DN2540 plate load.

[brommermartin]

I bought some DN2540 mosfet's on Ebay but i haven't seen this print before, are these fake?

 

[Rundmaus]

Difficult to say from the outside. And looking at the inside may answer the question, but renders the answer useless.

Maybe a simple test setup which is able to drive them closely to the borders of the SOA, if the don't fail quite soon, they're probably not fake. Don't forget to mount them on a heatsink for stress tests.

Greetings,
Andreas

 

[Rod Coleman]

It's suspect.

You have the ON (onsemi) branding, but ON don't have a DN2540 or anything-2540.

Quick test: a depletion FET should have continuity from D to S when metered with DMM on 200 ohm range, even with G floating. One of my 2540s measures 8 ohm like this.

 

[artosalo]

Usually these are used as a CCS. So just build one and see how it works.

 

[brommermartin]

Hello Rod,

I measur around 9,5 Mohm

It's suspect.

You have the ON (onsemi) branding, but ON don't have a DN2540 or anything-2540.

Quick test: a depletion FET should have continuity from D to S when metered with DMM on 200 ohm range, even with G floating. One of my 2540s measures 8 ohm like this.

 

[Rundmaus]

Before using them as a plate load (as intended), I would test them intensely in a simple circuit, without the risk of damaging expensive amplifier parts.

Greetings,
Andreas

 

[SY]

Here's what I don't understand- known real parts are cheap and readily available from reputable distributors on an overnight, in stock basis. Why use EBay and dodgy sellers? It's not like these are exotic, discontinued, or expensive parts.

 

[disco]

Many European hobbyists solely use their bank account for payments while American suppliers just accept credit cards. As it seems the situation for Europeans is changing because it's possible to make a payment to Mouser via a bank in Germany, I found out a couple of months ago. Until then I had the same problem with US parts which are hardly stocked by local wholesalers (which don't sell to private persons). There's your problem

 

[Rod Coleman]

Hello Rod,

I measur around 9,5 Mohm

Sad to say, that sounds like a relabelled bipolar transistor, or enhancement-FET.

You can try it in a CCS connexion - but my guess is that it will give a current of zero, if it is the fake we suspect it to be.



Yes, in Europe, Mouser is the only practical access to any kind of franchised supply of any depletion-FET, but this works only for GBP 50 orders (in the UK) - or you pay high shipping costs.

 

[Rod Coleman]

... O, if you test it in a CCS circuit, please try the test at 30V (or 20 - 45V) first.
If it is a fake, the VDS or Vce breakdown might only be 50V.

 

[Vincent77]

I bought the same off eBay and they are fakes.

 

[Shoog]

There is a reliable reseller of these in England;

2 x Supertex DN2540N5 DN2540 Depletion Mosfet DIY CCS | eBay

Excellent guy and a member of this forum.

Shoog

 

[RollE2k]

Yeah, i have also bought from the seller Shoog link to. Great guy, and fast shipping! Plus matched is always good

 

[the_manta]

It shouldn't be a problem to buy 100 and get them sold on this forum here. As far as I see, there are no restrictions any more and these can be sold in the EU now: DN2540N5-G Supertex | Mouser

Or you use other depmosfets like these from infineon: N-channel MOSFETs: Depletion MOSFETs (60 - 600V) - Infineon Technologies

Or you simply use enhancement fets. In the cascade oder "Ring-of-two" config: http://bildarkiv.hififorum.nu/Ryssen/Pic/Rör/diyAudio-CCS-beta2.pdf

 

[Vincent77]

Mouser also sells these (and lots of other nice components), and shipping to Europe is free for orders of €65+.

 

[mogliaa]

Yes, in Europe, Mouser is the only practical access to any kind of franchised supply of any depletion-FET, but this works only for GBP 50 orders (in the UK) - or you pay high shipping costs.

Farnell sells the bsp129 at 69p:

http://uk.farnell.com/jsp/search/pr...|pcrid|13359057789|kword|bsp129|match|p|plid|

SMD but great one for CCS and gyrators, have used it with great results
Ale

 

[tricomp]

In the cascade oder "Ring-of-two" config: http://bildarkiv.hififorum.nu/Ryssen/Pic/Rör/diyAudio-CCS-beta2.pdf

This is the correct URL:
http://bildarkiv.hififorum.nu/Ryssen/Pic/Rör/diyAudio-CCS-beta2.pdf

rgds,

tri-comp