Thks for taking time to laborate on your data BenY.
Loos like Mr. Evils measured IRFP9140/240 data is not far off from yours. My question is, will the diff. VGS take off point be a concern for push-pull Class A amps? The IRFP9240/240 has closer VGS baseline, but of course, the spec comparision sheet doesn't make them a better marriage, espacially as the IRFP9240 has only half the continuous drain current (ID) value, while the IRFP9140 has almost identical output.
Also, I tried seraching for IRFP240 & IRFP9240 on www.irf.com but it seems they are not listed on the website anymore, only the IRFP9140N part is available. Are they discontinued?
Loos like Mr. Evils measured IRFP9140/240 data is not far off from yours. My question is, will the diff. VGS take off point be a concern for push-pull Class A amps? The IRFP9240/240 has closer VGS baseline, but of course, the spec comparision sheet doesn't make them a better marriage, espacially as the IRFP9240 has only half the continuous drain current (ID) value, while the IRFP9140 has almost identical output.
Also, I tried seraching for IRFP240 & IRFP9240 on www.irf.com but it seems they are not listed on the website anymore, only the IRFP9140N part is available. Are they discontinued?
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Try offsetting the gate takeoff point of the N channel with a diode.
International Rectifier stopped making them ever since Vishay started producing them.
You are overthinking this.
Texas Instruments specifies IRFP240/9240 in the datasheet example.
Maybe they know a thing or two about transistors ? 🙄 .
Texas Instruments specifies IRFP240/9240 in the datasheet example.
Maybe they know a thing or two about transistors ? 🙄 .
Matching mosfets is something I have never done.
Been designing mosfet amps since 2008 and never had any problems.
Any mosfets I use I make sure are from the same batch i.e. not some from one source and others from another source.
Feedback in the amp will iron out any differences between P channel and n channel devices.
Source resistors will iron out any differences between any small turn on voltage differences.
Been designing mosfet amps since 2008 and never had any problems.
Any mosfets I use I make sure are from the same batch i.e. not some from one source and others from another source.
Feedback in the amp will iron out any differences between P channel and n channel devices.
Source resistors will iron out any differences between any small turn on voltage differences.
)
0r22 seems to be pretty standard across medium powered mosfet amps.
Lower powered amps tend to have values of resistor.
Lower powered amps tend to have values of resistor.
I use just 0.1 ohms and buy IRFP250 Mosfets "by sticks" , 50 or 100 at the time, straight from the Importer/Distributor, so they are all same manufacturer (usually Fairchild), same batch .
They are so even , I measure between, say, 3.75V and 3.78V VgsON , that I don't even measure and label them one by one any more, go figure.
I use 4 of them for a +/- 63V rails, 300W RMS/4 ohms amp , so each passes peak 6.5A into the load, which generates 625mV drop across the ballast resistors.
As you can easily see, 30mV spread is swamped by 625mV resistor drop, it can generate a 5% error .
I can get by with that 😉
Up to 20% error would be acceptable but I'm well below that.
In fact resistor value error is around 5% and nobody complains about that 😉
Of course, if you mix batches and brands, you'd better measure and match.
They are so even , I measure between, say, 3.75V and 3.78V VgsON , that I don't even measure and label them one by one any more, go figure.
I use 4 of them for a +/- 63V rails, 300W RMS/4 ohms amp , so each passes peak 6.5A into the load, which generates 625mV drop across the ballast resistors.
As you can easily see, 30mV spread is swamped by 625mV resistor drop, it can generate a 5% error .
I can get by with that 😉
Up to 20% error would be acceptable but I'm well below that.
In fact resistor value error is around 5% and nobody complains about that 😉
Of course, if you mix batches and brands, you'd better measure and match.
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