Oscilloscope Attenuator Circuit

[specialedster]

I am trying to design an attenuator circuit for the input to a digital oscilloscope. I would like the scope to be able to measure +/- 50V, which is obviously quite large, and the specification that is causing the majority of my headaches. I would like the design to be as simple as possible (op-amp based e.g.).

So far the only way I can think to do this is by attenuating every input 10x so that it is a max of +/- 5V and then using a programmable amplifier to re-amplify a small signal that was previously attenuated (or not amplify at all if need be). This way, the rest of my circuit will be protected no matter what.

However, it seems like there should be a much easier way to do this, and I am not very good at analog design. Please help me get some fresh ideas!

 

[FvM]

However, it seems like there should be a much easier way to do this

I don't think so. There is effectively no easy way at all. You didn't mention the intended bandwidth and sensitivity, which matters a lot when choosing an optimal solution. State-of-the-art oscilloscopes have ususally mechanical relays in the input attenuators, because they can't tolerate a fixed 10:1 attenuation, and they need e.g. several 100 V input range.

 

[alexan_e]

You can check the input stages of some DSO you can find on the internet

Download the schematic from the .zip at the end of the page, there is a schematic there

(the zip link is https://www.ulrichradig.de/home/uploads/File/AVR_DSO/MyScope.zip)

Also you can find an input stage

Or Hardware Design and in the download section you can find a few schematics.

Alex