Oscillator with fin field-effect transistor (FinFET) resonator
An integrated circuit may include oscillator circuitry having a resonator formed from fin field-effect transistor (FinFET) devices. The resonator may include drive cells of alternating polarities and sense cells interposed between the drive cells. The resonator may be connected in a feedback loop within the oscillator circuitry. The oscillator circuitry may include an amplifier having an input coupled to the sense cells and an output coupled to the drive cells. The oscillator circuitry may also include a separate inductor and capacitor based oscillator, where the resonator serves as a separate output filter stage for the inductor and capacitor based oscillator.
1. Oscillator circuitry comprising:
an oscillator having an oscillator output at which an oscillating signal is generated; and
a resonator configured to filter the oscillating signal and having
drive terminals coupled to the oscillator output,
sense terminals, and
fin field-effect transistor (FinFET) circuitry coupled to the drive and sense terminals, the FinFET circuitry including a substrate having a linear array of protruding fins characterized by a fin pitch that determines a resonant frequency of the resonator and being configured to generate acoustic waves that is in a subharmonic range of the resonant frequency.
2. The oscillator circuitry of claim 1 wherein the fin field-effect transistor (FinFET) circuitry comprises:
a gate conductor formed on the linear array of protruding fins and configured to:
extend in a direction perpendicular to each fin in the linear array of protruding fins;
form drive cells with respective groups of adjacent fins in the linear array of protruding fins such that the drive cells receive drive signals via the drive terminals to generate the acoustic waves; and
form sense cells with respective groups of adjacent fins in the linear array of protruding fins such that the sense cells are coupled to the sense terminals.
3. The oscillator circuitry of claim 2 wherein:
a first of the drive cells comprises a pair of adjacent fins in the linear array of protruding fins and is coupled to a positive drive terminal of the drive terminals;
a second of the drive cells comprises a pair of adjacent fins in the linear array of protruding fins and is coupled to a negative drive terminal of the drive terminals;
the pair of adjacent fins in the first of the drive cells are separated by a fin-to-fin spacing equal to the fin pitch minus the fin width; and
the first of the drive cells and the second of the drive cells are separated by an intervening region that extends a distance equal to four times the fin width plus five times the fin-to-fin spacing.
4. The oscillator circuitry of claim 2 wherein:
a first of the sense cells comprises a pair of adjacent fins in the linear array of protruding fins and is coupled to a positive sense terminal of the sense terminals and to a ground terminal;
a second of the sense cells comprises a pair of adjacent fins in the linear array of protruding fins and is coupled to a negative sense terminal of the sense terminals and to the ground terminal;
the pair of adjacent fins in the first of the sense cells are separated by the fin-to-fin spacing; and
the first of the sense cells and the second of the sense cells are separated by an intervening region that extends a distance equal to four times the fin width plus five times the fin-to-fin spacing.
5. The oscillator circuitry of claim 1 wherein oscillator comprises an inductor and a variable capacitor.
6. The oscillator circuitry of claim 5 further comprising:
a first capacitor coupling the oscillator output to a positive drive terminal of the drive terminals; and
a second capacitor coupling the oscillator output to a negative drive terminal of the drive terminals.
7. The oscillator circuitry of claim 6 further comprising:
a first bias resistor having a first terminal coupled to the first capacitor and having a second terminal configured to receive a bias voltage; and
a second bias resistor having a first terminal coupled to the second capacitor and having a second terminal configured to receive the bias voltage.
8. The oscillator circuitry of claim 1 further comprising:
a first transistor having a first source-drain terminal coupled to a positive sense terminal of the sense terminals, a second source-drain terminal, and a gate terminal that is configured to receive a bias voltage; and
a second transistor having a first source-drain terminal coupled to a negative sense terminal of the sense terminals, a second source-drain terminal, and a gate terminal that is configured to receive the bias voltage.
9. The oscillator circuitry of claim 8 further comprising an inductor having a first terminal coupled to the second source-drain terminal of the first transistor and having a second terminal coupled to the second source-drain terminal of the second transistor.
10. The oscillator circuitry of claim 8 further comprising an output buffer having a first input coupled to the second source-drain terminal of the first transistor and having a second input coupled to the second source-drain terminal of the second transistor.
11. The oscillator circuitry of claim 8 further comprising a level detector having inputs coupled to the first and second transistors and having an output coupled to a variable capacitor in the oscillator.
12. Oscillator circuitry comprising:
an oscillator having a variable capacitor and configured to output an oscillating signal; and
a resonator having an input configured to receive the oscillating signal from the oscillator and having an output that is coupled to the variable capacitor via a feedback path, the resonator having
drive terminals coupled to the oscillator output,
sense terminals, and
fin field-effect transistor (FinFET) circuitry coupled to the drive and sense terminals;
a level detector disposed in the feedback path, the level detector having inputs coupled to the output of the resonator and configured to output a signal for controlling the variable capacitor; and
an output buffer having inputs coupled to the level detector, wherein the resonator is coupled between the oscillator and the inputs of the output buffer.
13. The oscillator circuitry of claim 12 wherein the resonator is configured to filter the oscillating signal to produce a corresponding filtered signal.
14. The oscillator circuitry of claim 12 wherein the level detector is configured to detect a highest signal amplitude of the oscillating signal.
15. Oscillator circuitry comprising:
an oscillator having a quality factor;
a resonator configured to receive signals from the oscillator and to increase an overall quality factor of the oscillator circuitry to be greater than the quality factor of the oscillator, the resonator having
drive terminals coupled to an oscillator output,
sense terminals, and
fin field-effect transistor (FinFET) circuitry coupled to the drive and sense terminals;
a first capacitor coupling the oscillator output to a positive drive terminal of the drive terminals; and
a second capacitor coupling the oscillator output to a negative drive terminal of the drive terminals.
16. The oscillator circuitry of claim 15 further comprising a control circuit having an input coupled to the sense terminals of the resonator and having an output coupled to an adjustable component within the oscillator.
17. The oscillator circuitry of claim 16 wherein the fin field-effect transistor (FinFET) circuitry comprises a substrate having a linear array of protruding fins characterized by a fin pitch that determines a resonant frequency of the resonator and wherein the control circuit comprises a level detector configured to maintain operation of the resonator at the resonant frequency.