Keithley SourceMeter 2470, User Manual, Page: 73 / 86

Model 2470 High Voltage SourceMeter Instrument User's Manual Section 6: Measure I-V characteristics of FETs
2470-900-01 Rev. A /
May
2019 6-15
Set up a subthreshold current measurement using TSP
commands
The following TSP code uses the trigger model to find the subthreshold swing, S, of a FET using two
2470s communicating with each other using TSP-Link. The SMU at Node 1 is connected to the gate
and steps voltage from 0 V to 5 V. The SMU at Node 2 is connected to the drain and applies a bias
voltage while measuring current.
After the measurement is complete, a simple numerical exponential fit is found and the subthreshold
swing, S, is taken as the inverse of the exponential slope. The result and measurement data is
displayed in the Instrument Console of Test Script Builder. From the Instrument Console, you can
copy the data into a spreadsheet for graphing.
Send the following commands for this example application:
--######################## Settings and TSP-Link setup ################
local gateVstart = 0
local gateVstop = 5
local gateStepSize = 0.1
local gateIlimit = 0.1
local drainV = 10
local drainIlimit = 0.1
-- Fit settings - The slope is calculated between these gateV points.
-- fitHighV should be less than or equal to the threshold voltage.
local fitLowV = 2
local fitHighV = 3.5
-- Reset the instruments and the TSP-Link connection and clear the buffers.
tsplink.initialize()
reset()
-- If the tsplink state is not online, print an error message and quit.
state = tsplink.state
if state ~= "online" then
print("Error:\n-Check that all SMUs have a different node number")
print("-Check that all SMUs are connected correctly\n")
return
end
-- Set up TSP-Link node shortcuts.
local gate = node[1]
local drain = node[2]
--######################## 2470 SMU #1 (gate) setup ################
-- Set up the source function.
gate.smu.source.configlist.create("stepVals")
gate.smu.source.func = gate.smu.FUNC_DC_VOLTAGE
gate.smu.source.autorange = gate.smu.ON
gate.smu.source.ilimit.level = gateIlimit
-- Set up the measure function.
gate.smu.measure.func = gate.smu.FUNC_DC_CURRENT
gate.smu.measure.autorange = gate.smu.ON
gate.smu.measure.terminals = gate.smu.TERMINALS_REAR