you can add large capacitor in parallel with the supply voltage , the noise in the supply voltage can come from the supply itself like during converting from A.C to D.C. The noise can also couple from the circuit to the supply in case of the digital circuit switching operation, therfore it is recommended to set up the ground of the analog from that of the digital
The source of the noises are diverse with out knowing if we cannot rightly point to the solution, But if it is a AC ripple then the capacitor can smoothen it out for you
you can add large capacitor in parallel with the supply voltage , the noise in the supply voltage can come from the supply itself like during converting from A.C to D.C. The noise can also couple from the circuit to the supply in case of the digital circuit switching operation, therfore it is recommended to septet the ground of the analog from that of the digital