This is an improved implementation of Chua's diode, based on 2
imporved NIC
models with opAmps.
Note: This is a demonstration how to realize a piecewise linear
characteristic with opAmps / NICs.
If voltage v is prescribed, the current i can be unambiguously
determined.
If current i is prescribed, in the range between the zero crossings
the voltage v has 2 or 3 possible solutions.