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Fully Differential vs single ended.


I have a differential signal which alternates between 0 to 5V and I want to measure it with an ADC

I have three choices to do it:
1- using two single-ended op-amps and a differential ADC. 
2- using a fully differential op-amp and a differential ADC. 
3- using a single-ended op-amp to change differential to single-ended  and single-ended ADC

Which one is better?
I have to use an op-amp with a gain anyway since my ADC is 3.3V and the signal is 5V.
I would say the second configuration is the best but it is costly.
Regarding the common-mode rejection 2 and 3 removes that on the analog level but if I use two single-ended I will only rely on ADC common-mode rejection on the digital level.
I already tested AD8137YCP but it seems somehow expensive for mass production.
Please help me in this regard Thanks in advance.

  • Hi mehran,

    Fully differential is better as this increases immunity to external noise, you will also have an increased output voltage swing for a given voltage rail, ideal for low-voltage systems, reduced even-order harmonics. Another advantage is also going to be a smaller footprint on your board rather than using two single-ended op amps.