Equivalent Circuits with Piezo Losses

“Equivalent Circuits with Piezo Losses” expands the equivalent circuit approach in order to facilitate the experimental analysis easier. Mechanical and electrical systems are occasionally equivalent from the mathematical formula’s viewpoint. Therefore, an electrician tries to understand a mechanical system behavior from a more familiar LCR electrical circuit analysis. However, two important notes must be taken into account: (1) mechanical loss is handled as “viscous damping” and (2) equivalent circuit approach is almost successful, as long as we consider a steady sinusoidal (harmonic) vibration. When we consider a transient response, such as a pulse drive of a mechanical system with finite specimen size, the equivalent circuit analysis generates a significant discrepancy. The equivalent (electric) circuit (EC) is a widely used tool which greatly simplifies the process of design and analysis of the piezoelectric devices, in which the circuit can only graphically characterize the mechanical loss by applying a resistor (and dielectric loss sometimes). ¹ Different from a pure mechanical system, a piezoelectric vibration exhibits an “antiresonance” mode in addition to a “resonance” mode, due to the existence of the damped capacitance (i.e., only the partial of the input electric energy is transduced into the mechanical energy). Without introducing the piezoelectric loss, it is difficult to explain the difference of the mechanical quality factors at the resonance and antiresonance modes. We consider new equivalent circuits of piezoelectric devices with these three losses in this chapter.