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Using a P-Type Mosfet

Discussion in 'General Electronics Discussion' started by alexm865, Feb 12, 2009.

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  1. alexm865


    Feb 12, 2009
    Hi All,

    I need a bit of advice about using a P-Type Mosfet. I've mainly dealt with N-Type Mosfets being driven from the low side of a load but in this case I need to operate a load from the high side using a P-Type Mosfet.

    I've searched through my old Uni Notes and I'm still not sure whether I can operate a P-type Mosfet using the same voltage at the gate as what I'm trying to switch at the load.

    The load is inductive (an ignition coil) and is being driven from a pulsed 12V source (see the attachment for the circuit details). The P-Type Mosfet I'm using has a protection diode built into it (so hopefully it won't blow too easily!).

    My question is can I use a P-Type Mosfet to switch 12V to the Load from the high side (see the attached circuit) using a 0/12V pulsed gate signal into the Mosfet.

    The reason I do not want to drive the ignition coil from the low side using a N-Type Mosfet is because I would have to invert the gate signal going into the Mosfet for the ignition coil to fire properly. I could use a NAND gate to invert the signal or a Mosfet Driver but I would like to keep the circuit as simple as possible (less things that can go wrong!) and I would need components that can operate safely at temperatures over 100 degrees Celsius (which the IRF9540N P-Type Mosfet can do so).

    Any advice on how to use the P-Type Mosfet would be most helpful.



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