Matching the IRFP240 9240? how many will be wasted in ratio? - diyAudio
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Old 7th January 2013, 12:59 AM   #1
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Default Matching the IRFP240 9240? how many will be wasted in ratio?

I would like to build an amp using IRFP240 9240 pairs.
so usually how many will be wasted in an avg ratio where we could get a match to acceptable tolerances

1:20? or more?

the reason why is just to know how many to buy?
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Old 7th January 2013, 01:09 AM   #2
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The 240 and 9240 are quite different transistors so don't match very well.

However this isn't a problem in amplifiers as feedback sorts out any differences.

I have designed a few amplifiers using 240/9240 and they sound very good.

If you want to match say the 240's then I wouldnt bother as they are likely from the same batch anyway.
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Old 7th January 2013, 01:12 AM   #3
Bigun is offline Bigun  Canada
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Perhaps, in a push pull topology, differences between the n type and p type may not be such a bad thing - as the result is mostly 2nd harmonics ?
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Old 7th January 2013, 02:44 AM   #4
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its for pushpull config...

are they better than conventional Toshiba mosfets? in terms of sonic qualities?
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Old 7th January 2013, 02:48 AM   #5
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how to match? just measure the RDS with multimeter any ckt for matching these?
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Old 7th January 2013, 05:47 AM   #6
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F5 output MOSFETS matched or not?
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Old 7th January 2013, 06:55 AM   #7
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When I was matching for sextets, I needed 4 x 6 sets. I achieved this with a batch of 50 IRFP240's.
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Old 7th January 2013, 07:19 AM   #8
sajti is offline sajti  Hungary
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Quote:
Originally Posted by rhythmsandy View Post
how to match? just measure the RDS with multimeter any ckt for matching these?
No resistance measurement. Nelson Pass has some pictures how to match Your FETs. Try to search for that.

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Old 7th January 2013, 07:40 AM   #9
sajti is offline sajti  Hungary
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Check it: http://www.passdiy.com/pdf/matching.pdf

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Old 7th January 2013, 09:40 AM   #10
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h_a sells them already matched over in the swap meet forum.
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