A semiconductor package structure includes an organic substrate having a first surface, a first recess depressed from the first surface, a first chip over the first surface and covering the first recess, thereby defining a first cavity enclosed by a back surface of the first chip and the first recess, and a second chip over the first chip. The first cavity is an air cavity or a vacuum cavity.

An LC oscillator has a tank driver connected to cause a matched-resistance LC tank to oscillate. The LC tank has an inductor leg in parallel with a capacitor leg. The inductor leg has an explicit inductor having an implicit resistance level R.sub.L. The capacitor leg has an explicit capacitor having an implicit resistance level R.sub.C connected in series with an explicit resistor having an explicit resistance level R.sub.R, where R.sub.M=(R.sub.C+R.sub.R) is substantially equal to R.sub.L. The LC oscillator may have a non-trimmable LC tank and be part of a temperature-compensated frequency reference generator having standalone frequency adjustment circuitry that offers better than 0.1% frequency accuracy (after single trim and batch calibration) over process, voltage, and temperature variations, and lifetime, which can serve as a low-cost replacement for a crystal oscillator for many applications.

An LC oscillator has a tank driver connected to cause a matched-resistance LC tank to oscillate. The LC tank has an inductor leg in parallel with a capacitor leg. The inductor leg has an explicit inductor having an implicit resistance level R.sub.L. The capacitor leg has an explicit capacitor having an implicit resistance level R.sub.C connected in series with an explicit resistor having an explicit resistance level R.sub.R, where R.sub.M=(R.sub.C+R.sub.R) is substantially equal to R.sub.L. The LC oscillator may have a non-trimmable LC tank and be part of a temperature-compensated frequency reference generator having standalone frequency adjustment circuitry that offers better than 0.1% frequency accuracy (after single trim and batch calibration) over process, voltage, and temperature variations, and lifetime, which can serve as a low-cost replacement for a crystal oscillator for many applications.

A semiconductor package structure includes an organic substrate having a first surface, a first recess depressed from the first surface, a first chip over the first surface and covering the first recess, thereby defining a first cavity enclosed by a back surface of the first chip and the first recess, and a second chip over the first chip. The first cavity is an air cavity or a vacuum cavity.

A semiconductor package structure includes an organic substrate having a first surface, a first recess depressed from the first surface, a first chip over the first surface and covering the first recess, thereby defining a first cavity enclosed by a back surface of the first chip and the first recess, and a second chip over the first chip. The first cavity is an air cavity or a vacuum cavity.

A clock oscillator includes with a pullable BAW oscillator to generate an output signal with a target frequency. The BAW oscillator is based on a BAW resonator and voltage-controlled variable load capacitance, responsive to a capacitance control signal to provide a selectable load capacitance. An oscillator driver (such as a differential negative gm transconductance amplifier), is coupled to the BAW oscillator to provide an oscillation drive signal. The BAW oscillator is responsive to the oscillation drive signal to generate the output signal with a frequency based on the selectable load capacitance. The oscillator driver can include a bandpass filter network with a resonance frequency substantially at the target frequency.

A clock oscillator includes with a pullable BAW oscillator to generate an output signal with a target frequency. The BAW oscillator is based on a BAW resonator and voltage-controlled variable load capacitance, responsive to a capacitance control signal to provide a selectable load capacitance. An oscillator driver (such as a differential negative gm transconductance amplifier), is coupled to the BAW oscillator to provide an oscillation drive signal. The BAW oscillator is responsive to the oscillation drive signal to generate the output signal with a frequency based on the selectable load capacitance. The oscillator driver can include a bandpass filter network with a resonance frequency substantially at the target frequency.

A piezoelectric resonator unit includes a base member having a mounting surface. A piezoelectric resonator is mounted on the mounting surface and a lid member is bonded to the mounting surface such that the piezoelectric resonator is hermetically sealed in an inner space. A heat conductor is connected to a temperature sensor that detects a temperature of the piezoelectric resonator and is connected to a heating element that radiates heat onto the piezoelectric resonator. The heat conductor has a portion that is arranged in the inner space.

A piezoelectric resonator unit includes a base member having a mounting surface. A piezoelectric resonator is mounted on the mounting surface and a lid member is bonded to the mounting surface such that the piezoelectric resonator is hermetically sealed in an inner space. A heat conductor is connected to a temperature sensor that detects a temperature of the piezoelectric resonator and is connected to a heating element that radiates heat onto the piezoelectric resonator. The heat conductor has a portion that is arranged in the inner space.

An oscillator includes a board having a first surface, and provided with a housing section opening on the first surface, a resonator including a resonator element and a resonator package configured to house the resonator element, a heat generator attached to the resonator, electrically connected to the resonator package, and disposed inside the housing section, and a plurality of lead terminals connected to the board, and configured to support the resonator.