Abstract: In one example, an audio device includes a substrate, a first piezoelectric flap, a second piezoelectric flap, a transmit circuit, a first receive circuit, a switch circuit, and a second receive circuit. The substrate has an opening. The first piezoelectric flap has a first end on the substrate and extending over the opening, the first piezoelectric flap having first and second terminals. The second piezoelectric flap has a second end on the substrate and extending over the opening, the second piezoelectric flap spaced from the first piezoelectric flap, the second piezoelectric flap having third and fourth terminals. The transmit circuit has driver outputs. The first receive circuit has first receiver inputs. The switch circuit coupled to the driver outputs and the first receiver inputs, and the first and second terminals. The second receive circuit has second receiver inputs coupled to the third and fourth terminals.

Abstract: In one example, an apparatus comprises a substrate, a first piezoelectric flap, and a second piezoelectric flap. The substrate has an opening. The first piezoelectric flap has a first end on the substrate and has a first portion extending over a first part of the opening, the first piezoelectric flap including first electrodes, in which the first electrodes extend no more than half of a first length of the first portion. The second piezoelectric flap has a second end on the substrate and has a second portion extending over a second part of the opening, the second piezoelectric flap including second electrodes, in which the second electrodes extend no more than half of a second length of the second portion.

Abstract: An apparatus comprises a piezoelectric resonator, a first active inductor circuit, and a second active inductor circuit. The piezoelectric resonator includes a first resonator terminal and a second resonator terminal. The first active inductor circuit is coupled between the first resonator terminal and a power supply terminal, the first active inductor circuit having a first impedance that reduces with a first frequency where the first frequency is at or above 1 GHz. The second active inductor circuit is coupled between the second resonator terminal and the power supply terminal, the second active inductor circuit having a second impedance that reduces with a second frequency where the second frequency is at or above 1 GHz.

Abstract: An oscillator circuit includes a bulk acoustic wave resonator, a differential active inductor circuit, and a gain circuit. The differential active inductor circuit is configured to bias the bulk acoustic wave resonator. The differential active inductor circuit is coupled between the bulk acoustic wave resonator and a power supply terminal. The gain circuit is coupled to the bulk acoustic wave resonator.

Abstract: In examples, a semiconductor die comprises a semiconductor substrate having a surface, the surface having first and second surface portions, and a radiator layer on the surface. The radiator layer comprises a metal member having a first metal member portion above the first surface portion and a second metal member portion above the second surface portion, a first distance between the first metal member portion and the first surface portion, and a second distance between the second metal member portion and the second surface portion, the first distance less than the second distance. The radiator layer includes first and second electrodes. The radiator layer includes a piezoelectric layer extending along a length of the radiator layer and on each of the first and second electrodes, the piezoelectric layer between the first and second metal members and the semiconductor substrate.

Abstract: An oscillator circuit includes a bulk acoustic wave resonator, a differential active inductor circuit, and a gain circuit. The differential active inductor circuit is configured to bias the bulk acoustic wave resonator. The differential active inductor circuit is coupled between the bulk acoustic wave resonator and a power supply terminal. The gain circuit is coupled to the bulk acoustic wave resonator.

Abstract: A microelectromechanical systems (MEMS) resonator includes a substrate, an array of ferroelectric capacitors on the substrate, and a three-dimensional metal stack above the array of ferroelectric capacitors. The three-dimensional metal stack may include more than two metal layers. Each of the metal layers is coupled to another of the metal layers by more than two metal vias.