Figure 9.

The characteristics of close-loop oscillation of piezoelectric cantilever resonator and the simulated result. (a) The frequency fluctuation of the resonator within two hours—the resonance frequency is reduced by 0.2 Hz; (b) the Allan deviation of the resonator within two hours—the minimal Allan deviation is 15.45 ppb; (c) the time domain wave of the output voltage of the driving port, the 2nd operational amplifier, and amplitude limiter; (d) the tip displacement with FEM simulation—the tip displacement is 2.09 nm.