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Driving a FET with Arduino

  1. Apr 17, 2013 #1
    I want to drive a IRFP250N power MOSFET using a square wave generated by an Arduino at high frequencies, maybe 1kHz or so. I doubt I can hook up the digital out to the mosfet gate, so is there some kind of gate driver I can make/buy that will take in the square wave signal and violently switch that mosfet on/off at the proper Vgs (I think 4V for the 250N) as fast as possible?

    thanks
     
  2. jcsd
  3. Apr 17, 2013 #2
    The Gate Threshold Voltage you see in the datasheet is really an "off"-characteristic and is where you'll start to see the on-resistance of the FET begin to drop.

    For the IRFP250N, a V_GS of 10 to 15 V would decrease its on-resistance substantially, e.g. they use 10 V for the test circuits in the datasheet. You should have a look at the output or transfer characteristics of the FET instead to determine what gate voltage you should drive it with.

    Even for the IRFP250N, with its relatively large input capacitance, 1 kHz isn't really that high. Does your Arduino board have open-collector/drain outputs? How much current can it sink through its output pins?

    You could throw in a push-pull stage yourself to drive the FET or you could just pick one of the simple drivers from Linear/TI/Fairchild etc.
     
  4. Apr 18, 2013 #3
    I am trying to do this as well. Do you have any specific components that you recommend? How about this one: UC3710

    Fairly expensive but is it worth it?
     
    Last edited: Apr 18, 2013
  5. Apr 19, 2013 #4
    The UC3710 is maybe a tad overkill for driving a IRFP250N at 1 kHz. If price is a concern, I'd just have a look at whatever was cheapest in a DIP-package (if you have to solder it yourself).

    I did a quick search on Farnell and this was the cheapest in my country (Denmark):
    http://ww1.microchip.com/downloads/en/DeviceDoc/21390d.pdf

    Pop that one in with a 22 ohm resistor in series with its output and I'm sure you'd be fine.

    Edit:
    You'd need a supply capable of feeding it and some decoupling caps, but I hope that goes without saying.
     
  6. Apr 19, 2013 #5
    Why not just use an npn transistor in a common base configuration with a higher voltage supply?
     
  7. Apr 19, 2013 #6
    See attached for common base level shifter for Arduino.
     

    Attached Files:

  8. Apr 19, 2013 #7
    Low input impedance and high output impedance, isn't that the opposite of what you're looking for in a driver?

    I guess you could solve it with buffering, but why not just add a matched pnp for a totem pole instead?
     
  9. Apr 19, 2013 #8
    Are you trying to make a philosophical argument or are you stating that an Arduino can't drive a 10k load and a 51k source impedance can't drive a mosfet?
     
  10. Apr 20, 2013 #9
    I'm saying you probably wouldn't use a common-base amplifier to drive a power MOSFET since it loads the input to charge the FET's gate capacitance.

    Edit:
    Having had a look at some of the commercial Arduino boards from arduino.cc, the digital outputs can source/sink 40-50 mA per pin according to their specifications, so your solution would probably work fine. I'd personally rather use a push-pull stage instead for the larger current drive and to avoid loading the Arduino.
     
    Last edited: Apr 20, 2013
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