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Why are p-channel MOSFETs so resistive.

Discussion in 'General Electronics Discussion' started by JawadWalker, Feb 20, 2016.

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  1. JawadWalker

    JawadWalker

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    Feb 6, 2016
    So, I was shopping for high power (50V, 100A) MOSFETs that wouldn't get too hot, and I found that there were n-channel MOSFETs that were <2 mOhms but I couldn't find p-channel MOSFETs that were below 6 mOhms. Does it matter. Like, does not so much electricity flow through the p-channel MOSFET. Also, do I have to use 100A MOSFETs. Can I use say, 100 divided by 3 or 6 (the circuit has three pairs of one n-channel and one p-channel) amp MOSFETs. Here http://ww1.microchip.com/downloads/en/AppNotes/01175A.pdf is the circuit that I'm building. Thanks.
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Have a look at mobile charge carriers in N-Channel and P-Channel. Can you see that there might be more in the N-Channel type versus the P-Channel type?
    Thanks
    Adam
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The mobility of holes in a p-channel device is less than the mobility of electrons in an n-channel device. Therefore for the same geometric parameters of the transistor, the conductivity of the p-channel device is less thanfor an n-channel device.
    One can compensate by using a larger geometry (wider channel) in the p-channel device. This directly translates into a bigger gate, higher gate-source capacitance and last not least higher price of the device.
    For this reason often n-channel devices are used in the positive current path, too, which requires an extra gate drive voltage higher than the positive supply voltage of the circuit. So called "high side gate driver" circuits are available for this purpose.
     
    Arouse1973 likes this.
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