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
D
S
(
A
m
p
s)
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
Содержание Series 2600
Страница 5: ......
Страница 7: ......
Страница 17: ...2 8 Section 2 Two terminal Device Tests...
Страница 39: ...4 10 Section 4 FET Tests...
Страница 53: ...6 4 Section 6 High Power Tests...
Страница 130: ...A 77 Appendix A Scripts BJT_Comm_Emit_Vsb...
Страница 136: ...Click below to find more Mipaper at www lcis com tw Mipaper at www lcis com tw...