EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: JohnnyGringo on August 30, 2013, 04:06:23 pm
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One seller has 100 2n3904 NPN Transistors for $10.48, another seller has 10 for $7.70.
No datasheet/manufacture information on the 100 pieces. The 10 pieces are Fairchild Semiconductor Part Number: 2N3904BU. (BU is just BUlk quantities)
Would you expect the no-name ones to have the same (or "close enough") characteristics as the Fairchilds?
In general, is it best to stay away from the no-names? Would you expect equivalency with passives and ICs, etc. ?
Yes, I know, it's only a couple of dollars in this particular instance, but in general... ?
-Thanks !
John
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if you are just using these in saturation, like to turn on a relay it doesnt matter.
if it is in a precision analog thing you need datasheets and check all specs...
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There have been some reports of fake power transistors, though I'm not sure how prevalent this is. A Fairchild transistor from Digikey is less likely to be fake than a nameless transistor from a random broker.
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I see.
But assuming no fakes or fraud, would you expect 2N3904s from one manufacture to be different from another one's? I.e. Fairchild's vrs TI (if they even make one)
Sorry, I'm not actually trying to be dense, it just comes naturally.
-John
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The 2N3904 is a generic part that is made by many, many vendors. The specs are not hard to meet, so there is not much money to be saved by cutting corners.
On the other hand, the prices you quote are pretty poor. Why take a chance when you can buy genuine Fairchild parts from Arrow for $0.0185 each:
http://www.findchips.com/avail?part=2n3904bu (http://www.findchips.com/avail?part=2n3904bu)
Even if you don't buy anything else from them to amortize the $8 shipping, your total cost for 100 parts would be less than the eBay seller.
(And BU means bulk pack - loose parts in a bag - as opposed to tape and reel or ammo pack. It's more convenient for hobby use.)
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They should all meet the minimum specs, but that doesn't mean they are identical. Especially for a jellybean part some manufacturers could easily take a superior transistor and label it as 2N3904. There's no law that says that a transistor rated for Ic = 200 mA must self-destruct at 201 mA. This can get interesting when replacing old parts that assumed a much lower fT, for example.
In general the datasheet specs will be almost identical, so as long as you only rely on those you should be fine either way.
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http://uk.farnell.com/fairchild-semiconductor/2n3904/transistor-npn-40v-200ma-to-92/dp/9846743 (http://uk.farnell.com/fairchild-semiconductor/2n3904/transistor-npn-40v-200ma-to-92/dp/9846743)
http://www.newark.com/fairchild-semiconductor/2n3904/transistor-npn-40v-200ma-to-92/dp/95M9196 (http://www.newark.com/fairchild-semiconductor/2n3904/transistor-npn-40v-200ma-to-92/dp/95M9196)
get 1000...