Optoisolators with transistor photovoltaic output are electronic devices that combine optical and electrical isolation in a single component. They consist of a light source, a photodetector, and a transistor output stage. The light source emits light into the photodetector, which converts it into an electric current. This current is then amplified by the transistor output stage, providing a high degree of electrical isolation between the input and output circuits. These optoisolators are commonly used in applications where high-speed data transmission or signal conversion is required, such as in telecommunications systems, medical equipment, and industrial control systems.