This paper presents experiments on a piezoelectric energy harvester driven by broadband vibrations. The energy harvester is investigated both with and without a mechanical end stop that limits proof mass motion. The end stop increases the effective bandwidth at large acceleration amplitudes. For sinusoidal vibrations, the mechanical end stop causes the output power to reach a plateau at a critical acceleration amplitude and does not increase significantly with increasing acceleration amplitude. In contrast, the output power increases with increasing spectral density of the broadband vibration, though at a smaller rate in the presence of an end stop. The optimal load for broadband vibrations is different from either of the two optimal loads for sinusoidal vibrations.
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