has anyone tried On-Semi's MOSFETS in place if IRF's? - diyAudio
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Old 27th February 2004, 02:15 PM   #1
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Default has anyone tried On-Semi's MOSFETS in place if IRF's?

Hi, I was just having a look about to see what transistors to use in my aleph-x, and I was looking on the on-semi site ofr compatable products, and it came up with their MTW32N20E as a compatable for the IRF240. At first glance this seems to be a slightly higher specced device, with a curent ratting of 32A compared to 20 for the IRF part, and an on resistance of only 0.075 ohms, compared to the 0.18 for the IRF240.

So, I was wondering if anyone had heard any of these devices before, and if it would be worth givingthem a try to see what they sound like.

???
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Old 27th February 2004, 03:17 PM   #2
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bigparsnip,

There is quite a pb with the Input capacitance

IRF240 InCap 1300 pF

MTW32N20E InCap 3600 pF

Well for a compatible.... can do better.
You'll have to find a device with a lower Input capacitance.

Regards.

Alain.
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Old 27th February 2004, 03:19 PM   #3
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Hm, I didn't check that, but as people have parlelled up quite a lot of output devices on the aleph series in the past (I'm sure I have seen over six at least), in theory the driver circuits in most designs should still be ok driving two of these without any noticable drop on HF quality right?
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Old 27th February 2004, 04:00 PM   #4
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bigparsnip,

I am building a CCS-X-BOSOZ
now, And I could take a try as it's used IRF244's in the Aleph P ; a similar setup...

I'll check where to find a pair of MTW32N20E to insert in the CCS-X-BOSOZ

they are available at DigiKey, I'll order a few on my next order , they are 8.18 cad$ each.

I expect you receive comments from other DIYer's on this.

Regards.

Alain.
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Old 27th February 2004, 04:23 PM   #5
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Quote:
Originally posted by bigparsnip
in theory the driver circuits in most designs should still be ok driving two of these without any noticable drop on HF quality right?

Thats right , and probably 2 semis will do the job of 3 irfp240 (?).

An experience: I tried Toshiba(tm) 2SK1029 ( very cheap in an electronic show) as gain device in ZENV2 and find out they were a lot more noisy than the IRFP044.


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Old 27th February 2004, 06:39 PM   #6
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Probably the ratio is more like 2 to 1. The MTW32N20E
is more like an IRF250.
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Old 28th February 2004, 03:49 AM   #7
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The IRFP244 is somewhere around $1.50 ea by the 100s from Future Active if I remember correctly. Minimum on resistance below .25 ohms is wasted unless you're building a smps for low voltages, and you'll never be able to run anywhere near the maximum current in a class A amp due to max dissapation.
Sorry, didn't mean that as a smack down, I like to think out of the box as well.
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Old 28th February 2004, 01:30 PM   #8
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The low on resistance was for my aleph-x, which will only have piddly little 17V rails (probably), so I was looking to get as much out of the device as I could (although the IRF044 has an even lower on of about 28milli ohms if I rember right, but I can't find any of those at RS).

I guess I will just have to see if I can get enough parts together to build up all four of the boards that I have, to see if I can hear any differences between the two devices. But that could take some time ...
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