CMOS full-wave operational transconductance rectifier with improved DC transfer characteristic

The proposed full-wave rectifier is based on a source-coupled pair associated with a new current-mode circuit that computes the absolute value of the difference of two currents. The DC transfer characteristic is well controlled through technology parameters because device mismatches and channel length modulation give rise to distinct imperfections. In addition, it reaches zero output current at the origin in every case. These properties make the circuit suitable for dense implementation of Manhattan distance computation in analogue VLSI neural networks.