Vtext - Keithley S530 User Manual

S530 Parametric Test System Test Subroutine Library User's Manual

vtext

This subroutine estimates the extrapolated gate-source threshold voltage of a metal-oxide field-effect transistor
(MOSFET).
Usage
double vtext(int d, int g, int s, int sub, char type, double vlow, double vhigh,
double vds, double vbs, double ithr, double vstep, int nmax, double *slope, int
*kflag)
d
g
s
sub
type
vlow
vhigh
vds
vbs
ithr
vstep
nmax
slope
kflag
Returns
Details
This subroutine estimates the extrapolated threshold voltage of a MOSFET using the maximum slope
method. Maximum slope refers to the common technique of numerically differentiating the I
V curve. Slope refers to the FET transconductance (g
GS
This subroutine uses a two-step method of finding V
a drain current (I
devices this value is 1 μA). If the measured I
sliding five-point linear least-squares (LLSQ) analysis of the I
S530-907-01 Rev. A / September 2015
Input The drain pin of the device
Input The gate pin of the device
Input The source pin of the device
Input The substrate pin of the device
Type of transistor: "N" or "P"
Input
Input
The start of the gate-source voltage (V
Input
The end of the V
Input The forced drain voltage, in volts
Input Substrate bias, in volts
Input
Drain-source trigger current (I
Input
V step size, in volts
GS
Input The maximum number of steps
Output The calculated slope
Output Return status flag:

0 = Normal operation

1 = The ithr parameter is too high; indicates that the vlow
parameter is above the voltage threshold (V
constantly decreasing

2 = Did not find peak slope; indicates that the vhigh parameter
was below V

3 = Binary search on V
vhigh parameters were below V

4 = The type parameter was not specified as "N" or "P"

5 = V
Output Gate-source voltage threshold, in volts.
) that is within 0.25 of the estimated threshold current (for most enhancement
DS
Section 3: Test subroutine library reference
binary search, in volts
GS
), in amperes
DS
(maximum slope was the last value)
T
failed; may indicate that the vlow and
GS
step size is 0.0
GS
).
m
. First, a binary search is done on the V
T
value is within tolerance, the routine continues with a
DS
-V
DS GS
) binary search, in volts
GS
) and the slope is
T
and the device never turned on
T
DS
curve.
versus
to find
GS
3-73