Hi, sorry for the confusion.
The laser I am using is not concerned with the voltage as long as the voltage is below it's rated value (2.6V). However, I need to vary the current value from ~100mA-~850mA due to operational purpose, so, I used a 10 ohm pot (R4). I added the 1 ohm (R5) to keep track of the amount of current to the edfa. I understand the voltage drop but since I am not worrying about the voltage, I could add R5 there.
The problem I am having is with the LM317T. I have tried several chips, but I am not getting 1.25V between ouput and adj pin no matter what.
The circuit is exactly as shown in the schematic. So, the resistors connected between the two pins (out and adj) should set the current for the load, however, since I am getting a lower(~300mV) V between out and adj pin, my current to the load is also much lower than I designed (~30-~350mA).
This is the thing confusing me. What can be the reason for me not getting 1.25V at Vref? I have tried with several LM317Ts and the result is same for all of them. I have checked the passive components as well and they seem to be fine. I am really at a loss about what the problem may be. So, I would really appreciate any suggestions on this matter.
Thank you for your time.
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I am sorry, but let me add one more thing: my problem is not that the edfa is getting enough voltage, rather it is not getting the intended amount of current. I hope my explanation clears the confusion.