Keithley 2520, User Manual, Page: 289 / 329

Model 2520 User’s Manual Measurement Considerations F-5
Figure F-3
Rise time of 0.45A current pulse
Increasing cable length
To double the effective recommended cable length without significantly degrading pulse
characteristics, connect the laser diode to the CURRENT OUTPUT HI jack only. To use
this method, connect one laser diode terminal to the center cable conductor, connect the
other terminal to the cable shield, and install a BNC
shorting cap on the CURRENT OUT-
PUT LO jack. Select negative current source polarity if the laser diode anode is connected
to the center conductor; conversely, select positive current source polarity if the laser diode
anode is connected to the shield.
This method decreases rise time because it eliminates one of the two cables that connect
the current source to the laser diode, effectively cutting the cable inductance in half. How-
ever, the disadvantage is that one terminal of the laser diode is connected to analog com-
mon, and you must be careful to properly set the polarity as covered above. Also, this
connection method should not be used for the VOLTAGE SENSE terminals.
0.45
0.5
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0 1 1.5 2 2.5
Current
(A)
Time (
µ
s)
0.50