where C is the FET gate switch capacitance, k is Boltzmann's
constant, and T is the absolute temperature of the CCD chip measured in
K. Using the relationships
, the
output RMS value of the KTC noise expressed in terms of the number of
photoelectrons (
) is
given by:
where e- is the electron charge. For C = 0.5 pF and
T = 233 K this gives
. This
value is a "one time" noise per pixel that occurs during signal readout and is
thus independent of the integration time (see Sections 6.1 and 7.7). Proper
electronic design that makes use, for example, of correlated double sampling and
dual-slope integration can almost completely eliminate KTC noise .