An amp was a unit of measurement for an electric current.
In 2368, William T. Riker questioned if Data's body could withstand a half a million amps would flowed it as a nonconductor. Data indicated that such a power surge would cause a system failure in his internal processors and melt his primary power couplings. (TNG: "Disaster")
In 2374, the miniature Miles O'Brien warned the miniature Julian Bashir, who were both inside an optronic circuit, not to touch a nearby chip because it carried 20 microamps of electric current, which normally wasn't very much, but would be sufficient to fry every synapse in the body of a person who was only one centimeter tall. (DS9: "One Little Ship")