1 Introduction

High-Speed/RF Analog-to-digital converters (ADCs) operate differently. The ADC analog inputs are voltage-input-sensitive devices that leave RF engineers wondering how to match the converter to the analog inputs. Adding to this confusion, analog input interfaces are typically differential by nature and host a time-varying type of input impedance as the internal sampling switch opens and closes at the speed of light or so this seems. This input impedance is thought to be a real resistive value across the converter’s input bandwidth, but when plotted on a Smith chart, the trace curve just goes around and around.