Keithley Series 2600 Application Manual Download

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3-2

SeCTIon 3

Bipolar Transistor Tests

plotting styles include graphing I

vs . V

for each value of I

. The

result is a family of curves that shows how I

varies with V

specific I

values .

3.3.1 Test Configuration

Figure 3-1

shows the test configuration for the common-emitter

characteristic tests . Many of the transistor tests performed require
two Source-Measure Units (SMUs) . The Series 2600 System
SourceMeter instruments have dual-channel members such as the
Model 2602, 2612, and 2636 . This offers a convenient transistor
test system all in one box . The tests can be run using two single-
channel instruments, but the code will have to be modified to
do so .

In this test, SMUB sweeps I

across the desired range, and SMUA

sweeps V

and measures I

. Note that an NPN transistor is shown

as part of the test configuration . A small-signal NPN transistor
with an approximate current gain of 500 (such as a 2N5089) is
recommended for use with the test program below . Other similar
transistors such as a 2N3904 may also be used, but the program
may require modification .

3.3.2 Measurement Considerations

A fixed delay period of 100ms, which is included in the program,
may not be sufficient for testing some devices . Also, it maybe nec-
essary to change the programmed current values to optimize the
tests for a particular device .

3.3.3 example Program 4:

Common-emitter Characteristics

Program 4 can be used to run common-emitter characteristic tests
on small-signal NPN transistors . In order to run the program,
follow these steps:

With the power off, connect a dual-channel System Source-

1 .

Meter instrument to the computer’s IEEE-488 interface .
Connect the test fixture to both units using appropriate cables

2 .

(see

Figure 3-1

) .

Turn on the instrument and allow the unit to warm up for two

3 .

hours for rated accuracy .
Turn on the computer and start Test Script Builder (TSB) . Once

4 .

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 .
You can simply copy and paste the code from Appendix A in

5 .

this guide into the TSB script editing window (

Program 4

manually enter the code from the appendix, or import the TSP
file ‘

BJT_Comm_Emit.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:

http://www.

keithley.com/data?asset=50930

Install an NPN transistor such as a 2N5089 in the appropriate

6 .

transistor socket of the test fixture .

Now, we must send the code to the instrument . The simplest

7 .

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 .

Once the code has been placed in the instrument run-time

8 .

memory, we can run it at any time simply by calling the func-
tion ‘

BJT _ Comm _ Emit()

’ . This can be done by typing

the text ‘

BJT _ Comm _ Emit()

’ after the active prompt in

the Instrument Console line of TSB .

In the program ‘

9 .

BJT_Comm_Emit.tsp

’, the function

BJT _

Comm _ Emit(istart, istop, isteps, vstart,
vstop, vsteps)

is created .

istart

•

represents the sweep start current value on the

base of the transistor

istop

•

represents the sweep stop value

isteps

•

is the number of steps in the base current sweep

vstart

•

represents the sweep start voltage value on the

collector-emitter of the transistor

vstop

•

represents the sweep stop voltage value

vsteps

•

is the number of steps in the base current sweep

If these values are left blank, the function will use the default
values given to the variables, but you can specify each variable
value by simply sending a number that is in-range in the func-
tion call . As an example, if you wanted to have the base current
swept from 1µA to 100µA in 10 steps, and the collector-emitter
voltage (V

CEO

) to be swept from 0 to 10V in 1V steps, you would

send

BJT _ Comm _ Emit(1E-6, 100E-6, 10, 0, 10,

10)

to the instrument .

The instrument will then source the programmed start current

10 .

on the base, sweep the voltage on the collector-emitter, and
measure the respective current through the collector-emitter .
The base current will be incremented and the collector-emitter
sweep will take place again . After the final base source value
and associated collector-emitter sweep, the collector-emitter
voltage (V

), measured collector-emitter current (I

), and

base current (I

) values will then be displayed in the Instru-

ment Console window of TSB .