Power MOSFET replacements...

Discussion in 'DIY' started by QSilver, Sep 8, 2017.

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  1. QSilver

    QSilver Super Member

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    Looking for some replacement Power MOSFETs for a little amp. The originals are FX30KMJ-3 and FS30KMJ-3. I was loking at some replacements but I couldn't find any P-channel ones that could go up to -30V drain current. Would the be a problem? Wondered if anyone had some better ideas for replacements.

    The Rail voltage is 50VDC

    Best I could come up with was IRF6215PbF for the P channel.
     
  2. petehall347

    petehall347 the brandy coffee man

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  3. QSilver

    QSilver Super Member

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    I meant to say that I think with these, counterfeits are rife like with STK packs... I was hoping to just find a new part I can buy from a reputable company and know that it's gonna be reliable.
     
  4. Alan0354

    Alan0354 Super Member

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    Take a look at this one, it has a conductive tap, but if you use a silicon pad, it should work. I don't know any other details of your requirement except 30A and 50V rail:

    PMOS.JPG

    Somehow, I cannot paste the link, use the part number and go to Digikey.


    This is the datasheethttp://ixapps.ixys.com/DataSheet/DS99791D(IXTA-P-H-Q36P15P).pdf
     
  5. QSilver

    QSilver Super Member

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    I think this is the datasheet here: http://pdf.datasheetcatalog.com/datasheet/MitsubishiElectricCorporation/mXrqtxr.pdf

    But, it does say "Preliminary" and one thing that confused me was that the Source Current of -30A but the power dissipation is marked as just 35W. The amplifier is 100W per channel so something doesn't add up?

    That one looks good, but this mix up with specs is a bit confusing.
     
  6. Alan0354

    Alan0354 Super Member

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    I don't know anything about your application, you need to show the schematic first.
     
  7. VYNULADIKT

    VYNULADIKT Active Member

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    Output power is voltage multiplied by current. Dissipation is the voltage drop through the device multiplied by current. Two totally different specs. Most important is the max voltage and max current specs, as far as capability goes.
     
  8. for_p1

    for_p1 Addicted Member

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    This is right unless fevice is designed for switch mode use. It could have huge current and voltage rating, but very low dissipated power. For amplifier you need devices rated for linear work, wich is a tiny minority among power MOSFETs.
     
  9. QSilver

    QSilver Super Member

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    Thanks for all your comments. that helps a lot. I've never been quite sure of the relationship between the power output and total power dissipation required by a device. I've attached the schematic for the amplifier I'm working on. The MOSFET outputs connect to Pin 8 and 9 of each connector and are fed by the VCC+/- which is 50VDC.
     

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  10. for_p1

    for_p1 Addicted Member

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    Sorry, but I do not see FET transistors here, All are bipolar ones.
     
  11. QSilver

    QSilver Super Member

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    The FET's connect to Pin 8 and 9 of each connector. They are not on the schematic I uploaded but here is a larger schematic. You'll see why I didn't, the schematic has been badly copied and the MOSFETS are just big black squares.
     

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  12. for_p1

    for_p1 Addicted Member

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    Can you draw them by hand on original pic?

    But from what I can see - when choosing replacement, pay attention to Vgs limit. Originals have it +-20V, which is rather high. Also make sure that you will not raise power rails voltage above what was in original design.
     
  13. Alan0354

    Alan0354 Super Member

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    I have no idea what you are trying to do, your schematic has no MOSFET. You need to provide schematic and what you are trying to do.
     

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