DC level shift of the common mode mode voltage to the ADC

[Junus2012]

Hello

I am working with VDD = 3.3 V, hence the reference voltage of the ADC is 1.65 V
However, I have differential AC signals with common mode voltage varying between 0.5 V to 2.5 V,
Is there an electronic circuit that simply read these signals and transfer them with unity gain amplification, only mean change the common mode DC voltage to suit my ADC?

Thank you
Best Regards

 

[KlausST]

Hi,

A diff_in diff_out ampkifier

Klaus

 

[Junus2012]

Hello Klaus
Thank you for your help,

you have solved this issue

Also I have different issue from the sensor front end and I have posted it seperately

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I am using a special type of differential amplifier, it is called a differential difference amplifier (DDF), basically it is a non-inverting fully differential amplifier

This type of amplifier has a common problem, that is the input common mode voltage should be equal to the output common mode voltage that is set by the CMFB circuit to fit to the ADC.

However, the input signals that cames from the sensor bridge has may have different common mode voltage from the VCM of the amplifier, hence my amplifier is failing to operate.

I don't want to use a typical fully differential amplifier before my DDF to fix the problem of the common mode voltage, rather I want to use AC capacitor coupling that block the DC voltage of the sensor output, and biasing the inputs of the DDF using a voltage divider circuit with the same voltage of the CMFB VCM voltage

Thanks