if the voltage drop across the blocking capacitor is 1V, a 1μF
capacitor is required. Clearly, such large capacitors are
impossible to integrate onto a silicon chip with standard
silicon technologies. Therefore, these capacitors are realized
as surface mount devices. The volume of capacitors is
currently about 5mm3/μF [9], [10] and therefore, with 10
outputs, the volume occupied by 10 1μF capacitors is about
50mm3. Even in stimulators with around 10 outputs, this
volume is likely to be similar to that occupied by all the other
components and in devices with hundreds or thousands of
outputs, the physical size of an implantable stimulator package
would be dominated by their volume. This is a major problem
for the miniaturization of FES implanted devices.