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4 .
Turn on the computer and start Test Script Builder (TSB) . Once
the program has started, open a session by connecting to the
instrument . For details on how to use TSB, see the Series 2600
Reference Manual .
5 .
You can simply copy and paste the code from Appendix A in
this guide into the TSB script editing window
manually enter the code from the appendix, or import the TSP
file 'DC_Gain_Search.tsp' after downloading it to your PC .
If your computer is currently connected to the Internet, you
can click on this link to begin downloading:
keithley.com/data?asset=50925
6 .
Install an NPN transistor such as a 2N5089 in the appropriate
transistor socket of the test fixture .
7 .
Now, we must send the code to the instrument . The simplest
method is to right-click in the open script window of TSB,
and select 'Run as TSP file' . This will compile the code and
place it in the volatile run-time memory of the instrument .
To store the program in non-volatile memory, see the "TSP
Programming Fundamentals" section of the Series 2600 Refer-
ence Manual .
8 .
Once the code has been placed in the instrument run-time
memory, we can run it at any time simply by calling the func-
tion 'DC_Gain_Search()' . This can be done by typing the text
'DC _ Gain _ Search()' after the active prompt in the
Instrument Console line of TSB .
9 .
In the program '
DC_Gain_Search.tsp', the function DC _
Gain _ Search(vcesource,
targetic) is created .
•
represents the voltage value on the
vcesource
collector-emitter of the transistor
•
represents the base current low limit for the
lowib
search algorithm
•
represents the base current high limit for the
highib
search algorithm
•
represents the target collector current for the
targetic
search algorithm
10 .
If these values are left blank, the function will use the default
values given to the variables, but you can specify each vari-
able value by simply sending a number that is in-range in
the function call . As an example, if you wanted the collector-
emitter voltage (V
) to be 2 . 5 V, the base current low value
CE
at 10nA, the base current high value at 100nA, and the
target collector current to be 10µA, you would send DC _
Gain _ Search(2.5,10E-9, 100E-9, 10E–6) to the
instrument .
11 .
The sources will be enabled, and the collector current of
the device will be measured . The program will perform an
(Program
6A),
http://www.
lowib,
highib,
iterative search to determine the closest match to the target
I
(within ±5%) . The DC current gain of the device at specific
C
I
and I
values will then be displayed on the computer CRT .
B
C
If the search is unsuccessful, the program will print "Itera-
tion Level Reached" . This is an error indicating that the search
reached its limit . Recheck the connections, DUT, and variable
values to make sure they are appropriate for the device .
12 .
Once the sweep has been completed, the data (I
will be presented in the Instrument Console window of TSB .
3.5.5 Typical Program 6A Results
A typical current gain for a 2N5089 would be about 500 . Note,
however, that the current gain of the device could be as low as
300 or as high as 800 .
3.5.6 Program 6A Description
Initially, the iteration variables are defined and the instrument is
returned to default conditions . SMUB, which sources I
as follows:
•
Source I
•
IV compliance, 1 . 1 V range
•
Local sense
SMUA, which sources V
CE
follows:
•
Source V
•
Local sense
•
100mA compliance, autorange measure
Once the SMU channels have been configured, the sources values
are programmed to 0 and the outputs are enabled . The base cur-
rent (I
) is sourced and the program enters into the binary search
B
algorithm for the target I
by varying the V
C
I
, comparing it to the target I
C
essary . The iteration counter is incremented each cycle through
the algorithm . If the number of iterations has been exceeded, a
message to that effect is displayed, and the program halts .
Assuming that the number of iterations has not been exceeded,
the DC current gain is calculated and displayed in the Instrument
Console window of the TSB .
3.5.7 Modifying Program 6A
For demonstration purposes, the I
to ±5% . You can, of course, change this tolerance as required .
Similarly, the iteration limit is set to 20 . Again, this value can be
adjusted for greater or fewer iterations as necessary . Note that it
SeCTIon 3
Bipolar Transistor Tests
, I
B
C
, is set up
B
and measures I
, is configured as
C
value, measuring the
CE
, and adjusting the V
value, if nec-
C
CE
target match tolerance is set
C
, and ß)
3-7
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