Oscillators and Frequency Response Measurements

The primary tool needed to test and characterize a power supply design is the oscilloscope. But most oscilloscopes have limited utility if you want to perform frequency response measurements like power supply rejection ratio and control loop response.

In the past, to take these measurements, the embedded engineer had to rely on special low frequency network analyzers. Today, there are a number of oscilloscopes which allow you to perform these measurements automatically. These oscilloscopes have a built-in arbitrary waveform generator, which is essential for taking these measurements.

They also contain integrated power analysis and measurement software, which makes the set up simple and makes it easy to take measurements with time. They allow you to customize important parameters and automate calculations and see results and not mere numbers. Custom power supply makers have come to depend on these modern oscilloscopes, thanks to the benefit they confer.

Note that the accuracy and dynamic range of these new devices are not as good as a low frequency network analyzer but it is usually good enough. For example, when you are designing a linear power supply with a low noise DC output, these modern oscilloscopes can easily track the power supply’s characteristics, as well as a low frequency network analyzer.