Doc 2136-D01 Rev E 1/24/02
2-6
2-6
Fig. 2.4
Connecting laser diode and photodiode
If the photodiode should be operated with bias, a battery can be connected in series to the photodiode.
With polarity LDA grounded, connect the positive terminal of the battery to the cathode of the photodiode and the
negative terminal of the battery to pin 2.
With polarity LDC grounded, connect the negative terminal of the battery to the anode of the photodiode and the
positive terminal of the battery to pin 4.
Note:
A wrong polarity of the battery may destroy the photodiode.
2.3.4
Constant current mode (CONST I)
Procedure to operate in constant current mode:
•
Switch on the LDC 500 (refer to chapter 2.2).
•
Select a suitable current limit "ILIM" (refer to chapter 2.3.1).
•
Select the appropriate laser polarity (refer to chapter 2.3.2).
•
Connect the laser diode (refer to chapter 2.3.3).
•
Select the display "ILD" with button (18) or (19).
1
6
2
7
3
8
4
9
5
LD
PD
1
6
2
7
3
8
4
9
5
DB9
LD
PD
1
6
2
7
3
8
4
9
5
LD
PD
1
6
2
7
3
8
4
9
5
DB9
LD
PD
Note: Pin 3 of the DB9 is always at the signal ground. This allows the case of laser to be grounded for ESD protection.
