Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Digital-To-Analog w/ 500mA

  1. Aug 30, 2004 #1
    I have taken a few college courses in EE and am putting together a pet project for a computer controlled DAC. I am using the parallel port to drive an 8-bit DAC for voltages 0 to 12V and I want an ouput current of 500mA. I have found several IC chips that allow me to do this, but only below 20mA. How can I pump up the current while mainting voltage after the DAC process? I am confused about this and any help would be greatly appreciated.

    Thnx
     
  2. jcsd
  3. Aug 30, 2004 #2

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Connect the DAC output to any op-amp that has a 500 mA output drive capability wired in voltage-follower configuration.

    There are probably hundreds available from all your favorite semiconductor manufacturers, such as National, ADI, Maxim, Linear, and so on.

    Here are a bunch of high-power op-amps from National: http://www.national.com/parametric/0,1850,695,00.html

    The LM675 looks like it would fit your needs, for example.

    Let me know if you have any more questions.

    - Warren
     
  4. Aug 31, 2004 #3
    Thank you VERY much. It looks like this will perfectly solve my problem. Just 2 quick follow up questions to fully understand exactly how to wire this up (I know how to wire a voltage-follower... just questions about Vcc for op amp).

    1) It looks like the op amp you suggested needs 16V Vcc, which is the power supply voltage I am using anyway. Should the current of Vcc be the 500mA that I am trying to boost the signal to or keep it at 18mA and the op amp will convert the volts to current as needed?

    2) I see that the maximum output of the op amp is 4A. If I put a Vcc of 800mA.. will the fan I am trying to power just draw 500mA or overload pulling 800mA?

    Again, thank you. Some of my questions may seem basic but I am trying to better understand these concepts. It is very kind of you to answer my questons in such depth.
     
  5. Aug 31, 2004 #4
    Yes the supply needs to be able to source the current that the load requires. You would be smart with a 1 amp power supply.

    Current is drawn as it is needed. When the fan starts it will draw more current than when it runs at full speed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Digital-To-Analog w/ 500mA
Loading...