How to design a differential input ADC?

[yiyin]

Hi, I have met a problem in designing an A/D converter used as mulit-biit
quantizer in a sigma-delta modulator.

The input signal is differential and with about 0.5V common mode voltage
the output should be in thermocode format

I don't know how to handle the differential input
only find one paper about this in IEEE
using resistor ladder to convert current into voltage
but in my case the input is voltage
I calculated and found it's not linear to use this structure for a voltage input

Is there anyone has experience in desing this kind of quantizer?

Thank you in advance for your help.

 

[IanP]

Can you handle single A/D input ..
Maybe you can take 2 single inputs and treat them as differential .. ???

 

[yiyin]

Can you handle single A/D input ..
Maybe you can take 2 single inputs and treat them as differential .. ???

maybe it's a good solution, thank you

Fortunately I found a circuit in a PhD thesis and it works
it transfers differential voltage signal to current and use the current to control
transistors