Environmental Engineering Reference
In-Depth Information
and substituting this value in (1.25) leads to
The current is linearly related to and has a quadratic dependence
on Under this condition the device is said to operate in triode or linear
region. Note also that (1.30) is reduced to (1.26) for small values of
1.3.3
Saturation or Active Region
A further increase of can lead to the condition of a gate-drain voltage
equal to In this case the charge density close to the drain,
becomes zero and current
reaches its maximum value. This condition is
shown in Fig. 1.8.
At a first approximation, the current does not change over this point with
since the charge concentration in the channel remains constant and the
electron carriers are velocity saturated. Under this condition the transistor is
said to work in saturation or linear region.
Denoting as the drain source voltage when the charge density
becomes zero, we can find an equivalent relationship that expresses the
pinch-off condition by substituting
into
Specifically, we get
where
