Thickness mode vibration piezoelectric transformer

A thickness mode vibration piezoelectric transformer of a laminated structure comprising:

• a first thickness mode vibrator portion having a first piezoelectric layer interposed respectively between a first pair of electrode layers, said first piezoelectric layer being polarized in the direction of thickness thereof;
• and
• a second thickness mode vibrator portion stacked on said first thickness mode vibrator portion and having a second piezoelectric layer interposed between a second pair of electrode layers disposed parallel to said first pair of electrode layers, said second piezoelectric layer being polarized in the direction of thickness thereof, said first and second thickness mode vibrator portions have different impedances, a total thickness of said transformer in the direction perpendicular to said electrode layers being equal to half wavelength (.lambda./2) or one wavelength (.lambda.) of a driving frequency for said transformer, and at least three external terminals connected to said first and second pair of layers, an insulator layer being interposed between said first and second thickness mode vibrator portions, said insulator layer having a lower dielectric constant than the dielectric constant of said first and second piezoelectric layers and having a thickness which is smaller than 20% of said total thickness of said transformer.