Sensitivity of fast settling PLLs to differential loop filter component variations

摘要

An operational amplifier configured as a combined differential amplifier and integrator may exhibit a transient response which can be catastrophic to a phase-locked loop (PLL) intended for fast phase settling. A practical mathematical model for the loop filter is derived, and corresponding effects are shown in a frequency synthesizer by means of computer simulation and empirical data. Phase settling is shown to be sensitive to small variations in the loop filter components, well within the device tolerances.