Keithley S530

Section 3: Test subroutine library reference S530 Parametric Test System Test Subroutine Library User's Manual
3-78 S530-907-01 Rev. A / September 2015
vtext3
This subroutine estimates the extrapolated gate-source threshold voltage of a metal-oxide field-effect transistor
(MOSFET) using a condensed version of the vtext and vtext2 subroutine method.
Usage
void vtext3(int d, int g, int s, int sub, double vg1, double vg2, double vds,
double vbs, int npts, double *slope, double *vt, int *flag);
d
Input
The drain pin of the device
g
Input
The gate pin of the device
s
Input
The source pin of the device
sub
Input
The substrate pin of the device
vg1
Input
Start of the gate-source voltage (V
GS
) search, in volts
vg2
Input
End of the V
GS
search, in volts
vds
Input
Drain voltage, in volts
vbs
Input
Substrate bias, in volts
npts
Input
The number of points in the sweep
slope
Output
The calculated inductance
vt
Output
Threshold voltage
flag
Output
Return status:
0 = Normal operation
1 = Bad data collected
2 = Calculated linear least-squares (LLSQ) slope = 0.0, bad data
Returns
Output
The extrapolated gate-source voltage
Details
This subroutine is the most condensed form of the basic maximum slope techniques to find threshold
voltage (V
T
).
This subroutine does the following to estimate V
T
:
1. Sweeps a drain-source current (I
DS
), gate-source voltage (V
GS
) array (using the idvsvg
subroutine).
2. Differentiates the data set using dy/dx notation (also known as Leibniz's notation).
3. Finds the maximum slope.
4. Finds the index of the maximum slope in the slope array.
5. Returns the gate-source voltage (V
GS
) intercept and slope.
V/I polarities
N-channel +V
DS
, +V
G
, -V
BS
P-channel -V
DS
, -V
G
, -V
BS