  The boundary sheath of a low temperature plasma comprises typically only a
small fraction of its volume but is responsible for many aspects of the
macroscopic behavior. A thorough understanding of the sheath dynamics is
therefore of theoretical and practical importance. This work focusses on the
so-called "algebraic" approach which strives to describe the electrical
behavior of RF modulated boundary sheaths in closed analytical form, i.e.,
without the need to solve differential equations. A mathematically simple,
analytical expression for the charge-voltage relation of a sheath is presented
which holds for all excitation wave forms and amplitudes and covers all regimes
from the collision-less motion at low gas pressure to the collision dominated
motion at gas high pressure. A comparison with the results of self-consistent
particle-in-cell simulations is also presented.
