Solutions for radio frequency electromagnetic interference in amplifier circuits from Microchip, app note can be found here:
EMI is a real problem today and it can affect most electronic devices, including medical and avionics equipment. Modern devices include EMI filters to ensure the proper operation of equipment in harsh EMI environments.
This application note demonstrates that the EMI-hardened op amps are more efficient in rejecting high-frequency EMI than standard op amps. It also shows how standard op amps can reject EMI using external filters.
Several examples have been used to demonstrate the EMI performance of Microchip amplifiers, and to discuss how EMIRR is measured and characterized.