thumb|Three amplidynes, from a 1951 General Electric advertisement (not to same scale). (top left) 1 kW amplidyne motor–generator, (bottom left) 3 kW amplidyne motor–generator, (right) 5 kW amplidyne generator. thumb|Figure 1 of the patent drawing
thumb|Three amplidynes, from a 1951 General Electric advertisement (not to same scale). (top left) 1 kW amplidyne motor–generator, (bottom left) 3 kW amplidyne motor–generator, (right) 5 kW amplidyne generator. thumb|Figure 1 of the patent drawing
An amplidyne is an obsolete electromechanical amplifier invented prior to World War II by Ernst Alexanderson. It consists of an electric motor driving a DC generator. The signal to be amplified is applied to the generator's field winding, and its output voltage is an amplified copy of the field current. The amplidyne was used in industry in high power servo and control systems, to amplify low power control signals to control powerful electric motors, for example.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).