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I am a newbie at analog design, and trying to design a laser diode driving circuit and TEC cooling circuit for a 14 pin laser diode, such as P1550-ADF-B: 1550NM ADF LASER DIODE which has forward current of 500 mA and forward voltage of 2.5 V. First question rises here.

1) Can I drive the laser diode just by supplying 500 mA to Anode such as using a lm317 current limiter circuit? Will the voltage on the laser diode be adjust itself to 2.5 Volts? The voltage regulation circuit I am thinking of using is the one below.

Lm317 current regulator

The reason I want to use LM317 similar component is to be able to use the driver for other same type butterfly packages that want less current like 200 or 300 mA.

Resulting from question 1.

2) If I need also the voltage regulation. I'm thinking of connecting the output of LM317 current regulator to a ultra low dropout voltage regulator, such as NCP176, also because LDOs give very smooth output. I think in theory, I can fix the output voltage from ULDO Voltage regulating circuit and the current going in to the ULDO circuit is determined using LM317 Regulator which hence limits the output current to feed the laser diode. * NCP176 also has, Built−in Soft Start Circuit to Suppress Inrush Current for starting up the laser.

NCP176 Typical Application from datasheet

At last for TEC circuit; I found a control circuit from Tyco Electronics laser diode dahasheet.

Thermo Electric Cooling Control

Simulation result of TEC circuit;

pSpice simulation

For now, cooling part seems like it would work to me.

If you guys can answer my questions at 1 and 2, or share know-hows I would appreciate it. Thanks in advance.

The last state of the schematics is like below;

Altium Schematics

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