Hi all,
I'm currently trying to work out what the best input drive solution to this part is for a scientific instrument digitiser. We have a couple of possible sources going into it, one is +/-10V and is easily dealt with by the inbuilt PGA. However, our other piece of equipment has a +/- 20V analog output which if I've read the datasheet correctly will probably exceed the +/-15.5v PGA limits. With that in mind I'll need to attenuate the signal somehow without distorting it. I know from past experience that there are a few main ways of doing this:
1) Resistor divider
2) Op amp with resistor network
3) Instrumentation Amp
From my understanding 1 is generally not favoured because it applies a resistive load to the input of the ADC which can mess up the conversion. In this case the PGA should act as a buffer, so maybe the simplest solution (with an appropriate precision resistor network) is the solution? 2 or 3 is what I've seen most example designs use, however I've been struggling to find an Op-Amp which has a sufficiently wide set of voltage rails to handle +/-20V inputs.
Can anyone give me some advice on how to do this without destabilising the ADS125's performance?
R Lyon
