Power distribution network (‘PDN’) noise is one of the most common issues in low power applications. Whether you are powering ADCs, clocks, LNAs, digital data networks or sensitive RF applications, properly tuning your power supply is of the utmost importance. Due to the interactions between the source and load impedance, the troubleshooting must be performed in-circuit and there is often very limited physical access. As a result, this can be a time consuming process. In this sample application note we show how Picotest probes and new J2150A Harmonic comb can be used optimize, test, and troubleshoot power integrity issues, such as clock jitter.