2SK1420 replacement?

Discussion in 'General Electronics Chat' started by hazim, Sep 19, 2010.

  1. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    Hi all,

    In a car audio amplifier, there are four MOSFETs for the amplification, they are K1420. I just want to know if IRF540 is a good replacement or no.
    comparing both mosfets datasheets, I found that IRF540 exceeds the k1420 in the main power, current and voltage characteristics, but rds(on) of IRF540 is about 0.07Ω while it is 0.04 for k1420. Also the rising and falling time (on & off) differs to about twice..
    Any help?

    Regards,
    Hazim
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    The STP36NF06FP is listed as a cross reference.
     
  3. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    Right, but I'm asking about IRF540 specifically.

    Regards,
    Hazim
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    I'll leave it to our FET expert, I'm sure the gate charge requirements are going to need to be very close. While I don't know about a Class D amp, the biasing requirements of a common BJT amplifier is a sensitive matter.
     
    hazim likes this.
  5. Audioguru

    New Member

    Dec 20, 2007
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    The on-resistance of the IRF540 is nearly twice as high so its heating will be nearly twice as high and the output power will be less.
     
    hazim likes this.
  6. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    I was thinking about this. I tried to use irf540 for testing (at low volume and with attention to the mosfets' heat, the amplifier still not working, there should be another problem I didn't found it yet.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    You must find the problem that caused the original Mosfets to fail.
     
  8. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    I tested all the capacitors, diodes, transistors and some resistors (gate resistors+...), all of them are good. The Mosfets and diodes with on the heatsinks have thin insulation 'paper' in between, the owner of the amplifier told me that it's more probably that some insulation papers were displaced and a short circuit happened and the Mosfets burned out...

    I tested the voltages on the circuit board randomly on parts, more than half of the board seems not having the supply voltage connected. All copper paths and solder are ok. I'll try to find the problem tomorrow.

    Regards,
    Hazim
     
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