a circuit , method and system for generating a non - linear transfer characteristic , including a plurality of current mirror circuits in parallel , each current mirror circuit having an offset current applied to an output terminal of an output - side transistor of the current mirror circuit for controlling an output current thereof , wherein the offset current of each current mirror circuit is set to a respective predetermined level , and the transfer characteristic is generated by summing the respective output currents of the current mirror circuits in a piece - wise manner .