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