In general, the range of applications for large-area electronics or macroelectronics is limited by the quality of the semiconductor used to make the electronic devices and circuits. Here, we address the question of how to make high-performance transistors using semiconductors that are defective, have low carrier mobilities, and are unstable. It is proposed that we need to engineer and operate a transistor that minimizes the excess carrier concentration throughout the device. combined with high internal fields over small dimensions. Compared with the field-effect transistor, a source-gated transistor more nearly meets these requirements. Using the unstable and defective semiconductor, hydrogenated amorphous silicon, it is shown that high-performance thin-film transistors can indeed be made using the source-gated concept.