Abstract: A multilayer piezoelectric transformer is provided using a composite vibration modes for step-up voltage conversion applications. An input portion polarized to deform radially is bonded to an output portion via a bondline or constraint layer. The deformation of the central face of the input portion is constrained by the bonded output layer or constraint layer. The output layer is bonded to the input layer or constraint layer and also deforms radially. The differing freedom of motion between the layers creates a gradient of stress and strain in the thickness direction resulting in large shear forces along the input and output layers. The composite radial-shear mode deformation of the output portion piezoelectrically generates an efficient, stepped-up high output voltage.