Electronic – How a zener and a schottky diodes protect laser diode

laserprotectionschottkyzener

I purchased a strain relief wire SR9C which has a small protection circuit for a laser diode. It says to contain a zener and a schottky diodes which protect the laser diode from ESD. By looking at the PCB board, I drew the following circuit (hopefully correct):

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Also, I managed to recognize the schottky barrier BAT54 – L4, however, I do not know what's the zener diode part is, though it says that it is a 3.3V one.

Could someone explain me the function of each of the diodes in the circuit and what kind of protection they provide and to what extent. The detailed answer would be greatly appreciated.

Best Answer

Due to the Schottky's low forward voltage drop, any (positive) ESD on the left side of your diagram will cause the Schottky to be forward biased, preventing back biasing of the LD. The Zener will clamp the forward voltage of the the LD to the Zener's breakdown voltage, in this case 3.3V, preventing over voltage across the LD.

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