatively high precision above 99% can be achieved by eliminating the copying of the input signals from one layer to the other in the tree. In the proposed solution, the input signals are always directly copied to particular layers using separate signal paths. This makes the precision almost independent on the number of the layers i.e. the number of the inputs. The circuit is a flexible solution. The power dissipation, as well as data rate can be scaled up and down in a wide range. For an average value of the input currents of 20 μA and data rate of 11 MHz the circuit dissipates 505 μW, while for the signals of 200 nA and data rate of 500 kHz the power dissipation is reduced to 1 μW. The prototype circuit with four inputs, realized in the CMOS 0.18 μm technology, occupies the area of 1800 μm2.