active low pass filter amplifier dc problem

[SDRookie]

I'm building a low pass filter with fully differential amplifier. For the fully differential amplifier, how could I prevent the input dc bias affect by the feedback loop? Should I add a dc decouple capacitor? Is there any method I don't have to add a dc decouple cap?

Thanks

 

[barry]

By "input dc bias" do you mean DC on the input signal or amplifier input bias voltage?

If it's the former, and you know the value of the the DC voltage and you don't want to use a cap, you can just add an offset voltage.

 

[FvM]

Please sketch the active filter topology you are trying to build.

 

[SDRookie]

By "input dc bias" do you mean DC on the input signal or amplifier input bias voltage?

If it's the former, and you know the value of the the DC voltage and you don't want to use a cap, you can just add an offset voltage.

sorry for the confusion, I mean the amplifier's input bias voltage. I build a fully differential amplifier with around 100dB open loop gain, when I connect the output to input, the output stage voltage affect the input bias voltage and the amplifier is not working anymore.

--- Updated Aug 23, 2022 ---

Please sketch the active filter topology you are trying to build.

The fully differential amplifier's schematic is similar to the figure below. Do I need to add dc bias decouple cap in front of IN- and IN+ pin?

The full low pass filter topology is shown below( please ignore the value on the schematic). The gain is about 10dB.