US Patent 7889020 Asymmetrical filter

Disclosed is methodology and apparatus for producing an asymmetrical filter for use with implantable medical devices, and in other input filtering environments. Differing forward and reverse characteristic responses are provided by inserting a low value resistor in series with heart connecting leads so that EMI input protection may be provided without significantly reducing energy transfer from the protected device. Improved protection against voltage transients is provided with present arrangements of differentiated series impedance. Higher frequency energy is allowed out of a subject device than is allowed into such device, which allows for attenuation of undesired frequency ranges entering the filter while allowing output pulses to exit without distortion.