This dissertation describes a MEMS-based frequency-selective power ampliﬁer that performs both signal ﬁltering and power ampliﬁcation, while consuming zero power when there is no input, i.e., zero-quiescent power consumption. The frequency-selective power ampliﬁer employs a micromechanical resonant switch (resoswitch) as a key building block similar to those recently used for zero-quiescent power radio receivers, but capable of handling higher powers. This document details the design, fabrication, and characterization of these higher frequency and higher power micromechanical resoswitches, and employs them as power ampliﬁers. Here, the mechanical Q of the resoswitch largely governs the threshold input level that instigates power gain. Theoretical and experimental studies of Q, as well as Q enhancement techniques and high-Q structural design, are discussed. Further, post-fabrication laser trimming addresses the frequency accuracy of the vibrating devices. A model that replaces laser blasted holes with stiﬀness-modifying cracks captures well the frequency shift dependence on laser blast location. The accuracy of this theory further enables a deterministic trimming protocol that speciﬁes the laser targeting sequence needed to achieve a required amount of frequency tuning with minimal Q reduction.