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Electronically divide voltage signal (sim to differential amplifier)

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May1-14, 01:27 AM
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Quote Quote by berkeman View Post
I didn't read through your links -- is the bandwidth of the Vref input specified in the datasheets?
I design ADCs for a living. Most of the parts I design have the Vref inputs (they are almost always differential) heavily bypassed internally. Vref is designed to be as close to DC as possible to reduce noise (and improve vref stability). So, unless the signal connected to Vref were step-wise DC, it wouldn't work very well on a lot of modern ADC designed for high-speed signal processing. Other parts have a fast reference buffer on-chip that would have a much higher bandwidth. This is typically not specified on the datasheet.

There are certainly ADCs that are designed for this kind of application, but buyer beware.

I'd just sample the signals and do the subtraction in the digital domain.
May1-14, 04:08 AM
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It would be interesting to see some details (block diagram) of how both the cases of |VA|>|VB| and |VA|<|VB| are dealt with, when one of them is the Vref of an ADC. Is there no lower limit to the possible range of Vref for the device to work correctly? Is it possible to deal with that problem by offsetting reference and input volts and yet still get the 'right answer'? I can't see the arithmetic working properly.
The link, provided by Baluncore seems to be for a device that will give the ratio of two Resistors and not voltages, in the way that is required by the OP. Have I got this wrong and how can the device be used for Voltage division?? [Edit: I didn't put that in the right way. I realise the device measures volts but still the ref voltage needs to be kept 'more' than the input]
I feel inclined to go along with analogdesign's ("professional") opinion. He would appear to know a thing or two about the business - from first hand. There is something about Symmetry in design that is appealing and reassuring, which is why the use of two ADCs would seem to be the best way to go. Are they really that expensive (compared with the MSC1211, quoted)?
May4-14, 06:05 PM
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