title: Amplifier
context: The first practical device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912.  Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when the transistor, invented in 1947, replaced them.  Today, most amplifiers use transistors, but vacuum tubes continue to be used in some applications.
question: When was the first power amplifier created?
answers: around 1912