ILX Lightwave LDX-3412 User Manual page 20

If a feedback photodiode is used which is electrically isolated from the laser, the
feedback circuit must be resistively "tied" at some point to the output circuit. A
large resistance of 1 Mohm, connected from the laser cathode to the photodiode
anode, may be used in place of the direct connection. This is done to keep the
feedback inputs within the specified maximum +6 volt common mode voltage,
relative to the "-" laser current output terminal. The circuit of Figure 2.5 should be
used, if feasible.
01_04
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OUTPUT
P. D. L. D.
Figure 2.5 Common Laser Cathode - Photodiode Anode
OUTPUT
P. D. L. D.
Figure 2.6 Common Laser Anode - Photodiode Cathode
OUTPUT
P. D. L. D.
Figure 2.7 Common Laser Anode - Photodiode Anode
O P E R A T I O N
Installation
Module
7
+
Bias
6 +
-
9
5
3
Earth Ground
Module
7
+
Bias
+
6
-
9
5
3
Earth Ground
Module
7
+
Bias
6 +
-
9
5
3
Earth Ground
2
C H A P T E R
9
LDX-3412