The prime concern for any implant intended for chronic
use is safety. For example, the stimulator output stage which
directly connects to the electrodes should not fail as this may
result in tissue damage due to electrolysis. Experiments have
shown that a 2-3 μA of prolonged DC current leads to
permanent damage of the auditory nerve or central nervous
system [1]. However, any semiconductor circuit can fail [2]
and therefore, most implanted stimulators feature some form
of safety protection.