Four logic states using two resonant tunnelling diodes

Using a series connection of two specially designed resonant tunnelling diodes, the authors observed three negative differential resistance regions, resulting in four possible logic states. This behaviour can be expanded, at least in theory, to n tunnelling diodes, resulting in 2ⁿ-1 times switching and 2ⁿ logic states. These new devices can be used for analogue/digital conversion and multivalued logic or as multistate memory cells using only a minimum in device area.