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.
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).
The more recent Fully Differential Amplifiers (FDA) offer both CFA and VFA versionsThe CFA based versions will also have poor DC accuracy while more recent “precision” VFA based FDAs can provide much improved DC accuracy. Those VFA-based FDAs do come with some added DC error sources beyond the typical op amp terms that will be described here