We have a rather expensive laser diode which is prone for ESD damage. Usually, during transport and usage it either has a metal bar bridging anode and cathode or has to be connected to the power supply to prevent charge buildup. Now, this diode had been moved into a case, with a SUB-D connector connecting it (and other vital parts inside the case) to the controller. The case usually is closed, and thereby preventing the user from attaching and removing the metal bar as long as no power supply is connected.

Therefore, we need another way of protecting the diode from sudden death due to ESD. What kind of options do we have for that? I would imagine an internal relay which either connects anode and cathode directly if no power is applied, or disconnects them and connects the diode to the power source when voltage is applied, but are there simpler options?

The driving voltage usually is around 5-15 V DC, and we have a maximum current of 2 A.

  • \$\begingroup\$ ...or has to be connected to the power supply to prevent charge buildup Do you mean that it has to be grounded? Connecting to a power supply does not help (against charge buildup) unless that supply is grounded. Also add a schematic of your setup, how it the sensitive diode used, what are its connections to the outside world (outside the box I mean)? I think you might need to educate yourself a little on ESD and how sensitive circuits are protected. This might help: electronics-notes.com/articles/constructional_techniques/… \$\endgroup\$ Feb 23, 2021 at 12:55
  • \$\begingroup\$ What protection circuitry is possible depends on what you need to connect to this "diode" and where the (vulnerable) outside connections are. If you're feeding it very high frequency signals (eg. a laser diode used in gigabit/second communications) the answer will likely be different than if it is an LED that is fed low frequencies or a microwave Gunn diode that has a DC bias supply. \$\endgroup\$ Feb 23, 2021 at 13:17
  • \$\begingroup\$ @SpehroPefhany: I added a short explanation concerning the diode type and feeding type \$\endgroup\$
    – arc_lupus
    Feb 23, 2021 at 13:56
  • 1
    \$\begingroup\$ @arc_lupus Is this diode being driven with a constant power, or is it modulated for some kind of optical communication? \$\endgroup\$
    – Hearth
    Feb 23, 2021 at 14:28
  • \$\begingroup\$ @Hearth: The diode is driven by a constant power, without any modulation. \$\endgroup\$
    – arc_lupus
    Feb 23, 2021 at 15:46

1 Answer 1


I'd guess it's something like a Gunn diode or something similar (expensive? check; ESD sensitive? check. Usually made from GaAs). Can't you simply use a TVS suppressor which is exactly designed to protect against ESD? It works like a zener, just it's optimized differently.

The shorting relay option seems a bit extreme to me.

I'd investigate the path for the ESD discharge and suppress it right at the entry point.

Just be careful to juction capacitance, it could influence the circuit (just pick the right suppressor)


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