Amplification of longitudinal acoustic waves traveling in a thin piezoelectric ceramic plate was achieved by electrically coupling the elastic waves to the drifting carriers in ann‐silicon plate. Amplification up to 15 dB/cm in the 2‐MHz range was obtained, and the system was also operated as a tunable oscillator and mixer in the 0.5‐ to 4‐MHz range. In addition, these experiments also enabled us to measure the drift mobility of majority carriers in silicon.