Filtering and fast transient response

摘要

Power architects engaged in designing systems requiring low output noise and fast transient response - such as RF transmitters, power amplifiers, test systems, displays, designs supporting low-voltage ASICs, and laser-diode transmitters - understand that when attempting to tailor power systems to meet both requirements using passive components, the two objectives become diametrically opposed. Minimizing periodic and random deviations (PARD) requires filtering, whereas fast transient response is impeded by filtering. This article demonstrates how an active filter-when paired with a typical off the shelf dc/dc converter-will not only provide superior filtering compared to the passive approach, but will also provide improved transient response. This can either eliminate the need for load capacitance altogether for noise reduction, or reduce the amount required by as much as a factor of 10 for equivalent transient capability.