Oscillator circuit with high pass filter and low pass filter in output stage
US7362190B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 9, 2005 |
| Grant date | Apr 22, 2008 |
| Priority date | — |
| Expiry date | Mar 6, 2026 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03B5/366
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An integrated circuit has an internal oscillator circuit for being connected to an external frequency source such as a crystal or a ceramic resonator. The internal oscillator circuit has an inverting amplifier across the frequency source terminals to establish an oscillation there. One terminal of the frequency source is coupled to one input of the comparator and to a second input of the comparator through a low pass filter. Coupling the output of the low pass filter to the second input of the comparator is for preventing a DC offset from developing between the two inputs of the comparator. The other terminal of the frequency source is coupled to the second input of the comparator through a high pass filter. The high pass filter provides the comparator with a larger voltage differential to increase noise margin. Noise margin is further improved by allowing an increase in hysteresis in the comparator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.