EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Molenaar on March 30, 2016, 03:54:21 pm
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Hi all,
For a (on-off/prototype) electrostatic push-pull headphone amplifier, I need to source some linear N- and P-channel MOSFETs with a voltage rating of about 500 - 600 volt. I know a lot of semiconductors on Ebay are fake, but how big would you estimate the chance of these not so common parts being fake? Any experiences?
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Why take the chance for one-off? Buy from a reputable supplier.
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Post eBay links maybe someone can give more information, your question might be too generic.
In my experience it has been very difficult to tell that I've gotten fake chips / transistors, it's difficult to test all the characteristics.
For MOSFET's I haven't been able to tell that any are clearly fake though I strongly suspect a few.
For not-so-common parts, I would say they are more likely re-marked lower end parts / manufacturer rejects, rather than complete fakes made in a dark Chinese alley.
To give an answer I would say if they are significantly cheaper - then 70% chance they are not 100% genuine fully functional parts, otherwise if price is close to DigiKey large quantity, the odds would be 80-90% that they are legit.
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buying fake ebay parts is pretty common. there are posts all over this forum that shows pictures of little tiny capacitors (among other things) inside huge ones, to give the appearance of a huge cap that the person was trying to buy. Stupid stuff like that.
It's one thing to buy parts off ebay that only operate on low voltage like 5 volts or something, but You are wanting to buy a part off eBay, hoping it WON'T be fake, and operating at 500-600v.
I can only ask one thing....are you Crazy!?
Spend the extra, buy a reputable part from a known supplier.
On another note, if you really MUST buy a part of ebay, look at the sellers 'other' items. If they are selling Bras, dvd, other misc stuff...then stay away. If the supplier sells nothing but electronics and surplus electronics, then your chances are better that you won't receive a fake. But, that only be a small improvement on the chance.
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Are there really high voltage linear power FETs available? I thought they were limited to 200V or so.
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Mouser shows up to 1500V for a linear mosFET
http://www.mouser.com/ProductDetail/IXYS/IXTX8N150L/?qs=sGAEpiMZZMshyDBzk1%2fWi93sgdJgik587HZw1HWsLDs%3d (http://www.mouser.com/ProductDetail/IXYS/IXTX8N150L/?qs=sGAEpiMZZMshyDBzk1%2fWi93sgdJgik587HZw1HWsLDs%3d)
Up to 4500V for a non linear one.
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Thanks for the feedback. Regular distributors have a relatively high shipping if you only need a couple of euros worth. I might switch to valves though, isolated gate drive is a nice thing to have and they even look good.
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Considering the fact that LTZ1000s were being counterfeited, I wouldn't take the chance.
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For a (on-off/prototype) electrostatic push-pull headphone amplifier, I need to source some linear N- and P-channel MOSFETs with a voltage rating of about 500 - 600 volt. I know a lot of semiconductors on Ebay are fake, but how big would you estimate the chance of these not so common parts being fake? Any experiences?
50:50 - either they are fake or they aren't fake :0
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For N_channel MOSFETs at something like a 600-800 V rating, chances are good to get at least working ones. This is a very common and relatively cheap type to SMPS. Though I even heard rumors of fake 2N3055.
For the P-channel it can get more tricky - so chances to get fakes are higher. As the value is not that high, one could take a chance with a carefully checked source (not the cheapest, check other offers of same source).
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Quote from: Molenaar on Today at 03:43:30 AM (https://www.eevblog.com/forum/index.php?topic=65657.msg909376#msg909376)
Thanks for the feedback. Regular distributors have a relatively high shipping if you only need a couple of euros worth. I might switch to valves though, isolated gate drive is a nice thing to have and they even look good.
Yes, the shipping costs are a royal pain for small orders. I am always accumulating things I need to buy for projects to amortize the shipping costs.
However, trying to save few bucks on shipping by buying a very likely counterfeit part from eBay is really nuts. You are planning to operate the component at a high voltage and when the fake part goes bang on you it will do so with a lot of sparks and very likely a fire as well. I think that the resulting damage will cost you a lot more than the shipping costs for a genuine part from a major distributor.
Talk about a false economy here! :palm:
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For N_channel MOSFETs at something like a 600-800 V rating, chances are good to get at least working ones. This is a very common and relatively cheap type to SMPS. Though I even heard rumors of fake 2N3055.
For the P-channel it can get more tricky - so chances to get fakes are higher. As the value is not that high, one could take a chance with a carefully checked source (not the cheapest, check other offers of same source).
OP is looking for linear MOSFETs, not switching types. They are not at all common. I haven't even seen them on eBay.