Abstract: A unit for suppressing harmonic vibration of a lower order which does not have desired frequency in an overtone resonator consisting main electrodes and sub electrodes. Harmonic vibration of a lower order suppressing piezoelectric vibrator comprises main electrodes arranged on a piezoelectric substrate and sub electrodes arranged in the vicinity of the main electrodes with gaps provided therebetween. If the electric equivalent circuit of the resonator is expressed by a coupling circuit which connects in series a circuit, which connects in parallel a series resonance circuit by the sub electrodes and coupling capacity indicating that the main electrodes are coupled with the sub electrodes, to a series resonance circuit by the main electrodes, then their loop frequencies substantially coincide with each other.

Abstract: A piezoelectric transformer includes a substrate of piezoelectric material, preferably a single crystal of LiNbO.sub.3. The substrate is uniformly polarized in a selected direction thereof and vibrated in a direction of the length thereof. An input voltage is applied across both sides of a portion of the substrate in a direction of the thickness thereof and thus excites a vibration by way of piezoelectric effect. Thereby another voltage is caused in the direction of the thickness of the substrate in a portion other than the portion to which the input voltage is applied, and taken out as an output voltage. As a result, it is possible to decrease the output impedance to obtain a large load current and thus fully heighten a step-up ratio of the piezoelectric transformer.