The ultimate thermal switching energy limit ln(2)kT of an electronic gate and
the ultimate quantum switching energy h of an optical gate (i.e., the photon
energy at a wavelength of 1.55 mm) are included in Figure 17.9 for comparison
with CMOS gate switching energies. The actual swit ching energy for reliable
operation will always be larger than these lower theoretical limits, and we have
therefore also included the more practical lower limits of 100 ln(2)kT and 100 h,
respectively. It is interesting to note that around the in the year 2011, the switching
energy of a CMOS gate will be equal to this 100 h lower limit on switching
energy for an optical gate.
The energy dissipation in electronic circuits is influenced not only by the gate
switching