Scientific 5000 Series, Manual

Page: 230 / 360

9
– HIGH CURRENT DECK
9-4
Version 1.23
MODEL 5000 SERIES MANUAL
For PA #1 Board only, dynamically adjust using both V
T
+ and V
T
- test @ 200 amps
with the 0.01
Ω, 0.25% resistor. Adjust R153 and R241 equally (the same number of
turns or fraction of a turn).
9.3.3 Oscillation Suppression
Oscillations are possible when testing high gain, high current transistors for h
FE
,
V
CESAT
, V
BESAT
and V
BEON
. Provision is made on the front panel of the High Current
Deck to install oscillation damping components; specifically a parallel R-L in series
with the gate (base). These components are installed in the jacks at the bottom of
the front panel provided for this purpose.
Use provided load mount plugs for coil and parallel resistor. The High Current Deck
is shipped with a 1.0
Ω resistor and 55 microhenry and 1 millihenry coil for this
purpose. These are midrange values suitable for many transistors. To check
operation, run an h
FE
test in single test measure while monitoring the A
S
terminal on
the 5000 Series Tester front panel. The voltage at this terminal should be stable
during the last 50 microseconds of the test application for the test to be valid. Adjust
the parallel R and L if necessary to eliminate oscillation.
Similarly, check a V
CESAT
test for oscillation. The h
FE
test is generally most stable with
a higher parallel R value, while the V
CESAT
test is generally more stable with a lower
parallel R value. A compromise value is attainable. The installed components are
usually satisfactory for both tests.
For devices under 100 amps, standard STI TO-3 fixtures are usually adequate as
noted in Section 9.1. For higher current devices, a pair of high current jacks is
included with the High Current Deck. Attach leads as noted in Section 9.1, keeping
them as short as possible.
9.3.4 High Deck Adaptor
For convenience, an adaptor is supplied which provides a means to program two
external resistors or other components in series with the gate (base). This allows two
separate components to be switched in for different tests. These can be used for
oscillation suppression in addition to the R-L described in Section 9.3.3. The adaptor
is schematically as shown in Figure 9-4.
If no external relay is programmed, the gate (base) is attached directly through the
adaptor. If either relay is programmed, the external resistor (or other component) is
added in series with the gate (base). If both are programmed, both external resistors
(or other components) are in series with the gate (base) lead.
To program the external relays, use the Relay Plan of the Test Program Generator in
the PCW software. In the Relay Plan, EXT R1 is programmed by entering an „X‟ in
each test step desired in the row labeled Relay 1. Assign EXT R2 similarly using the
row labeled Relay 2 in the Relay Plan (see Section 6 of this manual for more
information on setting the Relay Plan).