Active filter for providing improved notch and band pass filters
US4156853A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 9, 1978 |
| Grant date | May 29, 1979 |
| Priority date | — |
| Expiry date | Feb 9, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H11/1217
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An active filter is disclosed for providing improved notch and band pass filters. The output to input frequency response of an active filter is mathematically expressed as a ratio of two polynominals in the Laplace operator S. In any notch filter, the coefficient of the S term in the numerator must be reduced to zero, while in any band pass arrangement the coefficient of the S term in the denominator is reduced to zero. The improved notch filter provides an input circuit for the operational amplifier portion of the filter which eliminates the S term in the numerator so that adjustments to reduce this term are unnecessary. Similarly, in the improved band pass filter, the S term in the denominator is eliminated in the feedback circuit provided for the operational amplifier, so that adjustment is unnecessary to eliminate the coefficient of S.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.