How to identify fake JFETs?

[myl]

Siliconix 2n5911

Plesase see attached, Please help identify are they real or not?
Thanks

 

[N101N]

They are as real as they possibly can be.

 

[egellings]

I bought what I thought was a bunch of dual N-channel JFETs for cheap, and on the curve tracer, I could not believe how good the match was between 2 devices in a can. When I put one in a diff amp circuit, the circuit did not work at all. Good on a tracer but bad in the circuit. I cut one open to find just one single JFET die, bonded out to both sets of pins on the can. No wonder the match was so good.

 

[JeffYoung]

He he... a creative solution by the counterfeiter.

 

[andyr]

I bought what I thought was a bunch of dual N-channel JFETs for cheap,

Unfortunately, these days you would be wise not to buy parts on eBay or Alibaba - but use reputable organisations like RS, Element14, Mouser or Digikey, who take care to ensure their supply lines are genuine.

Andy

 

[myl]

I bought them from Questcomp,
As I have not seen this siliconix logo like this, I asked here.
I will test and cut open 1 piece....

 

[myl]

I found that there is 2 separate fets inside one 2n5911. I use DCA 75 to test one side of the dual FET, with all other pins shorted, and the change side to test again.

 

[lucalucaluca]

Hello everybody,

recentely I got some Toshiba JFETs 2SK363-BL. They are brand new but have unusual very short legs, just long enough to solder in the PCB. I have never seen this type of leg so short. Pls, Can the experts give me information about? Are surely fake?
Thanks in advance for the reply, Luca

 

[astouffer]

Sounds like they were snipped off a board.

 

[lucalucaluca]

What you wrote makes sense to me. The legs are long only 7 mm. Just what remains after a flush cut of a board. At least they would have to be not fake if was recovered. Who snips off fake JFETs?

 

[lazybonesxp]

Hi all. I've bought a few pcs of 2SK246-GR. I am trying to check them by tracing curves.
My curve Ids (Vds):

datasheet:



What else should I measure to be sure that the transistor is genuine?

Thanks!