Design Methodology for MFB Filters in ADC Interface Applications

ABSTRACT While the Multiple FeedBack (MFB) filter topology is well-known, its application to very high dynamic range analog-to-digital converter (ADC) interfaces requires a careful consideration of component value selection. This application report develops the ideal transfer function, then introduces a component selection methodology and discusses its impact on noise and distortion. The impact of amplifier Gain Bandwidth Product on final pole locations is also included, showing several examples. A complete high dynamic range, differential I/O filter for wide dynamic range ADC driving is then designed. A simple design spreadsheet embodying this design approach is available for download with this application report.