how close IRFP240-IRFP9240 to be matched?cons in mismatching.. - diyAudio
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Old 10th January 2013, 03:46 PM   #1
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Default how close IRFP240-IRFP9240 to be matched?cons in mismatching..

how close IRFP240 - IRFP9240 to be matched?
what parameters to be matched?

what are the disadvantages if not matched the result is only thermal runaway? or anything else? like sound quality degradation?

any tips will be greatly helpful...
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Old 10th January 2013, 04:23 PM   #2
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by rhythmsandy View Post
how close IRFP240 - IRFP9240 to be matched?
what parameters to be matched?
what are the disadvantages if not matched the result is only thermal runaway? or anything else? like sound quality degradation?
You asked this exact same question a couple days ago, and it was answered.
Matching the IRFP240 9240? how many will be wasted in ratio?
In fact, you got 14 (fourteen) answers.
Are you answer shopping?
Is this a joke?
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Old 11th January 2013, 01:46 AM   #3
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well that thread was that how much would be the waste but this thread is all about the cons of not matching properly..

Last edited by rhythmsandy; 11th January 2013 at 01:48 AM.
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Old 11th January 2013, 09:04 AM   #4
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You were making a c.1kw amplifier in class-A, right?

Dude, my advice: MATCH THEM CLOSELY! If you blow one, you will blow the whole thing.
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Old 11th January 2013, 09:15 AM   #5
Bonsai is offline Bonsai  Taiwan
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The short answer is they are not matched. And the P channel version has some serious issues with it in Audio.

Search for Nelson Pass 'Testing Mosfets' and do a search on this forum for comments about the issue from Charles Hansen.
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Old 11th January 2013, 09:35 AM   #6
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I think you need to articulate if you want NN PP match or if you want NNPP match. If you want the latter you have the wrong device. They are not complementary like some other fets.
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Old 11th January 2013, 02:44 PM   #7
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no not for 1kw class A ... ru kiddin? 1kw Class A... ?
its for 20W class A or 100w classAB
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Old 11th January 2013, 03:32 PM   #8
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Quote:
Originally Posted by triplej View Post
I think you need to articulate if you want NN PP match or if you want NNPP match. If you want the latter you have the wrong device. They are not complementary like some other fets.
if they are not complementary like other devices then they can never be matched right?
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Old 11th January 2013, 06:54 PM   #9
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Quote:
Originally Posted by rhythmsandy View Post
no not for 1kw class A ... ru kiddin? 1kw Class A... ?
its for 20W class A or 100w classAB

OK:
Then why do you need more than 1 pair/ch?

And:
You have understood that if you have more than 1 pair, you need to match N with N and P with P?

And:
The "matching" of N to P is done by the LME498xx...
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Old 11th January 2013, 10:06 PM   #10
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Quote:
Originally Posted by rhythmsandy View Post
if they are not complementary like other devices then they can never be matched right?
Yes. If you want to match N to N and P to P then you match the Vgs for the given bias current. That is the simplest method. The matched Toshiba fets I bought were matched to within 10mv Vgs @ 500ma Id. That was deemed to be the test limit as mesaurements lower than that were not consistent (temp variations etc). I think if you could get a match to within 10mv reliably on a home test rig that would be a good result.
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