Need circuit help for 12bit DAC offset...

Steel

I need help to incorporate the 12bit DAC into my system.

The DAC outputs 0V to 5V, and I am really needing a -2.5V to +2.5V signal, so it is the same as an AC wave.

Does anybody have any samples or links to any pages that can help me?· I have tried a few different things, but they all change the Gain, and lose fidelity of the signal...


Any help would be greatly appreciated.

Shaun

Mike Green

The general idea is that you use an op-amp with a symmetric positive/negative supply voltage like +5V/-5V or +9V/-9V.· The op-amp has a differential input and you connect the (-) to ground and the (+) to your 0-5V signal from the DAC.· You adjust the gain of the op-amp so that a 0-5V input produces a -2.5V to +2.5V output and there you are.· If your signal is not very high speed (<1MHz), pretty much any op-amp will do.· Google for LM741 circuits.· Here's one link: [noparse][[/noparse]url]http://courses.ats.rochester.edu/mottley/ECE210/WikiOpAmp.pdf[noparse][[/noparse]/url].

Paul

I found this interactive op-amp site. It's helped me solve MANY 'what-if' scenarios.·It might help.

http://www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/opamp/opamp.html?opamp=OP1177%20+/-5V

Dave Hein

Shaun,

If your signal doesn't contain a DC component, such as an audio signal, you could just add capacitor to block the DC out of the DAC. The size of the capacitor depends on the output loading and the lower frequency cutoff of your signal. If you do want to preserve the DC output, but shift it down by 2.5 volts you will need to use an op-amp.

Dave