Siliconix Mosfet -vs- p-channel issue ? - diyAudio
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Old 6th September 2015, 04:02 PM   #1
pwan is offline pwan  United Kingdom
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Default Siliconix Mosfet -vs- p-channel issue ?


I recently acquired a big lot of IRF9610s with Siliconix logo with marking "Y32K AA" and the number 26 in small circle. Those 9610 are planed to use as VAS.

However,I just found what Charles Hansen mentioned about the P-CH issue in 2004 (below). I did search and found that both IR and Siliconix were acquired by Vishay.

How can we know if my 9610s also have the 'misbehave frequency response in audio band' as Charles mentioned? Any quick & basic testing for that?

Thank you in advance.

Originally Posted by Charles Hansen View Post
Hello -
... When we were selecting the devices to use in that design we found a funny thing with all of the International Rectifier P-channel devices we tested.

If you put them on a curve tracer, the forward trace and the return trace did not overlay at all. After running several experiments we found that their transconductance would shift in the first few milliseconds after Vgs was changed. This shift was not small, but on the order of 10% to 20%. You will note that the time constant of this effect put the misbehavior right in the middle of the audio band.

This was behavior was found on every single IR P-channel device we tested, using at least 5 samples each of 5 different part numbers. No other manufacturer's devices exhibited this behavior, including Siliconix, Motorola (now On Semi), Harris (later Infineon and now Fairchild), and at least one other I can't recall now.

Charles Hansen
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Old 6th September 2015, 04:33 PM   #2
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Charles Hansen is actually saying that Siliconix or any other manufacturer's P channel devices do not have the issue noticed only with IR manufactured ones.
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Old 6th September 2015, 04:43 PM   #3
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It is not certain whether the parts you have will exhibit this shelving
phenomenon. I have seen at least one case of another brand having this,
probably due to using IR dice or the same process. I have also seen examples
of IR P channels which did not do it.

Charles and I have described this from different angles due to the tests -
he viewed it on a curve tracer, I measured transconductance vs frequency
under different conditions of voltage and current. He described it as small,
on the order of 10% or 20%, I was seeing more than that, as much as 50%.

In the end, you should test the parts. You can take a look at my 2004
article on testing Mosfets, found on the First Watt website and at PASSDIY,
and you will note the test setup and also the example of IRF9240 showing
this character.

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