Avtech AVR-EB4-B, Instructions Manual

Page: 24 / 83

BASIC AMPLITUDE CONTROL
The basic test arrangement for the AVR-EB4-B is shown in the figure below. The
PULSE output on the instrument mainframe is connected to the PULSE input on the
test jig (model AVX-TRR-MIX, or a customized variant) using the supplied coaxial
cable, and the control cable is connected using the supplied DB-9 cable.
Normally, the 60 cm / 2 foot-long coaxial cable should be used, except when
reflections are observed on the output waveform.
A 50 Ohm resistance (R
C
in the diagram above) must be connected to ground on
the output. This can be a discrete resistor, a feed-through terminator, or the input
impedance of an oscilloscope. If a high-speed sampling oscilloscope is used, the input
should be protected by adding attenuator on the input. In the diagram above, the
supplied 50 Ohm feed-through terminator is used to provide the required 50 Ohm
resistance.
The total effective resistance of resistors R
A
, R
B
, and R
C
in the diagram above is 50
Ohms. Thus, the voltage at point "A" is simply given by:
24
AVTECH
AVR-EB4-B
MAINFRAME
OUT
SYNC
CONNECTOR
CONTROL
AVX-TRR-MIX
TEST JIG (OR VARIANT)
OSCILLOSCOPE
(BW > 400 MHz)
TRIG
CONNECTOR
R
A
,
55.6Ω
-200V MAXIMUM
0V
+100V MAXIMUM
VOLTAGE PULSE INPUT (V
IN
)
CURRENT THROUGH DUT (I
DUT
)
CONTROL
IN
-4A MAX.
0A
+2A MAX.
REVERSE
RECOVERY
TIME (t
RR
)
DUT
OUT
R
B
,
450Ω
CHANNEL A
I
DUT
V
A
= I
DUT
× 50Ω
V
OUT
= V
A
/ 10 = I
DUT
× 5Ω
A
DB-9
CABLE
COAXIAL CABLE,
NORMALLY 60 cm / 2 FEET
IN LENGTH. SEE THE
“CABLE LENGTH” SECTION
FOR IMPORTANT NOTES.
R
SCOPE
10MΩ
typically
SUPPLIED
50 OHM BNC
FEED-THROUGH
TERMINATOR
R
C
= 50 Ω
60 cm
SMA-to-BNC
COAXIAL
CABLE