The semiconductor capacitance in the gate may be defined by
where 
is the total charge in the gate per unit
area. Here, as throughout the whole appendix, we omit the interface and bulk
traps in consideration. In order to find 
, we
derived A.11 with respect to 
. The expression for 
becomes
which is valid if 
. For 
the flat-band condition
occurs in the gate and 
holds too, since the doping is assumed to be
uniform. Applying 
on the left and the right-hand-side
of A.18, after transformations, it leads the flat-band capacitance
In deriving, we benefitted from A.12. In e.g. 
-type of
silicon, the second summand due to holes in the expression for 
is
negligible and reduces to formula 2.1. For MB
statistics we simply approximate 
.
Adopting MB statistics for both carriers, relationship A.18 simplifies to
