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Need op amp comparator advise

Discussion in 'Electronic Basics' started by [email protected], Jul 25, 2006.

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  1. Guest

    I'm looking for a good comparator to work as a gate drive for a power
    MOSFET. I used an LMV321 in my simulations, but I just found out the
    lead time for these devices is about 2 months.
    I'm looking at rail-to-rail voltage of 0 to 5V and I need something
    with high gain so I can switch the MOSFET quickly. The comparator
    should also be available in a DIP package. I can always try a u741, but
    I'd like to know what else is out there.

    Thanks in advance.
     
  2. The LMV321 is an opamp and wimpy both as a comparitor or for driving a FET
    gate.
    Better would be a LM393 type comparitor with something like a 180ohm load
    resistor. Basically, it's available everywhere, 8 pin dil, cheaper, more
    precise, much faster and even has better rail to rail voltages.
    john
     
  3. Rich Grise

    Rich Grise Guest

    For heaven's sakes, use a real comparator! It shouldn't be hard to
    google for a suitable one, but remember, typically a comparator has
    an open-collector (or open-drain) output, so you need to pull up its
    output. This could be a factor if you need fast switching - you have
    to size the pullup resistor to give you a fast enough rise time to
    your load, while not blowing out the output device.

    I don't know any numbers off the top of my head, but you might try
    http://www.google.com/search?q=comparator+IC

    There are other ways of getting a fast rise time, of course, like
    some kind of totem-pole, or a really fast opamp, or ...

    Good Luck!
    Rich
     
  4. Jamie

    Jamie Guest

    i've always liked the LM081/2/4 etc...
     
  5. Winfield

    Winfield Guest

    Best thing for the job might be an LM311 comparator. It's readily available
    and costs almost nothing, but it has an open-collector output and is
    active-low, though, so you'll need a pullup resistor capable of driving your
    MOSFET.

    Winfield
     
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