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 .