The design and operation of ambipolar transistors and inverters were studied. In order to gain insights in the operation of ambipolar inverters an analytical model was developed which describes the electrical behavior of ambipolar transistors and inverters. The model was compared to experimentally realized inorganic and organic ambipolar thin-film transistors and inverters. Furthermore, the influence of the transistor parameters on the voltage transfer characteristics and the static noise margin are discussed. The model provides a general description which is applicable to a variety of ambipolar transistor technologies based on different material systems.