what are the pros of using IRF240 9240 in amplifiers? - diyAudio
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Old 30th January 2013, 04:00 PM   #1
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Default what are the pros of using IRF240 9240 in amplifiers?

what are the pros and cons of using IRF one thing what I see the cons is it has high input capacitance to more gate current is required apart from that what are the pros of using IRF?
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Old 30th January 2013, 04:34 PM   #2
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As compared to what? You can get lower capacitance parts, but you will
be giving up something else, usually wattage or transconductance or both.

The IR parts are reliable, cheap, available, and work about as well as their
competition in the specific device categories.

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Old 30th January 2013, 04:55 PM   #3
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There is a "kink" in the distortion curve of the IRF/Vishay 240/9240 complementary devices which tends to produce a pleasantly "warmer" sound than the Fairchild vertical-MOSFET/QFET devices. Whether you view that as a "pro" or "con" will depend upon your stance in the glass-half-full/glass-half-empty/hey-who-pissed-in-my-glass? philosophical argument
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Old 30th January 2013, 07:43 PM   #4
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It isn't a kink so much that the transconductance of the IR P channel devices
shelves down about 3 dB at high frequencies, with the knee in the midband.

I included a curve on that in this article:

http://www.firstwatt.com/pdf/art_mos_test.pdf

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Old 30th January 2013, 08:26 PM   #5
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They are cheap and plentiful.

I was pleased with the sound they give.
I built an amp for disco and it always sounded good and loud.
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Old 31st January 2013, 01:18 AM   #6
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in terms of sound quality?
the P and N channel irf240 dont match properly like the other toshiba mosfets so how far this makes difference?

was that one of the reason that all aleph amps has got only one channel mosfet?

lets consider to drive 4 IRFP240 since they have high input capacitance I would like to use IRFP610 as driver for the output stages would that be sufficient?

another question is about Dynamics of the amplifier.

now who is manufacturing IRFP240 9240 Vishay or IntRectifier? I see two companies doing it. Is it one? which is good if both are doing?

how many get matched in a tube of 100? in general.. I havent tried any passdiy amps would like to try soon..

Its said especially class A amps with IRF gives phenomenal dynamics but why is this not possible in class AB.
many say that 25W of class A is too much but why so when I generally crank up the volume to 50W still be expecting dynamics out of my AB system.

Last edited by rhythmsandy; 31st January 2013 at 01:22 AM.
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Old 31st January 2013, 01:24 AM   #7
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I never bothered matching transistors and didn't have any problems.
I did use 0r22 source resistors though.

I drove 3 pairs with just mje340/350 VAS/CCS.

The P and N channel parts are quite different but it doesn't really matter, feedback takes care of any difference and none linearities.

My only criticism of using mosfets is that you lose a few volts on the output as the gates need about 4 volts to switch on.
So if you want +/-40 volts out you need +/-44volt rails.

Last edited by nigelwright7557; 31st January 2013 at 01:28 AM.
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