LabVIEW Data Curve Fitting for MOSFET Parameter Extraction – Level 3 Spice

Sample curve fit here is for a measured transfer function (NMOS, grounded source), with stepping Vg and maintaining Vds=3 V. UO fits the sum of the points of the two curves and VTO, the slope of the difference.  The minimum current is selected to be consistent with strong inversion.

Block Diagram of the VI

Sum-Slope Computer – Scatter is from DAQ measurement.

UO Root Finder

Root Finder Loop

VTO Function

Note that VTO is initial value sensitive. Solution is VTO = 1.52 V for f = 0.

Iterate – Iteration variable vx in this case is UO.

Spice Level 3 Simulator

ETA Parameter is not included, as is effect from XJ not zero. UCRIT (VMAX)  dependence is on Vdsat and effective mobility due to velocity saturation (denominator in iD expression).  THETA effect is that from computing Vb from VC.

Slope For For KAPPA – Saturation

OC Fit For UCRIT – From velocity saturation effect in pre-saturation.

Initialization Computations

Some Parameters – NMOS – NXP HEF4007 CMOS