Power amplifiers are one of the most power consuming building blocks in mobile communication systems. Moreover, the number of power amplifiers used in communication systems keeps rising. As such, they have a large influence on the carbon footprint of our communication systems. Besides, the 5th generation of mobile networks is making use of much higher carrier frequencies at 28 GHz, where power amplifiers are less efficient, certainly when a high linearity is required. To overcome this, this project will research the use of an out-phasing power amplifier which is driven by a discrete set of different phases. Using two power amplifiers that output a signal with constant amplitude but different phases, an arbitrary modulated signal can be obtained. However, the individual power amplifiers can be made much more efficient because they can be non-linear. By properly designing the combining network, high efficiency over a wide range of output powers can be realized and parasitic capacitance of the individual amplifiers can be included in it. A problem with out-phasing is that the phases of the input signals need to be very accurate. To circumvent this, only a discrete set of input signals will be applied, which are originating from a complex sigma-delta modulator and a phase mapper. As such non-linearity can be mitigated and a very easy drive circuit can be designed ensuring little added power consumption and area.