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Calling all FAPpers - FAP800 - precautions and driving advice


New member
Nov 2, 2015
So I've been doing some digging on these forums and elsewhere, learning that these units are VERY susceptible to static. My laser has arrived but I'm reluctant to even remove it from the box knowing that I could potentially kill it. How do you guys go about handling these units? Do you always wear a static strap while handling these?

I also have another question that's sort of on the same wavelength. I have been reading over the docs regarding these and found an older application note for the LB series. On the third page is states that transients as low as 25uA can destroy the unit. Wow. I'm guessing this is why people favour linear supplies. On the other hand, I stumbled across this video where the guy appears to be powering his unit using $4 buck drivers off Aliexpress. I imagine those would be extremely noisy under load and therefore think I might be misinterpreting something here. Do any people here use a SMPS to power their FAP800? I almost bought this unit but now I'm unsure.

Also, does anyone know the thermistor plot/scale for these?
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Well-known member
LPF Site Supporter
Jan 29, 2014
I've mistreated a used surplus low priced FAP800 terribly, and it hasn't failed "yet". My understanding is they normally operate around 20-25 C, as high as 30 C for case temperature. See this: https://edge.coherent.com/assets/pdf/COHR_FAP800Series_DS_0917_1.pdf#page=3

What I've done wrong: Direct connection to 2.0 VDC Cyclon battery with no driver, being careful not to zap it with static by handling it properly, but do not have static protection or a device across the input terminal to shunt static or voltage spikes.

Would I treat a new or expensive FAP800 that way used or not? Hell no. I'm daring this one to die, trying to see if it can take this kind of abuse, so far, so good. I have a dozen of these devices, so if this one dies, it will be for a good cause, exploring the limits.

Edit: How much power output is your FAP rated for? Without knowing that, I can't suggest a proper driver for it. What value of thermistor are you wanting to know the resistance vs temperature for? 10K?


Thermistors are available in two types: those with Negative Temperature Coefficients (NTC thermistors) and those with Positive Temperature Coefficients (PTC thermistors). NTC thermistors’ resistance decreases as their temperature increases, while PTC thermistors’ resistance increases as their temperature increases. Only NTC thermistors are commonly used in temperature measurement.

Thermistors are composed of materials with known resistance. As the temperature increases, an NTC thermistor’s resistance will increase in a non-linear fashion, following a particular “curve.” The shape of this resistance vs. temperature curve is determined by the properties of the materials that make up the thermistor.

Thermistors are available with a variety of base resistances and resistance vs. temperature curves. Low-temperature applications (-55 to approx. 70°C) generally use lower resistance thermistors 2252 to 10,000Ω). Higher temperature applications generally use higher resistance thermistors (above 10,000Ω). Some materials provide better stability than others. Resistances are normally specified at 25°C (77°F). Thermistors are accurate to approximately ± 0.2°C within their specified temperature range. They’re generally durable, long-lasting, and inexpensive.
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