Complex sentence: Another variant is to use diodes or resistors, but neither diodes (e.g. Metal insulator metal diodes), nor non-linear voltage dependent resistors (i.e. varistors) are currently used.
Split into simpler sentences: Another variant is to use diodes or resistors. But neither diodes (e.g. Metal insulator metall diodes), nor non-linear voltage dependent resistors (i.e. varistors) are currently used.