AN2657

Model description and parameter extraction

7/18

L is the physical channel length of the MOS, while L0 influences the output conductance

which depends on KE and EPS. DEL and DELVG affect the VDSAT and are extracted from

the output characteristics in the saturation region. As mentioned previously, all the equations

have been implemented in verilog language.

JFET resistance

The quasi-saturation region is modeled by a nonlinear JFET resistor. The mathematical

empirical equation is defined in Equation 12, where pres depends on the current and on the

Equation 12

Figure 2.

Useful to delete any convergence problem, Figure 2 shows the resistor law for the variation

of Vds (using the right hand function approach) (Equation 13). A similar graph and function

can be obtained by varying Vgs [3].

Equation 13

The function g(pres) was created to bind the Rj to the current Id. This is accomplished by

is linked to the dissipated power on Rj through RPWR.

Equation 14

are temperature coefficients in the linear region.

R

j

fVds Vgs

,

() gpres

() hT

()

⋅

⋅

=

R

()

RI0

SR

FSI

Log

Vds

VDI

–

FSI

----------------------------

+

⎝⎠

⎜⎟

⎛⎞

FSF

Log

Vds

VDF

–

FSF

------------------------------

+

⎝⎠

⎜⎟

⎛⎞

⋅

–

⋅

⋅

+

=

gpres

() 1

PCR1

PCR2

pres

⋅

+

() pres

⋅

+

=