Keithley Series 2600 User Manual

4 -3
SECTION 4
FET Tests
Source V•
Local sensing•
100mA compliance, autorange measure•
vdsstart • : 0V
vdsstop • : 10V
vdssteps • : 100
1 NPLC Line cycle integration•
Following setup of both units, the outputs are zeroed and
enabled. The first gate-source bias (V
GS
) source value is applied
and the drain-source voltage (V
DS
) sweep is started. At each point
in the V
DS
sweep, the drain current (I
D
) is measured. When the
final V
DS
value is reached, the drain-source voltage is returned
to 0V, the gate-source voltage (V
GS
) is incremented, and the V
DS
sweep begins again.
Upon reaching the final V
DS
value, the outputs are zeroed, dis-
abled, and the data (V
GS
, V
DS
, and I
D
) is printed to the Instrument
Console Window of TSB, where it can be copied and pasted to a
spreadsheet for graphing.
4.3.5 Modifying Program 9
For other V
GS
values, simply modify the vgsstart , vgsstop ,
and vgssteps variables as required.
Similarly, V
DS
can be swept over a different range by changing the
vdsstart, vdsstop, and vdsstep variables to the desired values.
4.4 Transconductance Tests
The forward transconductance (g
fs
) of an FET is usually meas-
ured at a specific frequency (for example, 1kHz). Such a test can
be simulated with DC values by using as small an incremental
change in DC parameters as possible. For example, assume that
we source two gate-source voltages, V
GS1
and V
GS2
, and measure
two resulting drain currents, I
D1
and I
D2
. The forward transcon-
ductance can then be approximated as follows:
∆
ID
g
fs
=
____
∆V
GS
where: g
fs
= forward transconductance (S)
∆
ID
= I
D2
– I
D1
∆V
GS
= V
GS2
– V
GS1
Two common plots involving g
fs
include g
fs
vs. V
GS
and g
fs
vs. I
D
.
The programming examples included in this section demonstrate
how to generate g
fs
vs. V
GS
and g
fs
vs. I
D
plots.
4.4.1 Test Configuration
Figure 4-3 shows the general test configuration for transconduc-
tance tests. SMUB sweeps V
GS
, while SMUA sources V
DS
and also
measures I
D
. g
fs
values are computed from incremental changes in
I
D
and V
DS
. Note that an N-channel FET such as a SD210 is recom-
mended for use with the example programs that follow.
Common-Source Characteristics (SD210)
V
DS
(Volts)
V
GS
= 10V
V
GS
= 7.5V
V
GS
= 5V
V
GS
= 2.5V
V
GS
= 0V
I
DS
(Amps)
1.00E–01
8.00E–02
6.00E–02
4.00E–02
2.00E–02
0.00E+00
0 1 2 3 4 5 6 7 8 9 10
Figure 4-2. Program 9 results: Common-source characteristics

Keithley Series 2600 Specifications

General

Model	Series 2600
Measurement Functions	Voltage, Current, Resistance, Power
Resolution	Up to 6.5 digits
Current Source Range	Up to 10A
Communication Interfaces	GPIB, USB
Applications	Semiconductor testing
Category	Source Measure Unit (SMU)
Channels	Single or Dual Channel (varies by model)