I'm starting a new thread devoted to sharing experience with questions related to genuine and counterfeit parts.
I'm reserve this first post to help build navigation in the thread to various posts by adding links to the start of various discussions.
I'm sure this is a "repeat" of many other threads on the topic, so feel free to link to other posts/threads on the forum.
I'm reserve this first post to help build navigation in the thread to various posts by adding links to the start of various discussions.
I'm sure this is a "repeat" of many other threads on the topic, so feel free to link to other posts/threads on the forum.
I understand your candor @WhiteDragon in that you're implying there's a lot of folks with subjective opinions and I understand that. The hope is we can make this thread more about objective approaches. The goal here is to share knowledge and experience on how to avoid buying counterfeits in the first place, and identifying them if the former didn't occur in time.
The first relevant post here is regarding determining if parts acquired are Genuine Harris IRFP9140's, or fakes/counterfeits. Below are some images and basic measurements. The date code from '96 to '97 still falls within when Harris was a company prior to being bought by Interstil, but it sure is a clearly different approach to markings from one year to the next. Additionally, the "MALAY" marking is different on the "press" marking indicating a different fabrication line.
I'm curious if anyone can confirm that the laser engraved version here has any chance of being legit. I realize Vgs can vary, so is there any way to clearly know if a part is fake via measurement? I'm willing to give various circuits and measurements a try.
Images below taken from a stereo-microscope and hence the color difference from above.
The first relevant post here is regarding determining if parts acquired are Genuine Harris IRFP9140's, or fakes/counterfeits. Below are some images and basic measurements. The date code from '96 to '97 still falls within when Harris was a company prior to being bought by Interstil, but it sure is a clearly different approach to markings from one year to the next. Additionally, the "MALAY" marking is different on the "press" marking indicating a different fabrication line.
I'm curious if anyone can confirm that the laser engraved version here has any chance of being legit. I realize Vgs can vary, so is there any way to clearly know if a part is fake via measurement? I'm willing to give various circuits and measurements a try.
Images below taken from a stereo-microscope and hence the color difference from above.
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Be interesting to see where this thread goes, sort of 
. My experience is, I've been buying "cheap" semi's online for over 20 years. Not one fake. Bin ends, seconds, faulty, out of spec - yes. Fakes? No. I think the whole fake semi's thing is completely exaggerated. Sure some long extinct expensive semi's are ripe for the picking but some here say they receive fake transistors that are worth literally cents and in current production, or that ON Semi is fake etc. etc.
. My experience is, I've been buying "cheap" semi's online for over 20 years. Not one fake. Bin ends, seconds, faulty, out of spec - yes. Fakes? No. I think the whole fake semi's thing is completely exaggerated. Sure some long extinct expensive semi's are ripe for the picking but some here say they receive fake transistors that are worth literally cents and in current production, or that ON Semi is fake etc. etc.
You had to be lucky enough. Today even fake microcontrollers or specialized ICs are common.
By measuring transcoductance over several frequency points. Method is described in the attached article at page 5. Transconductance should remain almost the same. International Rectifier’s IRFP9140 has a gradual drop starting from 200 Hz and shelving at 1 kHz.
There is another markings and logo version of the genuine Harris IRFP9140, probably produced after 1998, when company logo was changed to slanted letters. I’ve just measured them using mentioned article and Gm doesn’t change over frequency. Input capacitance and threshold Vgs also conform to datasheet specifications.
Quite possibly. I think too buying transistors as opposed to rare uP's helps. Ironically the last purchase I made were IRFP 140's / 9140's. Genuine IR's but the 140's had very low VGS on whereas the 9140's were normal. Be fine for a regulator but not a PP amp as intended. They were 1/4 the price from Mouser so I took my chances... and lost.