Power Supply Measurement Techniques Using Picotest Signal Injectors

Focus:

In this 3 minute video, Tom Boehler demonstrates how to perform the power supply rejection ratio (PSRR) measurement on a voltage regulator using the Picotest J2120A line injector. Boehler defines PSRR, and discusses the pitfalls of the common approach to measuring PSRR (i.e. using an injection transformer to modulate an ac signal onto the input bus of a system.) He presents a test circuit consisting of a test board with an LM317 linear regulator, an ac-dc power adapter to power the regulator, a network analyzer to generate the ac test signal, the J2120A line injector, and the J211A current injector to load the test circuit. Boehler discusses setup, calibration, and measurements, which are performed with and without extra output capacitance, and the meaning of the measured results. The signal injector demonstrated can safely measure PSRR in systems with currents up to 5 A.

What you’ll learn:

• How to measure PSRR over a wide frequency range in systems with several amps of dc current.
• How to measure PSRR of voltage regulators using Picotest signal injectors
• How to understand limitations of injection transformers

Notes:

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Author & Publication:

Tom Boehler, Picotest, Vendor website, Mar 13 2011

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