This application report discusses the performance-related aspects of passive and active interfaces at the analog input of high-speed pipeline analog-to-digital converters (ADCs). The report simplifies the many possibilities into two main categories: passive and active interface circuits. The first section of the report gives an overview of equivalent models of buffered and unbuffered ADC input circuits, passive interfaces based on transformers, as well as an overview of the metrics used to gauge the ADC analog performance in addition to the entire mixed-signal chain.
The second section of the report covers interface circuits using high-speed operational amplifiers and
fully-differential amplifiers. The second section also reviews amplifier-specific performance metrics, common circuit topologies for high-speed amplifiers, and some detailed performance models that can help pick the best amplifier to achieve the desired combined performance.