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Ruining mosfets with a transistor tester and tweezers

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--- Quote from: magic on April 18, 2024, 08:40:18 am ---It's not ESD damage, it's 100μA or more of AC current pushed through the gate continuously for a meaningful fraction of a second.

It's absolute nothing for any device with built-in ESD protection, but unprotected discrete MOSFETs are destroyed immediately and for good. I personally blew a few 2N7000 and some other type I forgot this exact way (except it wasn't the transistor tester but other circuit powered by a wall wart). The outcome was the same - fairly low resistance between source and drain, permanently.

--- End quote ---

No need to argue about that, but the thread initiator asked if just handling with bare hands and tweezers makes a FET instantaneously going to heaven. That´s hardly plausible.

Of course, a 110V-AC-0.5mA source (like typical wall warts relative to ground) can be FET-lethal - especially for the small devices with low Ugs-rating.

EDIT: I´ve just read that the OP has used the transistor tester while powered from the wall wart. In that case, I suppose he has destroyed the TO220-power-transistors by an AC current from the wall wart over the cooling tab through his body to earth. The 2N7000 may have survived due to their plastic case that easily withstood this comparatively low voltage... Just as a possible explanation.

EDIT2: If possible, always use these transistor testers battery powered. This parasitic power supply current may also be quite dangerous for the 328-tristate-inputs and last but least it´s just a source of noise that just can be avoided.

Thank you all for your helpful replies and detailed discussion on the subject. So much to learn!
By the way - It's good that those were budget Ali MOSFETs, not the real expensive ones ;)


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