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Old 25th January 2010, 07:37 PM   #1
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Default Which mosfet is best???

I have made a copy of the MINI A-J Per Juma's recommendations and when I went to grab my tube of IRFP240's I couldnt find them.Right now they are hard to buy from the usual sources .I have some irfp044 which list a typical input capacitance of 2500pf. High compared to the 240's which are listed typical 1275pf. I also looked at 250's but the spec is high similiar to the 044's. Irfp140's are available . Please help me decide what to do,what to do!!!
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Old 25th January 2010, 07:46 PM   #2
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To clarify , I substituted 2sj74's for the BF862 devices and reversed polaritys where necessary .Hence the use of N-channel deices in the outputs. I tried to work with the BF862 things but eyesight and manual dexterity defeated that endeavor. Someone is soldering them for me but have not received them yet. Sometimes DIY can be trying.!!
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Old 25th January 2010, 08:58 PM   #3
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Quote:
Originally Posted by sandyhooker View Post
I have made a copy of the MINI A-J Per Juma's recommendations and when I went to grab my tube of IRFP240's I couldnt find them.Right now they are hard to buy from the usual sources .I have some irfp044 which list a typical input capacitance of 2500pf. High compared to the 240's which are listed typical 1275pf. I also looked at 250's but the spec is high similiar to the 044's. Irfp140's are available . Please help me decide what to do,what to do!!!
I have no problems sourcing IRFP240/9240 in the UK

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I use the 240's in my multi MOSFET output stages.
I sometimes use the 250 if only using a single output pair.
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Old 25th January 2010, 10:01 PM   #4
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You might consider the Toshiba 2SJ201 and 2SK1530.

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Old 25th January 2010, 10:03 PM   #5
juma is offline juma  Germany
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Sandy, if you are using 2sj74 and N-channel MOSFETs then it's standard Aleph-J that you have.
"Mini" might mean that you use somewhat lower PS voltage and/or bias, right?
See if you can find IRFP140 or IRFP140N and you'll be fine
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Old 26th January 2010, 03:22 AM   #6
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> You might consider the Toshiba 2SJ201 and 2SK1530.

Meaning you already tried them ..... ?



Patrick
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Old 26th January 2010, 03:47 AM   #7
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Quote:
Originally Posted by Nelson Pass View Post
You might consider the Toshiba 2SJ201 and 2SK1530.

Spittin'Lama did a lot of work with those babies and they were like the Sammy Cahn/Jimmy van Heusen song of a few years back.

Ain't seem Lama in a while.
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Old 26th January 2010, 06:05 AM   #8
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Juma-my little board has your LED driven current source ..otherwise pretty much the same as an Aleph-J but with 15volt rails.

The devices suggested by Mr.Pass are premium in nature and quite expensive.I started this project because I needed a small amp to hang on the back of a computer and because I thought I had all the goods to makei it. I had made one of the Grey Rollins variety which was just fine..gave it to one of my offspring and could'nt possibly get it back.

Nick Pappas is soldering up the BF862 devices on the little boards that Juma sent..when they come back I'll make the second channel with them.

Noticed on the 2sj201 listing" ChargeRate@ VGS10v" measured in Nanocoulombs
and different makers listed different numbers. I suspect the smaller values are prefered.

Thanks all for the useful comments.
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