Have you ever wondered how well a given component (voltage regulator, operational amplifier, ferrite…) could filter the noise coming out of your power supply? Limpkin’s blog provides an analysis.

In theory all of these components’ datasheets should provide you with a figure of merit, typically the Power Supply Rejection Ratio (PSRR). But what tool should you use to make sure reality matches theory? Answer: a Line Injector.

A line injector is a relatively small device that is inserted inline with your power supply lines to inject any kind of perturbation signal.
By measuring the perturbation signal before and after your Device Under Test (DUT) you can then deduce how good the DUT is at filtering out unwanted noise at different frequencies.

See how such a device made and used in the post here.