Keithley S530 User Manual page 46

Section 3: Test subroutine library reference
gm
This subroutine estimates transconductance of a metal-semiconductor field-effect transistor (MESFET) at a
specified drain voltage (V
Usage
double gm(int d, int g, int s, int sub, double vds, double idlim, double vgs,
double vgstep, double iglim, int *iflag)
d
g
s
sub
vds
idlim
vgs
vgstep
iglim
iflag
Returns
Details
This subroutine estimates the transconductance of a MESFET at a specified V
voltage is forced, and then five V
specified V
GS
squares (LLSQ) line is fit through the data and the transconductance is estimated from the slope of
the line.
V/I polarities
N-channel +V
P channel -V
Source-measure units (SMUs)

SMU1: Forces vds, programmable current limit, measures I

SMU2: Sweeps vgs, programmable current limit
3-34
) and gate voltage (V
DS GS
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
Input Drain voltage, in volts
Input Drain current limit, in amperes
Input Gate voltage, in volts
Input
V step size, in volts
GS
Input Gate current limit, in amperes
Output Return status flag:

0 = Normal completion

1 = Not enough valid data for LLSQ

2 = Current limit reached (98 % of iglim or idlim)
Output Estimated MESFET transconductance
to I
GS
step size is defined by the input parameter vgstep). Then a linear least
(the V
GS
, +V
DS GS
,- V
DS GS
S530 Parametric Test System Test Subroutine Library User's Manual
).
(drain-source current) data points are taken around the
DS
and V
DS GS
DS
S530-907-01 Rev. A / September 2015
. A drain