Crystal oscillator with resistorless feedback biasing
US9209747B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 5, 2015 |
| Grant date | Dec 8, 2015 |
| Priority date | — |
| Expiry date | Feb 5, 2035 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03B2200/0066
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An oscillator includes an amplifier and a piezoelectric crystal coupled across a portion of the amplifier. A low pass filter (LPF) passes the common-mode voltage component of the crystal output signal. An auxiliary bias circuit uses a shared LPF component to charge a crystal load capacitor during start-up of the oscillator, and to provide a DC bias operating point to the oscillator driver transistor. A buffer amplifier receives the common-mode voltage component on the non-inverting input. The buffer amplifier output is coupled to both the inverting input and the drain terminal of the oscillator driver transistor such that the gate and drain DC bias voltages of the oscillator driver transistor are substantially the same. An automatic loop control circuit receives the crystal output signal and the common-mode voltage signal, and generates a bias control signal to bias the amplifier and the auxiliary bias circuit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.