How can I increase current output for my computer controlled DAC?

[KayMan2k]

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

 

[chroot]

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

 

[KayMan2k]

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.

 

[Averagesupernova]

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.