Oscillator apparatus and associated methods

A method of using an apparatus, the apparatus comprising a film bulk acoustic resonator and a field effect transistor:

• the film bulk acoustic resonator comprising first and second electrodes separated by a piezoelectric material, the piezoelectric material configured such that the application of a potential difference between the first and second electrodes enables the generation of an acoustic wave and associated surface charge in the piezoelectric material;
• and
• the field effect transistor comprising a channel, and source and drain electrodes configured to enable a flow of electrical current through the channel when a potential difference is applied between the source and drain electrodes, the field effect transistor being formed on the piezoelectric material of the film bulk acoustic resonator,
• wherein the first electrode of the film bulk acoustic resonator comprises electrically connected first and second portions, the second portion capacitively coupled to the channel of the field effect transistor via a dielectric material, and
• wherein the first portion of the first electrode is capacitively coupled to the piezoelectric material such that the surface charge generated in the piezoelectric material induces a corresponding charge in the first electrode which causes a variation in the electrical current flowing through the channel via the second portion of the first electrode, the variation in electrical current producing an output signal having a frequency which corresponds to that of the acoustic wave,
• the method comprising applying a potential difference between the first and second electrodes of the film bulk acoustic resonator to produce an output signal having a frequency which corresponds to that of the resulting acoustic wave.

A method of making an apparatus, the method comprising forming a film bulk acoustic resonator and a field effect transistor:

• the film bulk acoustic resonator comprising first and second electrodes separated by a piezoelectric material, the piezoelectric material configured such that the application of a potential difference between the first and second electrodes enables the generation of an acoustic wave and associated surface charge in the piezoelectric material;
• and
• the field effect transistor comprising a channel, and source and drain electrodes configured to enable a flow of electrical current through the channel when a potential difference is applied between the source and drain electrodes, the field effect transistor being formed on the piezoelectric material of the film bulk acoustic resonator,
• wherein the first electrode of the film bulk acoustic resonator comprises electrically connected first and second portions, the second portion capacitively coupled to the channel of the field effect transistor via a dielectric material, and
• wherein the first portion of the first electrode is capacitively coupled to the piezoelectric material such that the surface charge generated in the piezoelectric material induces a corresponding charge in the first electrode which causes a variation in the electrical current flowing through the channel via the second portion of the first electrode, the variation in electrical current producing an output signal having a frequency which corresponds to that of the acoustic wave.