Analog differential driver

Hi there - I am looking for a good way to drive a board that takes a
differential analog -10-10V signal. I am using a current output DAC.
My current plan is to run the current output DAC through a simple
transimpedance amp (ie http://en.wikipedia.org/wiki/Image:Classic_300.jpg)
and then pipe that into a op-amp difference amplifier. That'll give me
one side, but how do I invert it? Sure, I could use an inverting
amplifier with a gain of 1, but that'd give me a delay between
transitions, which I would ideally like to avoid. Are there any good
ways to handle this situation? Maybe is there such thing as an analog
differential driver chip? When I search for such a beast, I just get
diff drivers at made by Analog. When I get rid of the Analog results I
can't seem to find anything. I can't imagine this is *that* uncommon
of a problem. Suggestions? Argh.

-Michael

 

Hi there - I am looking for a good way to drive a board that takes a

Don't google for "analog differential driver", just for "differential
driver" or "differential line driver".

There are many differential drivers, from different manufacturers. I can't
really pin out just one of them, you'll have to compare datasheets and see
which one is good for your circuit.

Or, you can build your own differential driver using regular opamps. It's
not that complicated.. One opamp does noninverting buffering/amplification
for + signal. The other one is connected as inverting opamp, doing the same
buffering/amplification for - signal. So, it's symmetrical (enough).

Using reasonably fast opamps, there's no delay that would have any effect.
Unless you are using signals which are very fast (like hundreds of MHz).

 

Does the dac have diff current outputs? What's its part number?

How fast does this need to be?

John

 

Right, you just need to *know* how to do it...

 

The standard way of single ended to the differential conversion is using
the two identical differential amps. One is inverting the signal, the
other is not inverting. This provides for the completely symmetrical
configuration. The full differential opamp may be used for that also,
however there are not too many opamps of this kind.

You can also find some interesting topologies here:

http://www.edn.com/article/CA302234.html

Although their configurations are not strictly symmetrical.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com