Power MOSFETs -- real or fakes..?? - diyAudio
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Old 26th May 2003, 02:55 PM   #1
AuroraB is offline AuroraB  Norway
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Question Power MOSFETs -- real or fakes..??

From time to time on these fora the subject of transistor "fakes" keep appearing. In this case, I am specifically looking at various sources for IRF and IRFP 240s and 9240s, but there is also a more general side to my question.

As it used to be also during the valve era, there will always be an "original" manufacturer of a specific transistor type. If this part gets widely used, the part will very often end up being second sourced by other manufacturers, on a licence, often with the original die films and chemistry, rather like a cooking recipee.

In my specific case, the two sources likely at hand is IR, and Fairchild. On scrutinizing the spec sheets of the two, there are minute differences in specs, but so small that in my opinion they fall under the case of normal production spread.

I do not question the fact that there might be manufacturers that do not adhere to the original spec's as closely as we wish, nor that there are situations of unlicenced copying going on also in the semiconductor industry.
I have myself seen on several occations where particularly "general substitution" parts does not work, but sometimes even commercial productions stretch the parts parameters beyond reason. An example in this cathegory could be the different hFE groups of bipolars.

Along with general comments along these lines, I would very much appreciate your comments on my specific issue, - do you really believe that Fairchilds IRFPs are inferior to the original IR..??

BTW---I do not dispute the different tempco of IRFs vs IRFPs.....
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Old 26th May 2003, 03:01 PM   #2
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"Second source" doesn't exist in real world. Check for instance BC55x and LM324 from different sources. Can differ a lot!

You should allways read the datasheets from each manufacturer.

Second source means: Parts are almost alike but usually differs in one respect, the one which makes your design to get into trouble!
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Old 26th May 2003, 03:05 PM   #3
AuroraB is offline AuroraB  Norway
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I totally agree with you that one really needs to look very closely at the different spec sheets before substituting, but " legal second source", or licence production, is indeed a reallity.
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Old 26th May 2003, 03:05 PM   #4
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somethings you want to second source -- a lot of the Unitrode controllers are licensed out to other manufacturers, International Rectifier holds many of the key MOSFET patents and licenses the product out, AMD wouldn't be around except for a licensing agreement with Intel from the 1980's.

When I sell stuff on my website (like the lateral MOSFETs or the abovementioned IRF devices) I put a picture of the original manufacturer's packaging --
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Old 27th May 2003, 04:22 AM   #5
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IRFP240
INTERNATIONAL RECTIFIER 25 TUBE
25+ :1.125
50+ :1.013
125+ :0.862

I only buy genuine IRF parts in sealed packaging from an IRF authorized distributor. One tube is only $28.

Why would you want to do anything else?

If I was driving a solenoid and used 10,000 a month I might be tempted to save $0.02 a part; but even then, that's only $200, and it might not be worth it in the long run.
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Old 27th May 2003, 09:58 AM   #6
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Quote:
Originally posted by AuroraB
From time to time on these fora the subject of transistor "fakes" keep appearing. In this case, I am specifically looking at various sources for IRF and IRFP 240s and 9240s, but there is also a more general side to my question.

Along with general comments along these lines, I would very much appreciate your comments on my specific issue, - do you really believe that Fairchilds IRFPs are inferior to the original IR..??

BTW---I do not dispute the different tempco of IRFs vs IRFPs.....

Hi Aurora,
As NP uses "...either IR or Harris..." I bet you will be on the safe
side using Harris too.

Uli
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Old 27th May 2003, 11:07 AM   #7
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Quote:
Originally posted by djk
IRFP240
INTERNATIONAL RECTIFIER 25 TUBE
25+ :1.125
50+ :1.013
125+ :0.862

I only buy genuine IRF parts in sealed packaging from an IRF authorized distributor. One tube is only $28.

Why would you want to do anything else?

If I was driving a solenoid and used 10,000 a month I might be tempted to save $0.02 a part; but even then, that's only $200, and it might not be worth it in the long run.
Maybe you don't need 25 of them!

and saving $0.02 on a part, I don't know any manufacturer who wouldn't -- provided that the present value of the inventory investment (net of obsolescence) warranted it.
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Old 27th May 2003, 06:13 PM   #8
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I have used other IR type parts from second sources, usually Harris, and they have worked fine. I do find more consistency from part to part with IR, and being the largest manufacturer of power mosfets, their prices are quite good. We have never seen any quality problems in 12 years.
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Old 27th May 2003, 06:33 PM   #9
AuroraB is offline AuroraB  Norway
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Thank you all, and NP in particular....

The reason for my question, is that on an international basis, different manufacturers have a rather various form of representation and price policies, as have also been pointed out by especially asian members of these fora.

Also, the representative agents change quickly these days, and many have fairly large minimum orders, even for registered companies, not to mention DIYers.
Luckily, I do work in the electronics field, and so have my ways around....
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Old 29th May 2003, 12:37 PM   #10
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"and saving $0.02 on a part, I don't know any manufacturer who wouldn't "

Spoken like a true bean counter.

Trying to save $0.02 on a part can create huge service problems.
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