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3
FL591FL LASER DIODE DRIVER
QUICK CONNECT GUIDE, CONTINUED
The FL591FL is compatible with Type A and Type B lasers,
but will not drive Type C lasers; see
Figure 3
.
Type A Laser Diode
Type B Laser Diode
Type C Laser Diode
Common
Cathode
Laser Diode Anode &
Photodiode Cathode Common
Isolated Photodiode
Short the
Laser Diode Anode
to Photodiode Cathode
Common
Anode
Laser Diode Cathode &
Photodiode Anode Common
Figure 3. Laser Type Diagrams
Recommended simulated laser loads are shown in
Figure 4
.
To determine the actual drive current, measure the voltage
drop across the 1 Ω resistor. Do not insert an ammeter in
series with the output circuit; doing so may cause instability in
the control loop.
24 Ω
1N4001
1N4001
2N3906
0.33 µF
PDA
LDA
LDC
1N4001
1N4001
LDC
LDA
1 Ω, 2 W
Constant Current Mode
Constant Power Mode
The 24 Ω resistor typically
produces approximately 30 mA
laser driver current. Vary the
resistor value to change the
output current.
1 Ω, 2 W
Figure 4. Laser Driver Test Loads
