Keithley S530 - Vp1

S530 Parametric Test System Test Subroutine Library User's Manual Section 3: Test subroutine library reference
S530-907-01 Rev. A / September 2015 3-69
vp1
This subroutine estimates the voltage at which the current flow between the source and drain is blocked
("pinched-off") for a metal-semiconductor field-effect transistor (MESFET) at a specified "pinch-off" current and
drain-source voltage (V
DS
).
Usage
void vp1(int d, int g, int s, int sub, double ids, double vdlim, double vg1, double
vg2, double iglim, double *iflag, double *vp)
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
ids
Input
The forced drain current (I
P
), in amperes
vdlim
Input
The drain voltage target, in volts
vg1
Input
Start of the gate-source voltage (V
GS
) search, in volts
vg2
Input
End of the V
GS
search, in volts
iglim
Input
Gate current limit, in amperes
iflag
Output
Return status flag:
0 = Normal completion
1 = Pinch-off voltage (V
P
) is 0.0
2 = Device triggered on starting voltage
3 = Device triggered on ending voltage
Returns
Output
Measured V
P
Details
This subroutine is a variant of the vp subroutine. The trigger is set to the specified V
DS
and pinch-off
current (I
P
) is forced on the drain. The gate voltage is then searched until the V
DS
value is reached. At
0 V gate-source voltage (V
GS
), the drain voltage is below the specified V
DS
. As V
GS
is increased, V
DS
increases as the device approaches the voltage at which the current flow between the source and
drain is blocked.
If a positive substrate pin is specified, the substrate is grounded. If a positive substrate pin is not
specified, the substrate is left floating.
A delay is incorporated into the vp1 subroutine; this delay is the calculated time required for stable
forcing of drain-source current (I
DS
) with the V
DS
voltage limit.
V/I polarities
vg1, vg2 - Ensures that polarity forward biases the gate-source diode. Starting voltage, vg1, must
allow the drain SMU to supply pinch-off current without exceeding the limit.
Source-measure units (SMUs)
 SMU1: Forces drain-source current (ids), programmable voltage limit, trigger set to V
DS
 SMU2: Searches V
GS
, programmable current limit