MOSFET and FET control of solenoid

Discussion in 'The Projects Forum' started by weirdyboy, Dec 23, 2008.

  1. weirdyboy

    Thread Starter New Member

    Dec 19, 2008
    1
    0
    I'm currently designing a circuit to control a solenoid, (1A peak, 0.12A hold, 12V, 50 Ohm resistance, 54.9mH). I'm using a SI3443BDV P-Channel Mosfet with 12V connected to the Source and the positive of the Solenoid to the Drain. The gate is connected to the drain of a 2N7002 FET, which allows the solenoid to be switched on from a TTL Level signal from an FPGA.

    I've attached a diagram of the circuit.

    My question is, have I missed anything. Or is the circuit ok before I commit to buying parts and getting the layout done.

    This is my first posting, so thanks in advance of any responses I may get.
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    This is usual way a high voltage load is driven controlled from a low voltage signal. Your power MOSFET can only take max. of 12V Vgs so a voltage divider is added.

    [​IMG]

    Do you have a particular reason to use MOSFET for the 3.3V logic? Check the 2n7002 datasheet and note that it can only drive a few mA at Vgs=3.3V. This may not be enough for fast turn on for your power MOSFET.

    Therefore you have to select another MOSFET that fully turns ON at 3.3V, not 2n2007 though.
     
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