For today's communication circuits optimum operational conditions for almost every Tx power amplifier is one of the most important parameters. Only this will offer maximum power added efficiency and output power. For the experimental determination of these conditions load-pull measurements are the best solution. To compensate losses of the setup for on-wafer measurements an active load-pull measurement system is required. The Power Pull load-pull system combines all advantages of active load-pull measurements with an absolute stable configuration. It prevents oscillation of the measurement setup as well as of the transistor under test for large signal operation. Therefore, this configuration easily allows the complete characterization of transistors for optimum matching within power amplifiers.