NMOS based circuits to emulate diodes and Zener diodes are proposed, following the tendency to develop fully CMOS compatible solutions towards over-voltage protection and rectifier circuits, which are highly desirable to implement low cost smart power circuits and Microsystems for a wide range of applications. This work will present extensive characterisation, through experiments, on prototypes fabricated using three different standard, low cost, CMOS processes. Comparative analysis of the results supports prospects of implementing the basic blocks required by Power Integrated Circuits (PICs) and by Intelligent Power Devices, resorting only to NMOS switching cells. 658 0-7803-7116-X/01/$10.00 (C) 2001 IEEE