Bias Circuit

The input circuit loop equation (Fig. 3.4) is
Equation 3.16
Including the body effect, VGS is now [from (3.12)]
Equation 3.17
where, for this special case, VDS = VGS (VD = 0, VS = 0).
A solution is obtainable through combing (3.14), (3.16), and (3.17) for ID and VGS. These
equations contain every parameter from this discussion of MOSFET SPICE parameters along
with RS. In a project Mathcad file, Project04.mcd, a solution is obtained to provide a
comparison with the measured VGS versus ID for the circuit. The Mathcad iteration formulation
is, from (3.16),
Equation 3.18
and, from (3.15) and (3.17),
Equation 3.19
ID and VGS are found for the range of VSS corresponding to that used in the measurement,
which is 2.5 < |VSS| < 10 V.