Here, model testing steps will be shown for the VFA then external adjustments to match reported data sheet numbers will be shown
The most recent VFA FDAs focus on lower power, precision, solutions more aimed at Successive Approximation Register (SAR) and delta sigma ADC support. Those will be focus in this FDA stability discussion - but the concepts are backward compatible to the earliest VFA FDAs.
Here, an updated Loop Gain (LG) simulation approach will be first detailed and then used to show paths into, and out of, low Phase Margin (PM) conditions for a current feedback amplifier.
Emerging issues and paths to improve the Phase Margin (PM) for VFA stages that have slipped into perhaps an unsuitably low margin condition
Probably no single issue faces more high-speed signal path designers (and supplier support teams) than the risk of instability in higher speed op amps and fully differential amplifiers (FDA).